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View Full Version : Sharpening HSS w/diamond---'thought that was a no-no



Arthur.Marks
08-27-2011, 03:09 PM
I have acquired the impression that all diamond wheels are unsuitable for (primary) use on HSS (or steel in general). So why aren't these?

"GRS Power Hone uses diamond wheels to sharpen hardened steels, high speed steels and carbides. You can now choose the best tool material for each job because you can sharpen them all."
http://www.grstools.com/tool-sharpening/power-hone/power-hone-basic.html

Can someone explain the apparent contradiction?

kendall
08-27-2011, 03:12 PM
Think it would primarily depend on the surface speed. Slow speed makes a diamond great at sharpening.

Arthur.Marks
08-27-2011, 03:18 PM
The manual lists 240rpm for the spindle with a 5" diameter wheel (diamond) or 6" diameter lap (ceramic).

Black_Moons
08-27-2011, 03:23 PM
Yep, surface speed... I wonder if anyone can figure out exactly what SFM before diamonds start to (quickly?) dissolve into steel/hss?

(Its not the heat of the wheel, but the heat of the microscopic point of contact)

Sorta like how over 100SFM with HSS verus steel tends to degrade the HSS quickly, even though the bulk HSS does not heat up much, the atoms at the actual cutting edge become superheated untill they lose strength. (At least, I think thats why higher SFM degrades HSS?)

lynnl
08-27-2011, 04:05 PM
I think the whole notion of steel grinding quickly eroding diamond stones/wheels is largely a myth, or at least greatly oversold. Industry does it all the time.

Evan
08-27-2011, 05:33 PM
I think the whole notion of steel grinding quickly eroding diamond stones/wheels is largely a myth, or at least greatly oversold. Industry does it all the time.

It's not a myth according to Norton. Industry uses flood coolant.

http://ixian.ca/pics9/norton_tip.jpg

http://www.nortonindustrial.com/uploadedFiles/SGindnortonabrasives/Documents/Catalog_PDFs/NortonSuperabrasives-NortonToolroomWheels.pdf

.RC.
08-27-2011, 06:13 PM
Diamond wheels cost what $20 a pop..... CBN costs probably $100 a pop... (they are bloody expensive compared to diamond)

I go with diamond...

Arthur.Marks
08-27-2011, 06:22 PM
So what I am hearing is that there is a generalization of warning being made. Just about every bench grinder, so-called 'carbide grinder', surface grinder or T&C grinder runs at or above 1800rpm---and more often at or above 3600rpm. Given this, the generalization is to never use diamond wheels for sharpening... on such a machine. The more accurate warning is to not use diamond wheels above __ sfm while grinding HSS/steel. Below ___ sfm diamond is quite useful for sharpening HSS/steel. I can follow that. I mean, diamond paste is routinely used for final lapping and honing which is a low-speed operation. For example, brass expanding lap used with diamond paste to finish a hardened steel bore.

Arthur.Marks
08-27-2011, 06:25 PM
Diamond wheels cost what $20 a pop..... CBN costs probably $100 a pop... (they are bloody expensive compared to diamond)

I'm not sure what is implied with your statement with regards to CBN (cubic boron nitride). I have seen this designation, but I know next to nothing regarding its use.

[EDIT] Okay, reading further into the Norton link, I see they recommend CBN for use on HSS. Got it.
"Norton B99 cBN Wheels • Sharpening high-speed (M2,D2,T15,etc.) steel cutting tools • Surface and ID grinding hardened steel die components • Precision grinding steel parts Rc50 or harder"

Tanto
08-27-2011, 06:26 PM
Diamond is commonly used for sharpening HSS in industry and consumer products. The Drill Doctor is one example everyone here would be familiar with that uses a diamond coated wheel. Many commercial T & C grinders are now also sold with a diamond wheel as standard.

John Stevenson
08-27-2011, 06:52 PM
In theory it's probably correct.

In practice the problem doesn't occur. I have had a 4" diamond grinding wheel on my T&C grinder now about 4 years now and can't see any degrading from new. In fact I bought a spare wheel expecting this not to last.

Even if it only lasted a few months, at £10 a pop they are just consumables but this is not happening.

ammcoman2
08-27-2011, 07:04 PM
+1 with John's comment.

I use 4" diameter diamond wheels running at about 3400rpm on my home made T&C grinder. Also have a 3 3/4" CBN wheel. They are #150 grit and the results appear to be very similar. I am not, however, running at "industrial rates of removal". I can't tell if there is any difference using the diamond wheels on carbide or HSS.

There may be a difference using a 6" wheel at these speeds but I am not planning a test any time soon.

Geoff

davidwdyer
08-27-2011, 08:38 PM
That GRS power hone looks like an extremely over priced little thing. I believe many lapidary shops or catalogs would sell something equal for much less.

Arthur.Marks
08-27-2011, 08:47 PM
Am not interested in the machine itself. I was just baffled by the diamond wheel use description.

Evan
08-27-2011, 08:59 PM
So what I am hearing is that there is a generalization of warning being made.

No need to get really fussy about it. If a diamond wheel is throwing sparks on steel then it is getting hot enough to damage the diamonds faster than normal.

A lot depends on the wheel itself. Electroplate diamond wheels will withstand cutting steel better than resin bond wheels. The electroplate wheel has the grit in close contact with the metal substrate which helps keep the diamonds cool.

Diamonds are a metastable material which means that the stability is temperature dependent. Diamonds eventually revert to graphite even at room temperature. At room temperature it takes a very long time, many millions of years. At elevated temperatures at around 1000F they last only minutes. Higher than that they break down very rapidly in seconds or milliseconds.

What helps to save them is that diamond conducts heat about 4 to 5 times better than silver. This helps to keep the cutting tip cool by transferring the heat to the bulk material around the diamond.

What affects the lifetime of any particular diamond wheel used on steel is a number of variables. The higher the grit concentration the better the wheel dissipates heat to the substrate. This is especially the case with resin bond wheels and the cheap wheels have low concentrations of maybe 50%. High quality wheels will be 75% to 100%.

At 100% the binder fills only the gaps between the grit which is packed as tightly as possible. This greatly improves conduction and these are the types of wheels used in industry.

Also, industry uses flood coolant when grinding and that keeps the temperature of the grit under control.

Blanket statements about what industry uses are meaningless without qualification as to what industry really uses.

Tanto
08-27-2011, 09:11 PM
This greatly improves conduction and these are the types of wheels used in industry.

Also, industry uses flood coolant when grinding and that keeps the temperature of the grit under control.

Blanket statements about what industry uses are meaningless without qualification as to what industry really uses.


It's not a myth according to Norton. Industry uses flood coolant.

Do you mean blanket statements like those?

Evan
08-27-2011, 10:14 PM
Industry uses flood coolant.

That isn't a blanket statement. The subject is using diamond to grind steel, a very narrow part of the abrasives world.

lazlo
08-27-2011, 10:29 PM
Am not interested in the machine itself. I was just baffled by the diamond wheel use description.

It's a surface speed thing. In order to dissolve diamond, the local heat has to be above a considerable temperature. Maybe someone who cares will Google it :)

The diamond power laps like that GRS and the Glendo intentionally run at a very slow speed to avoid the temperature issue. So slow that it's irritating to shape the blade with them -- they're more for honing.

By the way, the GRS looks like a repackaged Accu-Finish I. I mentioned on PM that after using an Accu-Finish I and II, side-by-side, for 30 hours at Rich King's scraping class, I wasn't impressed. It's a little belt driven motor in a thin sheetmetal box. Nothing like a Baldor 500.

Evan
08-27-2011, 10:35 PM
I use diamond to grind steel (and carbide) frequently. The machine I use is a horizontal grinder that turns a 12" diamond wheel at about 200 rpm. Even then I use water lubricant because it cuts much faster. As long as the wheel and the grit stays cool it isn't an issue.

lazlo
08-27-2011, 10:38 PM
The machine I use is a horizontal grinder that turns a 12" diamond wheel at about 200 rpm. Even then I use water lubricant because it cuts much faster. As long as the wheel and the grit stays cool it isn't an issue.

That's very close to the Glendo, which turns a 5 or 6" wheel at 300 rpm. You can rub your finger on the Glendo, it turns so slow :)

When you try to shape carbide with a 300 grit wheel, it sounds like a thousand kids rubbing gravel on a chalk board. IMHO, the best setup would be a Baldor 500 for shaping the edge, and using the hone to touch it up.

J Tiers
08-27-2011, 10:39 PM
Suit yerself...

I have an old, old Glendo, and it does a great job shaping HSS, AND carbide. best thing I ever used for scraping blades.

it shapes carbide in a hurry, you gotta watch what you are doing, and that is with a finer wheel. I got several wheels with it.

The coarsest wheel does a relatively decent fast job on HSS lathe cutters.

But, to go along with what Evan said, the Glendo is intended to run WET. You spray the wheel with their special stuff.... or if you are me, you put a tad of detergent in water as a wetting agent, and use in a spray bottle....

Speed? Depends what you want with it. If you are doing scraping blades, you want a medium fine wheel at least. Those naturally cut slower, but give a good finish.

Still fast enough for me, for sure.

lazlo
08-27-2011, 10:42 PM
it shapes carbide in a hurry, you gotta watch what you are doing, and that is with a finer wheel.

Your idea of "a hurry" must be different than mine. It takes a long time to shape the radius of a new scraper blade on the Accu-Finish with the 360 grit wheel.

When Don Thomas first got his, he was posting on PM asking if sharpening on the Glendo was supposed to be that slow :)

Evan
08-27-2011, 10:45 PM
Mine is one I built by converting an industrial shaker table to a horizontal grinder. The wheel came from the business my wife manages. It is a $1000 profile wheel that was worn on the edge but untouched on the sides.

http://ixian.ca/pics9/hgrinder1.jpg

Oh, it cuts carbide in a hurry.

lazlo
08-27-2011, 10:54 PM
I just did the math Evan, and your power lap is almost twice the SFPM at the edges as the Glendo:

628 SFPM for a 12" wheel at 200 RPM versus 392 for the Glendo.

Black_Moons
08-27-2011, 10:59 PM
I just did the math Evan, and your power lap is almost twice the SFPM at the edges as the Glendo:

628 SFPM for a 12" wheel at 200 RPM versus 392 for the Glendo.

Where did evan say how many RPM's his power lap is?

Also theres a control on it, I wonder if thats motor speed, or a timer?

Arthur.Marks
08-27-2011, 11:01 PM
...with a 300 grit wheel, it sounds like a thousand kids rubbing gravel on a chalk board.
For some reason, I found the above both an excruciating and absolutely hilarious statement. :p

I just didn't know the specifics. All I've ever heard is 'no-no-no', for example, on something like the Baldor 500 grinder mentioned. What I am reading here is as long as you kept the coolant running through that mounted cup reservoir, you'd be fine using a Baldor 500 for HSS. Right? I've never used a diamond wheel for anything. The only diamond-ish thing in my shop is a dressing stick for Alum Ox. wheels.

lazlo
08-27-2011, 11:06 PM
Where did evan say how many RPM's his power lap is?

http://bbs.homeshopmachinist.net/showpost.php?p=694019&postcount=19

"The machine I use is a horizontal grinder that turns a 12" diamond wheel at about 200 rpm."

Arthur.Marks
08-27-2011, 11:12 PM
If a diamond wheel is throwing sparks on steel then it is getting hot enough to damage the diamonds faster than normal. Electroplate diamond wheels will withstand cutting steel better than resin bond wheels. The electroplate wheel has the grit in close contact with the metal substrate which helps keep the diamonds cool... Diamonds are a metastable material which means that the stability is temperature dependent... At elevated temperatures at around 1000F they last only minutes. Higher than that they break down very rapidly in seconds or milliseconds... diamond conducts heat about 4 to 5 times better than silver. This helps to keep the cutting tip cool by transferring the heat to the bulk material around the diamond... What affects the lifetime of any particular diamond wheel used on steel is a number of variables. The higher the grit concentration the better the wheel dissipates heat to the substrate. This is especially the case with resin bond wheels and the cheap wheels have low concentrations of maybe 50%. High quality wheels will be 75% to 100%... flood coolant when grinding... keeps the temperature of the grit under control.
Understanding the actual physics involved answers a lot for me. The above is very helpful; Thank you.

Tanto
08-27-2011, 11:14 PM
If it's simply a question of temperature of the diamond doing the damage, why can they sharpen other materials (for example carbide) without damage?

Arthur.Marks
08-27-2011, 11:16 PM
Good point, Tanto. (score one for Tanto!:D)

Tanto
08-27-2011, 11:26 PM
It was of course a loaded question Arthur ;)

Here's a hint to the answer. Carbon and carbon :p

Arthur.Marks
08-27-2011, 11:37 PM
Hmmm...
Thoughts on the table include HSS has a relatively high carbon content. Diamonds are carbon. BUT carbides are a carbon compound so I'm figuring they have a higher carbon content than HSS. Perhaps the bonding agent in carbide tooling and its brittleness tend to "break off" (aka grind) the work material easier whereas with HSS it stays together and that toughness needs more friction to "grind" it off? Or something like that... :) (i have no idea what I'm talking about! haha)

wierdscience
08-27-2011, 11:38 PM
Diamond burns at approximately 1500*F IIRC,aggressive dry grinding will literally "burn" the Diamonds whether your grinding steel,carbide or glass.The damage done isn't immediately apparent.It shows up as a decrease in efficiency and an increase in cutting pressure since the cutting faces are being rounded off.
At work we average 350-500sq inches of carbide being faced off .010-.035" deep per week in the form of plastic pelleting dies being re-surfaced.A 5" face wheel lasts us 6-7months running under flood coolant.If we ran the wheel dry it would be worn bare in a week or less.

When in doubt run coolant.

Black_Moons
08-28-2011, 12:58 AM
Hmmm...
Thoughts on the table include HSS has a relatively high carbon content. Diamonds are carbon. BUT carbides are a carbon compound so I'm figuring they have a higher carbon content than HSS. Perhaps the bonding agent in carbide tooling and its brittleness tend to "break off" (aka grind) the work material easier whereas with HSS it stays together and that toughness needs more friction to "grind" it off? Or something like that... :) (i have no idea what I'm talking about! haha)

Its that the carbon dissolves INTO the hss. (or steel)

Carbon does not dissolve into carbide, since its a compound and not an alloy.

tdmidget
08-28-2011, 01:08 AM
If it's simply a question of temperature of the diamond doing the damage, why can they sharpen other materials (for example carbide) without damage?

You know, some of you guys are like little kids asking "why is the sky blue". You atart off talking about grinding steel with diamond and then want to know whay what you don't believe would not not apply to Tungsten carbide. Apples and Oranges, that's why.
Carbon (as in diamond, dissolves in iron). There is no iron in tungsten carbide,duhhhhhhhhhhhhhh.
As to why junk machines like the drill doctor and the crappola hone whatchamacallit might get away with it, Pay attention!!!!
Grinding and honing/lapping are NOT the same thing. Furthermore you will find, if ye seek, that there are those who call CBN diamonds because, after all , they are both super abrasives, aren't they?
I just can;t see why this is so hard to comprehend.

tdmidget
08-28-2011, 01:25 AM
[quote=Black_Moons]Its that the carbon dissolves INTO the hss. (or steel)

Carbon does not dissolve into carbide, since its a compound and not an alloy.[/quote

Water is a compound, does sugar dissolve in to it?

Iron is not a compound, it's an element. Carbon does dissolve in iron. That's how steel is made. And , for that matter, grey iron.
What matters here is the behavior in the grinding zone, where temperatures may exceed 6000 degrees F. Coolant does not affect this significantly. It removes heat from the work and the wheel but without this heat grinding does not occur. At lower speeds material is still removed, albeit much slower. The heat in grinding is the result of surface speed. If the speed isn't there then material may indeed be removed, though much slower and with less heat generated. You can remove material with a stone, as in sharpening a pocket knife but that is not grinding. It is at grinding temperatures that carbon dissolves into the iron.

Tanto
08-28-2011, 02:48 AM
You know, some of you guys are like little kids asking "why is the sky blue". You atart off talking about grinding steel with diamond and then want to know whay what you don't believe would not not apply to Tungsten carbide. Apples and Oranges, that's why.
Carbon (as in diamond, dissolves in iron). There is no iron in tungsten carbide,duhhhhhhhhhhhhhh.
As to why junk machines like the drill doctor and the crappola hone whatchamacallit might get away with it, Pay attention!!!!
Grinding and honing/lapping are NOT the same thing. Furthermore you will find, if ye seek, that there are those who call CBN diamonds because, after all , they are both super abrasives, aren't they?
I just can;t see why this is so hard to comprehend.

Could we have that again ... in English?

.RC.
08-28-2011, 03:54 AM
All this discussion and not many people seem to get it....

Go price a diamond wheel and go price a CBN wheel..

I am going to continue using diamond wheels when sharpening my HSS wheels and if I somehow wear out 3 diamond wheels to a single CBN wheel I am still miles ahead...

John Stevenson
08-28-2011, 06:13 AM
The point is RC, you won't.

Regardless of all that's written which I don't take issue with but I have my own proof as opposed to theory.

Just shot out into the shop and took some snaps.

http://www.stevenson-engineers.co.uk/files/Diamond_wheel1.jpg

This is the wheel on my grinder after at least 4 years, possibly over 5 and it's in regular use, not a part time home shop.

http://www.stevenson-engineers.co.uk/files/Diamond_wheel2.jpg

Side view, sorry not too clear but you can still see the depth of the coating.

http://www.stevenson-engineers.co.uk/files/Diamond_wheel3.jpg


Brand new wheel, side view, never been fitted but gives a comparison to the thickness.

http://www.stevenson-engineers.co.uk/files/Diamond_wheel4.jpg

This is the machine we are talking about, the generic Chinese Universal tool and Cutter Grinder, which it is not !
Runs at 3,000 rpm and I use this just as an off hand grinder for tool bit and touching milling cutters up to get a second life before binning them.

The boxes above the machine are all brand new wheels been there 4 years or more waiting for this one to give up the ghost, Somewhere in the shop i have a CBN wheel which cost me about £100 but it's 5" and won't fit this grinder.
Chances are it won't get used at all.

Sorry I can't offer any theory or speculation, I can only offer my personal experiences.

wierdscience
08-28-2011, 10:13 AM
The simple reason John is in your apllication you simply aren't generating enough heat to do damage.No more heat than enough to make hand holding painful won't do any damage.If it were tied down in say a surface grinder that would be another story.

So maybe it's not a problem to grind steel with Diamond unless it's hogging off material at a commercial feedrate.

J Tiers
08-28-2011, 10:25 AM
Your idea of "a hurry" must be different than mine. It takes a long time to shape the radius of a new scraper blade on the Accu-Finish with the 360 grit wheel.



it isn't FOR "hogging out" shapes. I'd call that a silly complaint

When you touch up the edge, though, you have to watch out or you will grind off more than you need to.

lazlo
08-28-2011, 11:09 AM
it isn't FOR "hogging out" shapes. I'd call that a silly complaint

When you touch up the edge, though, you have to watch out or you will grind off more than you need to.

Ah, yes -- total agreement. Like I said earlier, the ideal setup would be a Baldor 500 carbide grinder to shape the blade, and a Glendo with a 600 or 1200 grit wheel to touch it up.

lazlo
08-28-2011, 11:17 AM
So maybe it's not a problem to grind steel with Diamond unless it's hogging off material at a commercial feedrate.

Like I said earlier, it's surface feet per minute thing.

As far as the mechanism, iron is a solvent for diamond. Obviously, the temperature of the reaction has a minimum threshold - if you sprinkle iron oxide on your wife's ring, it's not going to dissolve it away.

So you need to grind/hone steel at a low enough speed to keep the diamond below the critical temperature, or use coolant. Or just use the diamond wheel above the critical temperature and allow the iron to dissolve some of the diamond. The industry literature I've read never says how fast the reaction is - i.e., how quickly the diamond will erode. It's very possible that it erodes slow enough that a home shop guy would never notice.

Evan
08-28-2011, 12:22 PM
If it's simply a question of temperature of the diamond doing the damage, why can they sharpen other materials (for example carbide) without damage?


They can't. That's why they are still selling diamond wheels. The damage is greatly accelerated when sharpening steel.

Robert, in industry the emphasis is on stock removal rates. They don't care how long the wheel lasts in absolute terms as long as it is profitable. Industry also makes a lot of use of creep feed grinding with grinding depths of nearly the same as the entire depth of the grit layer. Taking off 0.1" in a single pass is common. I've tried it myself and it sure speeds up the job at the cost of greater wear. BUT, the wear per pass isn't greater than the time cost of many passes.

rode2rouen
08-28-2011, 12:50 PM
I have acquired the impression that all diamond wheels are unsuitable for (primary) use on HSS (or steel in general).


Old wives tale.
A diamond wheel puts a very nice edge on both HSS and brazed carbide with my old Cold Grind machine ($80.00 from a local seller on CL....Gloat).

Low speed (700 rpm in the case of the Cold Grind) seems the key.
Rough shaping done (carefully) on a bench grinder, finish work on the Cold Grind.

I use it to touch up TIG welding electrodes as well, works a treat.


Rex

http://i721.photobucket.com/albums/ww216/bjorn_toulouse/cold%20grind/cold02.jpg

http://i721.photobucket.com/albums/ww216/bjorn_toulouse/cold%20grind/cold03.jpg

Arthur.Marks
08-28-2011, 12:55 PM
Thank you all. This is very informative for me. Not only did I gain a better understanding of abrasive diamond use but a little metallurgy as well. By that I mean, a better distinction between an alloy (mixture of elements) versus a compound (chemically bonded substance). The latter cannot be separated or joined by physical processes alone. Energy is needed. The former can be made through mechanical means alone.

At a basic level, it seems this is the distinction which separates steel from carbide and their differing reactions to diamond abrasives. Both will erode--or wear---a diamond wheel. Both will do so in a unwanted, expedient manner above ~1300-deg. F (source (http://en.wikipedia.org/wiki/Diamond)). The diamonds lose their crystalline structure and revert to graphite. Below that, however, I am a little foggy in one regard. At what "high-temperature created by high-speed machining" (source (http://en.wikipedia.org/wiki/Diamond)) does carbon become soluble in iron? I am led to believe it is perhaps below the 1300-deg. F at which diamond converts to graphite. If it wasn't, both carbide and HSS would create excessive wear at the same temperature threshold whether one dissolved into the other or not.

Evan
08-28-2011, 01:10 PM
Diamond doesn't convert to graphite instantly. The rate at which it does is temperature dependent and because of the very high thermal conductivity of diamond the actual contact temperature can be very much higher than that required to promote a very fast conversion.

The solubility is what makes the difference since the temperature at which iron throws sparks may be even higher than 2000F at the point of impact. The nearly molten material dissolves a tiny bit of diamond at each point of impact whereas carbide does not become molten at those temperatures and does not generate sparks.

Note also that grinding high carbon steels with diamond does not cause the same damage as grinding low carbon steels.

Arthur.Marks
08-28-2011, 02:58 PM
Okay, I follow. The actual temperature at the cutting point of the abrasive grit and work can easily exceed 1300-deg.F. The diamond does not necessarily retain this heat (energy) long enough for its structure to deteriorate because it has the "highest... thermal conductivity of any bulk material." (source (http://en.wikipedia.org/wiki/Diamond)) The diamond is able to dissipate the heat with great efficiency compared to HSS. Whereas the HSS becomes molten due to the temperature (sparks), the diamond is able to retain its physical state even as it is in direct contact with +1300-deg. F temperatures. So what actually goes into solution? Does the molten spark dissolve some of the diamond grit and they both fall away from the wheel? Or does the molten spark dissolve into the wheel and thus rob it of its cutting efficiency? I am picturing the latter being like using brass on a bench grinder and loading the wheel.

[EDIT:]
re-reading Evan's statement above:

The nearly molten material dissolves a tiny bit of diamond at each pint of impact.
So is my statement,

the molten spark dissolve[s] some of the diamond grit and they both fall away from the wheel
correct or does the diamond get absorbed into the workpiece?

Evan
08-28-2011, 03:40 PM
Some of the diamond (read carbon) dissolves in the fragment of material that forms the spark. It is also possible that the grit may actually be shattered by contact and pieces fall away as diamond dust. Diamond is very hard but it also cleaves very easily.

Arthur.Marks
08-28-2011, 03:41 PM
Thank you for the clarification.

DICKEYBIRD
08-29-2011, 09:02 AM
Here's how I slowed down my 3450 rpm HF "carbide" grinder that I installed a 6" diamond wheel on t'other end. It's a 12v auto worm-drive power seat motor with a piece of rubber hose connecting it to the arbor shaft and a hose clamp mount.

It works pretty well for finishing although it's a bit too slow. I'm looking for a faster 12v motor or an 18-24v power supply to speed this one up.

http://i57.photobucket.com/albums/g227/DBAviation/DiamondSlowMotor.jpg

TheAndroid
08-29-2011, 11:06 AM
Where are you guys finding these cheap diamond wheels? I can't seem to coax that information out of Google.

rowbare
08-29-2011, 12:31 PM
Where are you guys finding these cheap diamond wheels? I can't seem to coax that information out of Google.
One source is: http://www.cdcotools.com/ Click on Machine Tool Toolings then Grinding Machine Tooling

bob

Evan
08-29-2011, 01:18 PM
Cheap diamond wheels are just that: Cheap. You get what you pay for. The grit concentration will be very low and they will wear much faster, cut hotter and slower than a good quality wheel. If you use the wheel much the best buy is the more expensive wheel as it will last much longer, more than enough to make up the difference in cost.

wierdscience
08-29-2011, 01:52 PM
One source is: http://www.cdcotools.com/ Click on Machine Tool Toolings then Grinding Machine Tooling

bob
That's where I get mine.100% concentration 1/8" depth they work great for the money.

PixMan
08-29-2011, 02:21 PM
FYI, from Norton Co. documents I have:

▼Diamond Concentration
❚ Concentration is the relative amount of diamond by carat weight in
a wheel. Concentrations can range from 25 to 200. Standard concentrations are equivalent in percentages of:
100 Concentration: 25% (diamond/CBN) volume of the abrasive section
75 Concentration: 18% (diamond/CBN) volume of the abrasive section
50 Concentration: 12.5% (diamond/CBN) volume of the abrasive section
❚ The higher the number, the more superabrasive there is in the wheel thus more cutting teeth and the wheel would be
harder acting.

I used to fall into the direct concentration reading trap. I now know it's quite a bit different, and now others do too.

The highest I've seen is a "150", so I think if we extrapolate the value correctly, that one would be a 37.5% actual diamond amount by concentration in volume of diamond to bonding agent. A "200" would still be only 50% by volume.

Tanto
08-29-2011, 03:32 PM
I have had a 4" diamond grinding wheel on my T&C grinder now about 4 years now and can't see any degrading from new. In fact I bought a spare wheel expecting this not to last.

Even if it only lasted a few months, at £10 a pop they are just consumables but this is not happening.

Yes don't buy a cheap diamond wheel otherwise you may have to replace it as often as John. I bought my cheap diamond wheel through ebay and based on the brilliant advice of the "experts" here I shall now destroy it immediately lest it last only "milliseconds" longer next time I grind HSS.

Evan
08-29-2011, 04:24 PM
Yes don't buy a cheap diamond wheel otherwise you may have to replace it as often as John. I bought my cheap diamond wheel through ebay and based on the brilliant advice of the "experts" here I shall now destroy it immediately lest it last only "milliseconds" longer next time I grind HSS.

Excellent advice to all and sundry. No doubt based on years of experience with abrasives.

A few of my wheels ( the larger ones aren't included):

http://ixian.ca/pics8/wheels11.jpg

Some examples of grinding (with the proper abrasives)

Regound flutes, CBN tool:
http://ixian.ca/pics9/tcgrind2.jpg

A form cutter made by creep feed grinding with a CBN wheel. A diamond wheel would be destroyed almost immediately in this application.

http://ixian.ca/pics9/bushing3.jpg

philbur
08-29-2011, 04:36 PM
For a thread that gave a lot of useful info you seem very skeptical. Having a quick scan back to see what the problem might be I see most of the crap is actually in your posts.

Evan's Norton link in post 6 pretty much provides the anchor for the rest of the discussion, or is Norton the expert you take issue with.

Phil:)


and based on the brilliant advice of the "experts" here I shall now destroy it immediately lest it last only "milliseconds" longer next time I grind HSS.

Evan
08-29-2011, 04:37 PM
To add to the correct advice previously given:



Diamond wheel on steels and CBN on carbides?

We get asked quite frequently if a diamond wheel can be used on steels and CBN on carbides. We do not recommend this as the wheel life will be greatly reduced and in some cases, the wheels may not even cut at all. A diamond wheel is specifically used for carbides, plastics and other synthetic materials. It will not grind steel well at all. CBN wheels should only be used on steels. There is a hybrid grit available that will grind both; However, it is a compromise in wheel life and grind-ability. But in cases where you must grind both materials at the same time, it can be a real time saver.

http://www.georgiagrindingwheel.com/grindingwheels_basics.htm#faq7

John Stevenson
08-29-2011, 05:12 PM
Sorry I have no axe to grind [ with or without diamond wheels :rolleyes: ], I'm only telling it as I find it.

Years ago I was paying nearly £100 a pop for 6" diamond wheels and I followed the instructions as I didn't want to wreck the wheels at that price.

Since the 'cheap' wheels have come about I decided that I had nothing to loose in keep swapping wheels on the grinder between different materials. Since then I have not noticed any difference in material stock removal but remember if you want large stock removal these wheels are not suitable.

ANY wheel suitable for large stock removal isn't good enough for finishing as well, that's why there are grades.

Evan has posted a picture of his stock of wheels which means nothing. Does he even use all of them ? I could post a picture of my stock of wheels which is approximately 10 times the size of Evans but most of these were bought in job lots and have never been used - most came off Tiffie :D

I do not disagree with what Norton says, after all they should know but all I am saying is the world doesn't end if you use a diamond wheel on a bit of HSS.

Remember I do this for a living and if a wheel only lasted me two months it would still be worth it in time saved in changing wheels over but the honest truth is that wheel I took the photo of has been on the machine since I bought it.
I have no reason to lie, I don't sell wheels or associated with them.

Tanto
08-29-2011, 06:27 PM
Evan's Norton link in post 6 pretty much provides the anchor for the rest of the discussion, or is Norton the expert you take issue with.

Phil:)

No, I think this basically sets the tone as to where the expertise lays


What affects the lifetime of any particular diamond wheel used on steel is a number of variables. The higher the grit concentration the better the wheel dissipates heat to the substrate. This is especially the case with resin bond wheels and the cheap wheels have low concentrations of maybe 50%. High quality wheels will be 75% to 100%.

At 100% the binder fills only the gaps between the grit which is packed as tightly as possible. This greatly improves conduction and these are the types of wheels used in industry.

And yes I think I'd put my faith in Norton rather than a posed photo of somebody's wife's collection of wheels thrown out by industrial users!


FYI, from Norton Co. documents I have:

▼Diamond Concentration
❚ Concentration is the relative amount of diamond by carat weight in
a wheel. Concentrations can range from 25 to 200. Standard concentrations are equivalent in percentages of:
100 Concentration: 25% (diamond/CBN) volume of the abrasive section
75 Concentration: 18% (diamond/CBN) volume of the abrasive section
50 Concentration: 12.5% (diamond/CBN) volume of the abrasive section
❚ The higher the number, the more superabrasive there is in the wheel thus more cutting teeth and the wheel would be
harder acting.


Like John, I have no axe to grind ... especially not on a diamond wheel :p The bottom line is that yes you can grind HSS on a diamond wheel and it's done constantly, in industry and in home shops. Yes coolant helps, just as it does with most machining operations, but I have a diamond wheel I sometimes mount on a bench grinder, and it certainly doesn't last "milliseconds" as one poster here claims. Both high speed and dry. The quality of the cheap Chinese wheels may not be up to the standard of top quality brands, but given that this is a home shop board, most likely more than adequate. For the cost of a tenner, stow the Google and give it a go.

lazlo
08-29-2011, 06:37 PM
Evan's Norton link in post 6 pretty much provides the anchor for the rest of the discussion, or is Norton the expert you take issue with.

http://ixian.ca/pics9/norton_tip.jpg

Would you agree that Norton's recommendation to use CBN to grind steel is not necessarily applicable to home-shop machinists?

Glendo advertising their diamond grinders as excellent for sharpening steel seems to contradict Norton's sweeping statement. Considering that Evan uses his (slowly rotating) diamond lap to sharpen HSS, I would think Evan agrees as well :)

I wouldn't be surprised if you'd wear the diamond off a wheel sharpening steel on a Baldor 500 (carbide grinder), which spins at 1800 RPM. Anyone want to try it? :D

Tanto
08-29-2011, 06:52 PM
Further to the above, just to cut through the considerable BS here regarding diamond concentration, here are a few links that will hopefully help. The notion that "more is always better" may seem logical to those who know no better, however is in fact complete crap. It will depend on what you're grinding, the speed at which you're grinding, and so on.

http://www.riegger-diamant.com/grundlagen/konzentration.php

http://www.diamondbladeselect.com/tips/diamond-tools-how-to-choose-diamond-concentration/

Please note the recommended uses on this last link

http://www.metlabsupply.com/supplies/index.php?main_page=index&cPath=5_43

Evan
08-29-2011, 07:08 PM
Evan has posted a picture of his stock of wheels which means nothing. Does he even use all of them ?

Yes, but not all at the same time.

Evan
08-29-2011, 07:10 PM
And yes I think I'd put my faith in Norton rather than a posed photo of somebody's wife's collection of wheels thrown out by industrial users!

Most of my wheels were new old stock when I got them. They didn't sell for various reasons including custom made wheels that were never picked up.



Further to the above, just to cut through the considerable BS here regarding diamond concentration, here are a few links that will hopefully help.

Read what I wrote. Concentration is like alcohol proof. 200 proof is 100% (actually 96%). As I said, 100% diamond concentration is the maximum amount of diamond that can be packed into the grit formulation. It isn't solid diamond, as I explained.

BTW, the random packing density of cubes is ~0.57. Not coincidentally a diamond concentration of "200" is equal to about 50% of space occupied diamond. That is equal to 100% diamond, the most that can be packed into a grit formulation with binder.

Tanto
08-29-2011, 07:58 PM
This is what you wrote Evan:


What affects the lifetime of any particular diamond wheel used on steel is a number of variables. The higher the grit concentration the better the wheel dissipates heat to the substrate. This is especially the case with resin bond wheels and the cheap wheels have low concentrations of maybe 50%. High quality wheels will be 75% to 100%.

At 100% the binder fills only the gaps between the grit which is packed as tightly as possible

That is wrong, particularly the part I highlighted. Most of the time I just let this sort of BS slide through, no point in making a Federal case out of something like this. However when I see other people getting sucked in by it I feel it's appropriate to correct it.

I have no interest in a tit-for-tat exchange with you Evan. I've seen the way you "discuss" things here. You want to claim that HSS can't be successfully sharpened on diamond wheels without them lasting "milliseconds" then you believe all you want. Arthur initially asked the question and hopefully that's now been answered. Meanwhile there are plenty of us out there, including at least 5 or 6 industry users I can think of off the top of my head who sharpen in house using diamond wheels without coolant. If I was running thousands of feet per day through machines then yes I would use the best wheel for the job (with coolant!), but for a home shop then a 10 quid wheel will do the job very well.

Paul Alciatore
08-29-2011, 08:27 PM
Diamond wheels cost what $20 a pop..... CBN costs probably $100 a pop... (they are bloody expensive compared to diamond)

I go with diamond...

Interesting thread. But what I want to know is where do you get these $20 diamond wheels? Home Depot? Ace hardware? Horror Freight? Are these the ones intended for cutting tile and bricks? 25% fill and less than 1/32" depth of coating? Probably 50 or 80 grit.

I mean seriously, don't real diamond wheels cost more like $75 to $100? Or do you guys know of a source that I don't?

J Tiers
08-29-2011, 08:33 PM
I have NO IDEA where this has gone....

Can't sharpen steel with diamond? ON WHAT PLANET?

I have had a Glendo for many years now.... it sharpens HSS VERY WELL.... yes, it also does an excellent job on carbide.... But no warning horns sound, and no flames erupt if I sharpen HSS.... and the wheel does not crumble away.

Lasts milliseconds? ON WHAT PLANET?

The Glendo I have has wheels that have been used by 3 users now, and are still going. The last user asked Glendo if he should get new ones, and they, after asking a couple questions, said he didn't need any new wheels... what he had (now mine) should be fine for years. They have been.

There is no POINT in discussing what Norton etc recommend, since it obviously applies to HIGH SPEED GRINDING, and not universally to all methods of grinding steel with diamond wheels.

There are multiple folks on here with slow speed wet wheel Glendo machines happily sharpening their HSS, with no intention of changing their activities. And the Glendo instructions don't seem to suggest we should.

Sheesh.................


Oh, yeah..... CDCO has cheap wheels? maybe cheapER, by a bit....... I just went and looked. They appeared to have 4 types, at either about $50 for smaller, or $70 for larger. Cheaper than some, but clearly not down at 10 UK pounds.

All appear to be 100 concentration, 150 grit

.RC.
08-29-2011, 08:42 PM
Interesting thread. But what I want to know is where do you get these $20 diamond wheels? Home Depot? Ace hardware? Horror Freight? Are these the ones intended for cutting tile and bricks? 25% fill and less than 1/32" depth of coating? Probably 50 or 80 grit.

I mean seriously, don't real diamond wheels cost more like $75 to $100? Or do you guys know of a source that I don't?

http://www.ctctools.biz/servlet/the-Cutting-Tools-cln-Diamond-Tools-cln-Grinding-Wheels/Categories

Tanto
08-29-2011, 09:16 PM
Paul, I bought mine through ebay, as I recall from Hong Kong. Just type in diamond grinding wheel or similar as a search.

As you can see this type is available in various abrasive sizes, this one for example is 600.

http://www.ebay.co.uk/itm/4-100mm-Diamond-coated-CONCAVE-grinding-wheel-GRIT-600-/150655277340?pt=UK_Home_Garden_PowerTools_SM&hash=item2313c1191c#ht_1087wt_907

John Stevenson
08-29-2011, 09:40 PM
Sheesh.................


Oh, yeah..... CDCO has cheap wheels? maybe cheapER, by a bit....... I just went and looked. They appeared to have 4 types, at either about $50 for smaller, or $70 for larger. Cheaper than some, but clearly not down at 10 UK pounds.

All appear to be 100 concentration, 150 grit

Sorry JT, just looked at current pricing and the wheels I use are now £14 but that includes tax which I can claim back.
They were £10 when I bought them.

http://www.arceurotrade.co.uk/Catalogue/Diamond-Tools/Diamond-Grinding-Wheels

oldtiffie
08-29-2011, 10:47 PM
Sorry I have no axe to grind [ with or without diamond wheels :rolleyes: ], I'm only telling it as I find it.

Years ago I was paying nearly £100 a pop for 6" diamond wheels and I followed the instructions as I didn't want to wreck the wheels at that price.

Since the 'cheap' wheels have come about I decided that I had nothing to loose in keep swapping wheels on the grinder between different materials. Since then I have not noticed any difference in material stock removal but remember if you want large stock removal these wheels are not suitable.

ANY wheel suitable for large stock removal isn't good enough for finishing as well, that's why there are grades.

Evan has posted a picture of his stock of wheels which means nothing. Does he even use all of them ? I could post a picture of my stock of wheels which is approximately 10 times the size of Evans but most of these were bought in job lots and have never been used - most came off Tiffie :D

I do not disagree with what Norton says, after all they should know but all I am saying is the world doesn't end if you use a diamond wheel on a bit of HSS.

Remember I do this for a living and if a wheel only lasted me two months it would still be worth it in time saved in changing wheels over but the honest truth is that wheel I took the photo of has been on the machine since I bought it.
I have no reason to lie, I don't sell wheels or associated with them.


I agree with John as given that wheels are only consumable items and that time is money, even a brief "off the cuff" or "gut feeling" (sort of) cost benefits analysis in a commercial environment may well show that given time to change wheels etc. that's it worth it to have a few multi-purpose ready use on hand to use as time and costs permit.

My wheels all have 1 1/4" (31.75mm) so they can be used on either a surface grinder and a tool and cutter grinder.

Diamond does not need any (re-dressing) - it may be useful to try it and to find out why - and it will pay for itself. The more so if you need several grades for speed of removal and finish.

Aluminum oxide and CBN wheels can be (free-) hand or diamond dressed/formed easily for those "special" jobs whereas diamond wheels usually cannot.

Having said that, there are no costs/profit or time considerations in some HSM. It may be that in some cases that costs are a consideration.

I often use wheels for surface work on my T&C grinder where the wheels are not on a balanced hub - they are just mounted on the plain 1 1/4" spindle nose. As I keep my wheels dressed, I can say that a T&C grinder is a very passable surface-grinder as regards accuracy and class of finish not-with-standing that the surface grinder is that little bit better.

No matter what I am grinding, I only take off only enough material to do the job required. Same applies to "finish". I rarely grind for "looks/appearance. To that end I use the coarsest wheel that I can and keep it dressed (al-ox and CBN) so that the wheel does not "glaze over" as that reduces cutting and caused "rubbing" and heat with potential micro-cracking or distortion.

If I can remove the bulk of material on the pedestal grinder, belt sander or the angle-grinder - that is what gets done before it goes onto a magnetic chuck on a surface or tool grinder.

lazlo
08-29-2011, 10:53 PM
Sorry JT, just looked at current pricing and the wheels I use are now £14 but that includes tax which I can claim back.
They were £10 when I bought them.

http://www.arceurotrade.co.uk/Catalogue/Diamond-Tools/Diamond-Grinding-Wheels

Um, how much diamond can those wheels possibly have for £10? :) I mean, they're mining, manufacturing and shipping a diamond wheel halfway across the world and still making profit on £10? :D

J Tiers
08-29-2011, 11:20 PM
JS, no problem.....

What's the exchange now? Seems like that 14 UK pounds might be around 20 bucks US or maybe a bit more? the dollar isn't doing great, but I didn't recall the pound being at a high value either. Could be wrong.



Um, how much diamond can those wheels possibly have for £10? :) I mean, they're mining, manufacturing and shipping a diamond wheel halfway across the world and still making profit on £10? :D

MINING?

betcha they MAKE the diamonds.......

In china you can still do anything for cheap..... out in the boons.... but it's getting more expensive in the major industrial areas.... Just like here.... small town wages are not the equal of city wages.

besides, nobody says the seller's source is HONEST...... they may be stealing the wheels, and selling them cheap wholesale to the HK contact.

How would you know? Do you care?

Tanto
08-29-2011, 11:53 PM
Um, how much diamond can those wheels possibly have for £10? :) I mean, they're mining, manufacturing and shipping a diamond wheel halfway across the world and still making profit on £10? :D

I agree. I expected they'd be manufactured diamond, but I'm just guessing. If you know the concentration you can establish just how much diamond is on the wheel. It's not a lot. Either way, like a lot of things coming out of China I just shake my head and wonder how they do it and still make good profits. However they do, and the important thing is that the wheels work pretty darn well.

Machtool
08-30-2011, 01:11 AM
Um, how much diamond can those wheels possibly have for £10?
Iím stuffing around with the idea of a home brew diamond wheel for sharpening scraper blades. I got a quote recently for a 7Ē dia, type 5 face wheel, to go on a Brobo toolroom grinder, our version of a Glendo. $741 bucks, so Iím not going there unless I really have too.
In looking around, we found this.

http://www.cutandslice.com.au/category21_1.htm

Iíve got 30 carats of #600 grit coming, a whole $36 bucks worth. For that sort of money, Iím going to try bonding it in a mix of Epoxy. And thatís out of Oz, you would do better out of Hong Kong. I thought it would be much more expensive.

Thatís a synthetic Russian diamond. 10 carats, looks to be about half a teaspoon to me.

Regards Phil.

philbur
08-30-2011, 04:32 AM
Hi Lazlo, I do agree that there is a need to interpret what Norton says in the context of a home shop environment:

ē Avoid steel when grinding with diamond wheels. Keep the amount of steel ground to an absolute minimum.

Not good for removing lots of steel. Which implies it can be used for tool and cutter grinding but is not suitable for a general purpose bench grinder or a surface grinder when grinding steel.

ē On brazed tools, use aluminium oxide wheel to back off the steel shank.

Not good for removing lots of steel.

ē A high lubricity grinding fluid should be used.

Keeping things cool will improve wheel life.

ē For some steels, an armoured (AMD) diamond wheel may prove most economical.

Some diamond wheels are better than others when grinding steel.

The clear implication for the HSM'er is that diamond can be used for a tool grinding steel but you should not use it for removing any amount of material. Keeping things cool (by what ever means is available to you) will improve wheel life. Some types of diamond wheels are better than others when grinding steel.

Anyone see anything controversial in that. Arn't we all saying the same thing while trying very hard to disagree.

Phil:)



Would you agree that Norton's recommendation to use CBN to grind steel is not necessarily applicable to home-shop machinists?

Glendo advertising their diamond grinders as excellent for sharpening steel seems to contradict Norton's sweeping statement. Considering that Evan uses his (slowly rotating) diamond lap to sharpen HSS, I would think Evan agrees as well :)

I wouldn't be surprised if you'd wear the diamond off a wheel sharpening steel on a Baldor 500 (carbide grinder), which spins at 1800 RPM. Anyone want to try it? :D

John Stevenson
08-30-2011, 04:42 AM
Um, how much diamond can those wheels possibly have for £10? :)

So far 4 - 5 years worth. :D
Not been to that factory but the boss of ARC has, massive factory making all sorts of diamond tooling for many trades.
I imagine the diamond is manufactured but can't say for certain but it's not a mom and pop business, turnover in in billions $$

They also do diamond lapping paste from #400 grit up to #25,000 grit, £3.50 for 5g syringe.

I also buy these [ well I have bought 2 and still on the first. ]

http://www.arceurotrade.co.uk/imagecache/c6efd5f3-a794-4161-9e88-ede48f7fae84_200x190.jpg

4" wheel to fit on an angle grinder so it runs at angle grinder speed which is fast.
I use these to rough brazed carbide tooling down prior to finishing on the other wheels. Finish is about as good as green grit and leaves a friable edge if looked at under a glass.

However stock rate removal is far faster than a green grit and less mess.

I have one of those cheap snipsaw attachment for an angle grinder and use the disk on this freehand.

It can take a 1/16" off a 3/4" shanked chipped brazed tip tool in 2 - 3 minutes. Had this a couple of years and not used the other side yet but in fairness it only gets used occasionally.
It also gets used to chop out big lumps of high speed when making stepped slotting tools and even at angle grinder speeds it's working OK.

I would never go back to green grit wheels, in fact I have given the small stock I had away.

mike4
08-30-2011, 05:06 AM
Sir john,
Thanks for your last posting ,it will save me some time , I had toyed with the idea of using an angle grinder with a similar wheel but thought that the grit size was too coarse.

Will get a couple and experiment with some chipped brazed tools.

Michael

Tanto
08-30-2011, 05:21 AM
Hi Lazlo, I do agree that there is a need to interpret what Norton says in the context of a home shop environment:

ē Avoid steel when grinding with diamond wheels. Keep the amount of steel ground to an absolute minimum.

Not good for removing lots of steel. Which implies it can be used for tool and cutter grinding but is not suitable for a general purpose bench grinder or a surface grinder when grinding steel.

ē On brazed tools, use aluminium oxide wheel to back off the steel shank.

Not good for removing lots of steel.

ē A high lubricity grinding fluid should be used.

Keeping things cool will improve wheel life.

ē For some steels, an armoured (AMD) diamond wheel may prove most economical.

Some diamond wheels are better than others when grinding steel.

The clear implication for the HSM'er is that diamond can be used for a tool grinding steel but you should not use it for removing any amount of material. Keeping things cool (by what ever means is available to you) will improve wheel life. Some types of diamond wheels are better than others when grinding steel.

Anyone see anything controversial in that. Arn't we all saying the same thing while trying very hard to disagree.

Phil:)

Yep, that's pretty much my interpretation and experience Phil. I believe due to the lower melting point mild steel does more damage than HSS, but I don't use diamond wheels that way so can't say from personal experience. HSS however is no problem at all.

Other Phil, are you making lapping plates for your scrapers? Why are you going to use epoxy as a bond? I doubt it will hold up well to any heat involved and is also relatively pliable.

lazlo
08-30-2011, 08:42 AM
MINING?

betcha they MAKE the diamonds.......

You need pure feedstocks for HPHT (high pressure high temperature) diamond manufacturing: graphite, iron-nickel catalysts, the diamond seeds...

Evan
08-30-2011, 08:42 AM
That is wrong, particularly the part I highlighted.

Wrong? Not according to the tables that show how much diamond is in a wheel.


Most of the time I just let this sort of BS slide through, no point in making a Federal case out of something like this. However when I see other people getting sucked in by it I feel it's appropriate to correct it.

It appears that most of the time you make a point of trying to pick an argument. Funny, you sound a lot like somebody else that hasn't been seen on the board lately.

----------------------------

Manufactured diamonds are widely used in cutting tools. PCD (poly crystalline diamond) is made from manufactured microscopic diamond crystals that are compacted under extreme pressure to form diamond inserts for cutting non ferrous materials. Diamond wheels are available made with PCD and are identified as such. They are much more expensive than wheels made with natural diamond. Natural diamond as used in most diamond wheels is a lot cheaper than man made diamond materials. They aren't made from gem quality diamonds, rather industrial quality diamonds. Prices are in the 1 to 3 dollar range per carat.

Note: There are uses for gem quality diamonds in machining applications. They are stronger as they are nearly pure carbon. I use gem quality diamonds to make engraving cutters. Industrial quality diamonds are perhaps only 96 percent carbon with many other elements present, particularly silicon.

lazlo
08-30-2011, 08:55 AM
I’m stuffing around with the idea of a home brew diamond wheel for sharpening scraper blades.

Phil, is this for your scraping class? I have an extra 300 mesh diamond wheel I can send you.


I’ve got 30 carats of #600 grit coming, a whole $36 bucks worth. For that sort of money

That’s a synthetic Russian diamond. 10 carats, looks to be about half a teaspoon to me.
...

Prices are in the 1 to 3 dollar range per carat.

Those sound like a lot more realistic prices. I paid about that price per tube of lapping compound.

For amusement purposes, amortize half a teaspoon of diamond for that £10 diamond wheel. I mean, I don't know how they can even be breaking even selling an aluminum disk for £10...

J Tiers
08-30-2011, 09:00 AM
I did not think there were many sources, and don't know of any in china. The way the chinese are about their sources, I'd have thought they would be all over indigenous sources, even manufacturing. If anyone can do it cheap and in quantity , it would be the chinese.

Russia, Congo, Australia and of course SA, plus some in India are the sources I know about, although I understand that Canada and Montana have some.

It was also my understanding that commercial manufacturing of abrasive diamonds was done, but it may be that it isn't currently profitable (at least outside china)..... Despite the fact that an abrasive quality diamond can be pretty nasty as far as what you would usually expect a diamond to be like.

Evan
08-30-2011, 09:05 AM
Prices are directly related to size. The coarser the grit the more expensive it is. It really begins to jump when you get into the sub 100 grit sizes.


although I understand that Canada and Montana have some.

Canada is a major producer of diamonds.

edit: A quick check of numbers show Canada is the third largest producer in the world with over 13 million carats per year. A high percentage of those are gem quality with total export value of over 2 billion dollars per year.

lazlo
08-30-2011, 09:43 AM
Prices are directly related to size. The coarser the grit the more expensive it is. It really begins to jump when you get into the sub 100 grit sizes.


Makes sense.

Since the thread has spun off into the weeds: a friend gave me an old World War II video showing the manufacturing of jeweled bearings. They would crush diamond feedstock, pour it into little whiskey glasses of mineral oil, and let it settle. The diamond powder that settled to the bottom was the coarsest mesh. Then they would decant the oil and let it settle again, and that was the next finest mesh. Repeat over and over, until you get the really fine mesh diamond that takes weeks (or months?) to settle.

Machtool
08-30-2011, 09:57 AM
Other Phil, are you making lapping plates for your scrapers? Why are you going to use epoxy as a bond? I doubt it will hold up well to any heat involved and is also relatively pliable.
I have lapping plates, all ready impregnated with diamond, one aluminium, one cast iron. They work better than expected for a final hone on carbide scraper blades. Iím not planning on heat. This isnít plunge grinding.

Why am I thinking about epoxy? Because thatís what I have here. I use an industrial Araldite called K-134. I use that for Turcite. In scraping that for cleanup of the over glue, I find thatís abrasive by itself. It blunts a blade, quicker than Turcite, and close to Cast Iron. It might be better full of diamond. I doubt its pliable, itís friggen tough to clean up.

Iím thinking of a grinding wheel that will be half way between a green silicon wheel for fashioning shape and a hone. For $36 bucks plus a piece of aluminium disc, Iíll try it. Nothing ventured, nothing gained.

I had / have a beautiful diamond wheel on this machine until I lent it to a bloke that picked it up by the steady rests. It put a lump in it and totally stuffed it.

Just for the record, when I took it off, it was Sharpy marked 1993. Iíve owned this machine since about 2002, I can post Pictures in the morning when I get back to work, Iíve done any amount of off- hand H.S.S grinding on it in that time. Iíve never noticed that it suffered during that time. I wasnít aware of the problem prior to the internet.


Phil, is this for your scraping class?
Yes, Iím scrubbing up all my gear, so its the best on display. Some of it is getting old, and Iím only 47. I have a few other things on order, but Iím trying this. 36 dollars in diamond beats a $741 dollar wheel. To be fair that was a German Winterthur wheel. Iím chasing a quote from Taiwanese Kinik, they should be a lot better. I sort of have rough grinding and finish honing covered, its that middle ground Iím trying to cover.

Its more about trying things for beginners to try. Especially down here. I can justify an expensive wheel, but Iím just trying options. Example:

http://www.cutandslice.com.au/category17_1.htm

Greg & I both have some of those discís coming to try. I doubt they will have any depth of diamond, but you just might end up with armís like pop-eye, if it was just for touching up a blade.

Regards Phil.

ckelloug
08-30-2011, 10:03 AM
If people are really interested in the subject, talk to the engineering guys at Continental Diamond Tooling http://www.cdtusa.net/ AFAIK, these are the folks that built the diamond drill bits for the NASA Mars Rovers.

I have had them make custom diamond saw blades for cutting some of my material samples of Silicon Carbide based epoxy granite composite on a 100 year old surface grinder. Apparently, there are a lot of variables in producing diamond blades and depending on how much steel you are planning to grind or cut, they will use a completely different blade design.

I started out with a diamond plated blade that didn't make the needed 5 cuts in one sample of the silicon carbide composite because I hadn't adequarely explained what I was trying to cut. Once I sent them a sample of the material, the next blade they made for me was a 10 inch slotted metal bonded diamond blade for about $300. They told me it could be used dry but would get better life with coolant even though the blanket catchall directions say that metal bonded blades should only be used with coolant. This one is still going strong after quite a bit of use dry.

Design of the blade is everything. While it is certainly cheaper to try a hoard of 10 dollar blades until you find one that doesn't self-destruct in your application, folks like Continental Diamond Tooling know what kind of diamond blade to use when you have to grind steel etc. but you will pay for that knowledge. HSM's probably get more satisfaction out of trying random stuff.

Machtool
08-30-2011, 10:37 AM
If people are really interested in the subject, talk to the engineering guys at Continental Diamond Tooling AFAIK, these are the folks that built the diamond drill bits for the NASA Mars Rovers.
That will be great to remember for the next time Iím making parts for the NASA Mars Rover.

While it is certainly cheaper to try a hoard of 10 dollar blades until you find one that doesn't self-destruct in your application,
Where have you seen one self Ėdestruct? That seems a bit far stretched.. John.S has given his first hand account of his 10 quid, becoming 14 quid wheels. I donít recall them blowing up on him.

Regards Phil.

John Stevenson
08-30-2011, 11:50 AM
The thing is believe it or not is that I'm not arguing with anyone, even Evan :)

I accept what people like Norton say, after all they should know.

I'm just relating how it works for me and no one wants to believe me.
I have put the links up where I buy these wheels from and just get told they can't make them for this when in fact those prices are retail including tax, if I asked what they were FOB Felixstowe I would get told but wouldn't post it here.

Everyone has to make a crust.

Please don't shoot the messenger :D

TGTool
08-30-2011, 12:59 PM
Human capacity for rationalization is, for all practical purposes, unlimited. People will believe what they want to believe and anything else is irrelevant.

It reminds me of a friend here in the US who told about driving a Jaguar Mk VII many years ago. He was stopped at a light with a car containing a couple older women to his left. The other car rolled down the window and asked Norman, "Is that a Rolls Royce?"

Norman took the pipe from his mouth and said, "No ma'am. It's a Jaguar."

The two ladies conferred and then asked him again, "Are you sure that's not a Rolls Royce?"

"Yes ma'am" my friend said.

After further consultation the woman turned to him a third time and said sternly, "Young man, that's a Rolls Royce and you know it!"

Does that sound like any of the dialogues here? :rolleyes:

Boucher
08-30-2011, 02:10 PM
Sir John

Thank you for posting this sort of information. I have been using the Diamond wheel on my tool grinder to do the finish operation on HSS tool bits. It has been a real improvement. Like grinding Carbide it is light and quick. Can't tell that the wheel has been degraded. Works great for me.

Again Thank you!

Chris S.
08-30-2011, 03:27 PM
I've spent many years participating on programming and electronics forums. I would sometimes chuckle when pondering which one of those two technical forums sported the highest number of egos. When I retired, semi, actually, I thought "Chris, it's time to let all that brain strain go and get back to more earthy endeavors". My Heavy10 has never been used, even though I've owned it for about 14 years. My Logan 920, that I converted to wood turning and I used to spend many hours on, has also sat dormant that long. Yup, "get some wood chips, metal chips and oil on those hands, and get together with some like minded folks".... That's what I said.

For those who are interested in their ratings on the ego chart... Nothing to fret about. You're right up there with the Programming and Electronics finalists! :eek:

BTW, I'm going to buy one of those $45.00 -$65.00 diamond wheels and sharpen HSS too! :p Hey, I just had a thought... Has anyone mentioned how well they handle carbon steel? :D

FYI: For those that are wondering why someone would desecrate a metal lathe by converting it to wood turning? All I can say is a Headstock, Tail stock, Bed and legs hardly constitute a metal lathe but it does make a great wood lathe and flat belts are a big bonus!

Chris

lazlo
08-30-2011, 04:53 PM
Despite all the kvetching, I think there's universal agreement that you can sharpen steel with diamond, especially if you keep the rpm's/heat under control :)

John Stevenson
08-30-2011, 05:17 PM
Robert, I don't think the revs are the problem as shown by using that diamond disc on the angle grinder which runs at ??rpm, dunno but it's fast.

Heat is another problem but that is easily managed by the simple expedient that if the tool gets too hot you drop it :rolleyes:

Tanto
08-30-2011, 06:58 PM
The thing is believe it or not is that I'm not arguing with anyone, even Evan :)

I accept what people like Norton say, after all they should know.

I'm just relating how it works for me and no one wants to believe me.
I have put the links up where I buy these wheels from and just get told they can't make them for this when in fact those prices are retail including tax, if I asked what they were FOB Felixstowe I would get told but wouldn't post it here.

Everyone has to make a crust.

Please don't shoot the messenger :D

That's something I will argue with ... in agreeance ;) Likewise John, I have no financial interest in this industry. I'm not here to sell diamond wheels to anyone, expensive or otherwise. Just trying to answer the gentleman's initial question. What I know is that for a home shop or modest use in industry, diamond wheels work perfectly well dry and at high RPM to grind HSS. I've used a new cutter grinder that comes standard with a 6" diamond wheel that spins at 5000 rpm. Dry. I personally spin my 4" wheel at almost 3000 rpm. Dry. So the resident egos can line up pictures of diamond wheels they've never used from their place back to China for all I care, like John, I'm actually using a 10 quid wheel to do precisely what the OP asked and it hasn't exploded in my face or lasted "milliseconds". No theory, no Google Searches, no idea of how they sell it for the price, no interest to pursue any of the above. That's just my personal experience.

Black_Moons
08-30-2011, 08:52 PM
I bet a lot of the "don't use diamonds on steel" comes from the industral sector where it economicaly does not make any sense, because its worth while to have a wheel for every job to make the best cost at it, and other wheels greatly outproformed it.. At a given cost.

Also, with great advancements in recent time in diamond manufacturing, and huge fall in price, Older text about 'Using diamonds does not make economical sense' may be completely incorrect, considering todays cost of diamond abrasives.

J Tiers
08-30-2011, 11:50 PM
Apparently most of us agree it is not a no-no......

I do sharpen steel with a diamond wheel (slow wet) JS uses faster dry grinding and it still works for him....

others as well....

Sounds like yes there can be reduced wheel life, but it also sounds like we here are not running into that.

I seem to stand corrected on the diamond sources, but that is a side issue as far as the OP.

philbur
08-31-2011, 08:32 AM
Yes, yes, your arguing in an empty room, everybody else has ageed and gone home. Do try to keep up.

The only ego still showing is yours.

Phil:)


That's something I will argue with ... in agreeance ;) Likewise John, I have no financial interest in this industry. I'm not here to sell diamond wheels to anyone, expensive or otherwise. Just trying to answer the gentleman's initial question. What I know is that for a home shop or modest use in industry, diamond wheels work perfectly well dry and at high RPM to grind HSS. I've used a new cutter grinder that comes standard with a 6" diamond wheel that spins at 5000 rpm. Dry. I personally spin my 4" wheel at almost 3000 rpm. Dry. So the resident egos can line up pictures of diamond wheels they've never used from their place back to China for all I care, like John, I'm actually using a 10 quid wheel to do precisely what the OP asked and it hasn't exploded in my face or lasted "milliseconds". No theory, no Google Searches, no idea of how they sell it for the price, no interest to pursue any of the above. That's just my personal experience.

ckelloug
08-31-2011, 09:23 AM
Machtool,

I was being a little facetious in my blows up comment. I really meant achieves reasonable durability. The CDT guys told me to dress my diamond wheels with a piece of low carbon steel. They consider cutting low carbon steel with diamonds to be equivalent to continuously dressing the wheel. Sure, it will work but it probably won't lead to maximum life. What the loss of life is, I don't know.

I have not sharpened steel on my wheels, my comment was mainly to say that I have seen two different diamond wheels behave quite differently on the same task where one got fine life and one stopped cutting effectively after a few minutes. The CDT guys ask how much steel will be cut when you ask for a custom wheel and will change designs if you give them a number over a few percent.

I did not pick these guys because of their Mars Rover Drills, I picked them because they could deliver the odd arbor hole size on a 10 inch wheel for my surface grinder.

KEJR
09-01-2011, 08:10 PM
After reading these posts I stumbled upon a source for these cutter grinder cup wheels on ebay:

http://www.ebay.com/itm/Diamond-Grinding-Wheel-Cup-Grit-Cutter-Grinder-Tool-New-/130571057720?pt=LH_DefaultDomain_0&hash=item1e66a43a38

I'm thinking of adapting one of these onto one of my grinders and adding a tilt table. Any reason not to do this? I'd like to be able to touch up my brazed carbide and fine finish my HSS.

KEJR

Chris S.
09-01-2011, 08:49 PM
Did you check out the "ECONOMY SHIPPING" @ $19.95? It's also lacking the the grit % that's been discussed throughout this thread

Chris

tdmidget
09-01-2011, 09:46 PM
Machtool,

I was being a little facetious in my blows up comment. I really meant achieves reasonable durability. The CDT guys told me to dress my diamond wheels with a piece of low carbon steel. They consider cutting low carbon steel with diamonds to be equivalent to continuously dressing the wheel. Sure, it will work but it probably won't lead to maximum life. What the loss of life is, I don't know.

I have not sharpened steel on my wheels, my comment was mainly to say that I have seen two different diamond wheels behave quite differently on the same task where one got fine life and one stopped cutting effectively after a few minutes. The CDT guys ask how much steel will be cut when you ask for a custom wheel and will change designs if you give them a number over a few percent.

I did not pick these guys because of their Mars Rover Drills, I picked them because they could deliver the odd arbor hole size on a 10 inch wheel for my surface grinder.


Oh please! Continental Diamond Tool is a "women" owned company? They use a "phonelic" resin? Can't you see the chink here?
http://www.keentool.com/NewsView.asp?id=210
I know someone at the U of AZ, who built the Mars rovers. Shall I check on who built the tools or do you need more egg on your face? 2 to 1 your "diamond" wheels aren't the real thing.