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Boucher
01-13-2010, 10:24 AM
I normally defer to people that obviously have much more experience than I do. I don't remember who posted it but there is a very good and informative thread with detailed instructions on grinding HSS tool bits. The concept presented that I seriously Question re Using belt sanders. It is stated that the pressure of the bit against the belt causes sort of a slack bulge just above the cutting edge rounding it and therefore ruining it. To the best of my limited knowledge I just don't think that is True. I would like to know what others think on this subject.

This kind of reminds me of that old Quip," Who are you going to believe Me or your lying eyes."

Doozer
01-13-2010, 10:36 AM
Get some of those diamond lap hand held files.
The ones with different colored handles for grit size.
They are real nice for final edge prep when sharpening toolbits.

http://www.sussextools.co.uk/images/products/398.jpg

--Doozer

Carld
01-13-2010, 10:42 AM
I don't know why but a belt sander won't leave as sharp an edge as a grinder wheel does. I use a belt sander to rough the cutters and drill bits to size/shape sometimes but I finish on a grinder wheel and sometimes hand dress it.

Maybe he saw the same thing I have. It works better when sharpening a drill real fast but you still don't get as sharp an edge as a stone gives.

Lew Hartswick
01-13-2010, 10:43 AM
I would say "it depends". :-) In particular on the SHAPE of the
backing of the belt. If the the backing is a flat and the belt is "not
quite" dead tight against it you will get rounding of theedge.
But if you use the place where the belt goes over the large round
wheel (just like a wheel on a grinder) it will produce a surface
just as the wheel will but will be a cooler cut.
...lew...

edit. It depends on the grit used to, usually a belt grinder/sander
has a lot coarser grit than yout typ. grinder used for bit sharpening.
..l..

JCHannum
01-13-2010, 10:53 AM
Hold the bit upside down if that is a concern. That will put the dull side on the bottom.

I don't use the belt, but I do use the disc on my sander to touch up HSS tools.

Black_Moons
01-13-2010, 11:04 AM
iv used verious sanders. and holding the bit 'upside down' is good advice as I find on sanders the bit sometimes 'grabs' and tilts slightly in your hand before snaping back into place, THAT will round the cutting edge for sure.
Finishing with a diamond lap is a good tip even for wheel ground tools. a fine smooth finish on top will likey help reduce material welding to your tip as well
Also all you need is a few licks with a lap to resharpen if you don't let it get too dull. (laping the cutting edge becomes easyest with a hollow grind, this is the 'advantage' of a hollow grind as you only lap the cutting edge, not the whole face)

Diamond coated files are also good for tweaking chip breaker grooves (I usally start the grove by gnashing with a 1~4.5" cutoff disk, and finish with a very small round diamond coated file), and laps/coated files can be used to tweak HSS bits geometry with extream precision (ie getting the last degree or two on your HSS threading bit, using the fishtail gage as a visual refrence, you can adjust the angle by applying more pressure to one side of the file or the other while fileing the sides.

lazlo
01-13-2010, 12:21 PM
I use a 1" Zirconia belt one an old Delta/Rockwell belt sander/grinder to touch-up HSS, and it works great.

Seriously, it doesn't have to be perfect -- when I buy lots of HSS on Ebay, some of the hand-ground tools that come out of Pro shops are astonishingly bad, and they're putting dinner on the table with them.

Machinist-Guide
01-13-2010, 01:04 PM
I use the belt sander from time to time I think the most importand thing is to not get the bit too hot. Your cutting edge will heat up faster on the belt sander. Dip it in water often. Don't wait till it gets hot to dip it. Dip when you first feel it getting warm. If you let it get hot it will anneal the cutting edge.

I am posting a link to a retired machine shop teacher that has made 3 videos on sharping lathe bits. He has done a really good job with his video. He uses large wooden blocks as a tool bit model to show all the rake and clearance angles

Here is the link

Tool Bit Sharpening Video (http://www.machinist-guide.com/lathe-tool-bits.html)

recoilless
01-13-2010, 02:08 PM
This was touched on in one of Harold V.'s posts over on Chaski's site.

http://www.chaski.org/homemachinist/viewtopic.php?t=75985

Peter N
01-13-2010, 02:18 PM
I use the belt sander from time to time I think the most importand thing is to not get the bit too hot. Your cutting edge will heat up faster on the belt sander. Dip it in water often. Don't wait till it gets hot to dip it. Dip when you first feel it getting warm. If you let it get hot it will anneal the cutting edge.


????
High Speed Steel is chosen primarily for its property to retain full hardness even at red heat, so I doubt that a belt sander will anneal the edge - except at maybe a microscopic level.
Dipping is a good idea though, as it saves your fingers getting burnt.

Peter

Boucher
01-15-2010, 04:00 PM
Quote: It depends on the grit used to, usually a belt grinder/sander
has a lot coarser grit than yout typ. grinder used for bit sharpening.

No No No..... That is the beauty of a belt sander you can change grit size in 30 seconds.

The belt sander is 5 times faster.... and cooler cutting than the grinding wheel.

As for turning it upside down, I normally set the angle of the table at 7° for the relief angle. I can't quite visualize the grinding with the table tilt in the oposite direction but you can bet I will check it out. If it works that is a great idea.

I really appreciate this site. My brain doesn't work like it should, or like it used to, but the inputs here help me. Thank you!

SVS
01-15-2010, 05:01 PM
I have a 30's era Oliver drill grinder. The manual goes on at length concerning intermitent cooling of HSS during grinding-essentially stating "grind dry or under flood....dunking causes stress cracks."

Since reading that I've gone to wearing gloves or doing something else while the bit cools enough to hold. Nothing scientific, but I think my results are improved.

Same school of coolant theory as applies to turning and milling with carbide.

Scott

vpt
01-15-2010, 05:06 PM
When I was in school I was told to always grind with the tip or sharp end up. For tig welding they tell you to grind your tungsten with the tip facing up on the wheel so the crap and the (slag) will be pushed back away from the tip.

As for the cutting edge of say a knife, lawn mower blade, HSS lathe tool, I was told you will get the sharpest cleanest edge grinding with the sharp edge/tip facing up on the grinder. Maybe a belt sander is different but a stone wheel will always leave a bit of slag on the bottom edge of a grind that will leave a dull edge when cleaned.

Boucher
01-15-2010, 05:42 PM
vpt: You are right the top edge up is the correct orientation to grind the tool. Also when dressing the edge the stone is supposed to move over the it in the same direction that the chip does.

Scott: I know that carbide is sensitive to thermal stress/cracking. I don't think that HSS is. I don't know if this is related to improvements that have been made in recent years. In any case I keep a paint can of water handy for cooling.
Again it is surprising how much cooler the bit stays when grinding with the belt sander.

I started using some Norizon belts recently and they are way better than the old ones that I have been using.

oldtiffie
01-15-2010, 08:52 PM
This is my disc and belt sander - on my pedestal grinder:

http://i200.photobucket.com/albums/aa294/oldtiffie/Belt_sander/Belt_sander1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Belt_sander/Belt_sander2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Belt_sander/Belt_sander3.jpg

I never use the guides on the disc for grinding tool bits - although it works well. I use it occasionally for "other stuff" as I free-hand grind most of my HSS turning tools.

I NEVER have the sander going from the top (cutting edge) to the bottom of the tool-bit on the sanders - I use that "top to bottom" technique on the "emery" wheel on the pedestal grinder. If the tools need a lot off they get "the treatment" with the angle grinder and a bucket of water. THEN its off to either or both the "emery wheel" and/or sanders - and bucket of water.

Reason is that the belt is flexible (emery wheel is not) and belt-sanding from the top down does cause a slight "rise" on the face edge neares the cutting edge where the belt first contacts the face being sanded. Going from "bottom up" leaves a fine sharp feather edge on the "top" of the tool which is soon eliminate as part of the follow-up hand-honing.

(Hand hones are mainly "diamond laps/sticks" - but are sometimes "oil stones" - it depends on the edges being sharpened).

The belt sander has a flat support plate under its "flat" section - which I don't use much either. I do all my work on the front (curved surface) of the emery wheel and the belt sander.

The "wheel" under the front of the belt sander is "vented" and "ribbed" to pass air through which keeps the belt and tool much cooler than working on the face of the emery wheel.

I prefer a "hollow-ground" face to all my tools as I hand-hone them - I need only the top and bottom of the curves - not the whole face as would be the case if the face were flat. So re-sharpening with a hand-hone is quick and easy - on the lathe or off it.

I have range of belts (36" x 2") "grit" sizes and types as spares and for a range of uses and applications.

Here are some of the diamond grit hand hones:
http://i200.photobucket.com/albums/aa294/oldtiffie/Precision_grinding/Abrasives1.jpg

wdtom
01-15-2010, 09:17 PM
I have a small (4" dia.) 6 jaw lathe chuck That a friend found at a yard sale. It seems to be well made and finished however if I tighten the screws that hold the reverseable jaws on it tightens up the jaws so they can't be moved. On the back of the chuck there are 3 small screws near the center that hold the back of the chuck on. The back is the scroll and the rim is knurlled to grip it and has 6 approx. 7/32 dia. holes in it that you could stick a pin in for leverage in adjusting. On the back of the chuck it says "ZW Swiss made" and also "Zweifal AG CH 8620 Wetzlkan Typ-df" The chuck would mount on a 1" shaft with 3 approx. #8 capscrews.The face of the chuck is counterbored for the capscrews under 3 of the 6 jaws. The hole through the center is approx. 3/8" . You can't shim the jaws adjust clearance as the back of the jaw where the shim would go is concave. Does anyone know anything about this chcuk? I am leaning toward putting the screws in with loctite and mounting it on a 1" shaft/arbor to use for small delicate work. Thanks for any information anyone might be able to give me.

Tom

wdtom
01-15-2010, 09:17 PM
I have a small (4" dia.) 6 jaw lathe chuck That a friend found at a yard sale. It seems to be well made and finished however if I tighten the screws that hold the reverseable jaws on it tightens up the jaws so they can't be moved. On the back of the chuck there are 3 small screws near the center that hold the back of the chuck on. The back is the scroll and the rim is knurlled to grip it and has 6 approx. 7/32 dia. holes in it that you could stick a pin in for leverage in adjusting. On the back of the chuck it says "ZW Swiss made" and also "Zweifal AG CH 8620 Wetzlkan Typ-df" The chuck would mount on a 1" shaft with 3 approx. #8 capscrews.The face of the chuck is counterbored for the capscrews under 3 of the 6 jaws. The hole through the center is approx. 3/8" . You can't shim the jaws adjust clearance as the back of the jaw where the shim would go is concave. Does anyone know anything about this chcuk? I am leaning toward putting the screws in with loctite and mounting it on a 1" shaft/arbor to use for small delicate work. Thanks for any information anyone might be able to give me.

Tom

Black_Moons
01-15-2010, 09:31 PM
wdtom: make a new thread, this is not the place for your double posted question.
Nifty sander addon
Peter Neill: I highly doubt that HSS retains its strength at RED HOT tempatures, Anneling your blank would be very bad. (And yes, pushing it into a glazed over wheel can get your blank glowing red hot and annel it)

Most HSS bits are actualy ground freehand, so its not angleing your table upside down but just how you hold and present it to the wheel.

Peter N
01-16-2010, 02:34 AM
Peter Neill: I highly doubt that HSS retains its strength at RED HOT tempatures, Anneling your blank would be very bad. (And yes, pushing it into a glazed over wheel can get your blank glowing red hot and annel it)
.

Back to school for you then Black Moons :D (do you have a name btw?)
But by all means don't just take my work for it - do a little research of your own - but yes, High Speed Steel WILL retain it's hardness at a dull red heat.

Peter

Machinist-Guide
01-16-2010, 03:28 AM
About 30 years ago at the age of 19 or 20 I was working in a small tool & die shop with my gray headed old geezer journeyman. We were both running the same simple parts on pretty much the same model lathe. My journeyman shaped my bit and set my speed and feed, because I had no clue how to do it myself. After the first day I noticed he ran about 20 parts more then I did. The second day I watched every move he made trying to see why he was running more parts then me. At the start of the shift on the 3rd day I ask him what he was doing that I wasn’t. His reply was. I will show you around first break” Well a few minutes before first break I stopped to sharpen my bit. My journeyman walks up to me and says “Son how many times have you seen me stop to sharpen my tool sense we started running this job. After I thought about it my reply was.” I haven’t seen you sharpen your tool” With a big grin on his face he told me “That’s why I run more parts then you, I am making chips on the lathe while you are making sparks on the grinder. That’s when he explained to me if you get your tool hot enough to make the water sizzle when you dip it you have got it to hot. Dip your tool before it gets hot.
Now today I am the gray headed old geezer making chips while I watch the school boys make sparks.

Just because a tool is hard don't mean it's a good tool:)

Peter N
01-16-2010, 05:02 AM
About 30 years ago at the age of 19 or 20 I was working in a small tool & die shop with my gray headed old geezer journeyman. We were both running the same simple parts on pretty much the same model lathe. My journeyman shaped my bit and set my speed and feed, because I had no clue how to do it myself. After the first day I noticed he ran about 20 parts more then I did. The second day I watched every move he made trying to see why he was running more parts then me. At the start of the shift on the 3rd day I ask him what he was doing that I wasn’t. His reply was. I will show you around first break” Well a few minutes before first break I stopped to sharpen my bit. My journeyman walks up to me and says “Son how many times have you seen me stop to sharpen my tool sense we started running this job. After I thought about it my reply was.” I haven’t seen you sharpen your tool” With a big grin on his face he told me “That’s why I run more parts then you, I am making chips on the lathe while you are making sparks on the grinder. That’s when he explained to me if you get your tool hot enough to make the water sizzle when you dip it you have got it to hot. Dip your tool before it gets hot.
Now today I am the gray headed old geezer making chips while I watch the school boys make sparks.

Just because a tool is hard don't mean it's a good tool:)


Machinist-Guide, try not to take this personally as I don’t have a problem with you per se, but little anecdotal stories like this are fine from someone like Forrest Addy as what he says can often be verified time and time again.
But I have a problem when someone named “Machinist–Guide” and whose profile says he is an old-school Toolmaker gives out information on this board that is just plain wrong – as in the case of annealing HSS on a belt sander or HSS being too hot because it ‘makes the water sizzle’. Whilst this is possibly true of carbon steel cutters it is entirely wrong and misleading for HSS, and the low temperature of around 100deg C or less required to ‘make water sizzle’ will have no effect on HSS. Personally I can’t hold on to it once it gets to even 60deg C, which is nowhere near hot enough to affect anything. Even if you get it to change colour to Blue it will still be hard.

HSS retains its hardness and cutting edge at Red Heat – FACT. Let me quote from one of your own US cutting tool suppliers:

“Tungsten Note: Generally speaking, a cutting tool made of high speed steel containing the element tungsten will possess the very desirable property of "red-hardness". This enables tools to cut at a dull red heat (up to 1000° F) without loss of hardness or rapid dulling of cutting edge. Cobalt high speed steel will exhibit even greater red-hardness and wear resistance.”

http://www.icscuttingtools.com/Tooldata.htm

And as for the nice little story above, perhaps it did happen, but I’m sure you won’t mind me pointing out that it’s full of inconsistencies.

- You intimate that your Journeyman produced more parts than you because you ground your cutter too hot, but just prior to that you state that he was the one who ground your tool bit and set your speeds and feeds. So he ground it wrong then did he?
- You say that he had to do this “because I had no clue how to do it myself”, so perhaps that gives you a clue as to why he produced more than you?
-And unless ‘small tool & die shops’ are vastly different on your side of the Pond from mine, then they don’t run production parts , which is what your story hints at ( 20 parts more than me/3rd day of same job/change of shift on the job). Over here Tool & Die shops make Mould & Press Tools which are 99% one-off jobs, although they may be multi-stage and multi-cavity, and as such require multiple parts. But never usually enough to have several people working shifts making the same parts.

We are about the same age,You and I, and I did qualify as a Toolmaker some 30 years ago, and posted all my papers on here in the past to prove it. I’ve been in the same industry ever since from apprentice to technical director, and have my own Injection Moulding and Toolmaking business, although the Toolroom is run entirely by my partner. Machining for me is just a hobby with the occasional R&D and prototype work for some of our clients, but I can safely say that I know a little bit, although others know a lot more than me, and I try and help out with information when I can.
But if we’re going to be providing a ‘Guide’ and information – particularly for those new to the hobby – let’s try and make sure they get the right information eh?

And I do agree with the last statement, just because a tool is hard doesn’t mean it’s a good tool. That bit is spot on.

Peter

Machinist-Guide
01-16-2010, 05:59 AM
Tool Shops on this side of the pond make what ever the customer wants.
If they want a button we make it. If they want 1000 buttons we make'em.

If you want to grind your tools hot go for it.
I think I will keep mine as cool as possible.

And as far as all you guys here to learn. Try this. Get 2 HSS tool bits grind one and keep it as cool as possible . Grind the other one till it gets red on the cutting edge. Then go use them and decide for yourself which one last longer.

Then get you a HSS drill bit crank up the RPM till it turns red and see how many chips you make with it.
And when I say HSS I am not talking about Tungston or Cobalt

“Tungsten Note: Generally speaking, a cutting tool made of high speed steel containing the element tungsten will possess the very desirable property of "red-hardness". This enables tools to cut at a dull red heat (up to 1000° F) without loss of hardness or rapid dulling of cutting edge. Cobalt high speed steel will exhibit even greater red-hardness and wear resistance.”


Tungston? Cobalt? I thought we were talking about HSS

These are not plan old HSS they are special and cost more.

Peter N
01-16-2010, 06:15 AM
Tool Shops on this side of the pond make what ever the customer wants.
If they want a button we make it. If they want 1000 buttons we make'em.

If you want to grind your tools hot go for it.
I think I will keep mine as cool as possible.

And as far as all you guys here to learn. Try this. Get 2 HSS tool bits grind one and keep it as cool as possible . Grind the other one till it gets red on the cutting edge. Then go use them and decide for yourself which one last longer.

Then get you a HSS drill bit crank up the RPM till it turns red and see how many chips you make with it.
And when I say HSS I am not talking about Tungston or Cobalt

“Tungsten Note: Generally speaking, a cutting tool made of high speed steel containing the element tungsten will possess the very desirable property of "red-hardness". This enables tools to cut at a dull red heat (up to 1000° F) without loss of hardness or rapid dulling of cutting edge. Cobalt high speed steel will exhibit even greater red-hardness and wear resistance.”


Tungston? Cobalt? I thought we were talking about HSS

These are not plan old HSS they are special and cost more.

All HSS has Tungsten in it, and the second most commonly used HSS (M42) has Cobalt in it, as do most of the other grades with the exception of M2 so we're talking plain common-or-garden HSS - nothing special at all.


Peter

Edited Again: Now I'm back from Town, I re-read my post and decided that it was overly rude - so I will apologise for that and have edited those remarks out. We'll just have to agree to disagree.

Machinist-Guide
01-16-2010, 06:30 AM
My credentials as of November 13 2009. 20 years working for the world’s largest automotive supplier as a toolmaker.

www.magna.com (http://www.magna.com)

12 years prior to that I worked in various machine and tool shops here in Oak Ridge Tennessee.

John Stevenson
01-16-2010, 06:42 AM
I can remember as an apprentice being shown at college a HSS steel tool with a torch playing on it to get it dull red and still cutting.
The same was done with carbon steel, Stellite and a one of the propitiary Mushett <sp> steel brands.

Only the carbon steel didn't survive.

.

Machinist-Guide
01-16-2010, 07:16 AM
Ok maybe I have been misunderstand. Let me try to say this another way I agree you can get HSS hot and it will cut. I have welded HSS to CRS to make boring bars before. It will cut after you get it hot but your cutting edge will last longer if you keep it cool.
I think anyone on this forum would agree that if you get a end mill hot it will get dull faster then it would if you keep it cool.
What are end mills made of?

I agree HSS will stay hard when it gets red hot but when it cools it becomes "spotty" and it's no longer as high quility tool as it was before it overheated.

As the song says "That's my story and I'm sticking to it"

The cooler you keep your tool when sharpening it or using it the better off you are.

Tony Pratt
01-16-2010, 07:33 AM
Mr Machinist Guide, you beat me to it! Commonsense dictates you keep your cutting tools cool when regrinding or in use, I think we all have overheated milling cutters in the past and they never seem the same. I don't believe any decent machinist would intentionally run a cutting tool at red heat, it can't be good for the job or the tool whatever the jargon says. Peter, you are spot on with your HSS facts[ I couldn't spell metallurgy ]

Tony Pratt
39 years cutting metal

luthor
01-16-2010, 07:43 AM
Mr Machinist Guide, you beat me to it! Commonsense dictates you keep your cutting tools cool when regrinding or in use, I think we all have overheated milling cutters in the past and they never seem the same. I don't believe any decent machinist would intentionally run a cutting tool at red heat, it can't be good for the job or the tool whatever the jargon says. Peter, you are spot on with your HSS facts[ I couldn't spell metallurgy ]

Tony Pratt
39 years cutting metal

There is a big difference between overheating a HSS cutting tool during actual metal cutting and when grinding.

Machinist-Guide
01-16-2010, 07:50 AM
Someone understands what I was trying to say.
Some guy ask about sharpening there bit on a belt sander. All I said was to keep it cool and the attacks begin.

Tony Pratt
01-16-2010, 07:51 AM
How so ? Please explain.

Tony Pratt
01-16-2010, 08:00 AM
Hi Luthor, please ignore my over hasty reply, there is indeed a big difference ! In both cases heat is generated by friction? in one, the grinding wheel cuts the tool in the resharpening process and in the other case the tool heats up whilst it is actually cutting metal under load. Is that what you meant?

Tony

Your Old Dog
01-16-2010, 08:09 AM
..........................

Since reading that I've gone to wearing gloves or doing something else while the bit cools enough to hold. Nothing scientific, but I think my results are improved...................................
Scott

I use my bare fingers. When I feel even the slightest warmth I dunk in water. The rule of thumb is to spend as much time on the water as you do on the wheel. I've never had a problem doing it that way.

Keep in mind, knifemakers using the stock removal method only use belt grinders. They believe the unforgiving charastics of a stone wheel are what actually cause the problems.

Machinist-Guide
01-16-2010, 08:22 AM
I have a 30's era Oliver drill grinder. The manual goes on at length concerning intermitent cooling of HSS during grinding-essentially stating "grind dry or under flood....dunking causes stress cracks."

Since reading that I've gone to wearing gloves or doing something else while the bit cools enough to hold. Nothing scientific, but I think my results are improved.

Same school of coolant theory as applies to turning and milling with carbide.

Scott

You are correct. Thats why I say keep it cool dip it before it gets hot.

Machinist-Guide
01-16-2010, 08:25 AM
I use my bare fingers. When I feel even the slightest warmth I dunk in water. The rule of thumb is to spend as much time on the water as you do on the wheel. I've never had a problem doing it that way.



I agree dip it before it gets hot.

Ed P
01-16-2010, 08:33 AM
The following is taken from "Machine Shop Trade Secrets" by James Harvey.
"You may have heard that while grinding HSS you shouldn't let it get too hot or it will lose its hardness. I've always ground HSS aggressively and never noticed a reduction in its hardness.
Just to remove any doubt, I did a test one day. I took an unaltered piece of HSS and checked it for hardness. It measured about 65 RC which is about what you'd expect. Then I went to our old worn out pedestal grinder and abused the heck out of that piece of steel. I got it red hot as I held it mercilessly against our old glazed over grinding wheel. Then without dipping it in water, I checked the hardness of the face I had just ground. It turned out to be as hard as it was originally."

Ed P

Ed P
01-16-2010, 08:46 AM
And the following is taken from "Design and Use of Cutting Tools" by Leo St. Clair.
"One must grind tools in such a way as to produce as little heat as possible. The sudden overheating of the tool material while grinding causes a rapid expansion of the tool material surface that is next to the wheel. The tool material under the overheated surface is still cool and consequently not expanded.
The difference in expansion between the surface layer and the inner portion of the tool causes the tool material to check or crack. These grinding cracks weaken the edge area and cause it to break down rapidly through crumbling and chipping. Such cracks are often so fine that they cannot be seen by the naked eye."

Ed P

lazlo
01-16-2010, 09:40 AM
And the following is taken from "Design and Use of Cutting Tools" by Leo St. Clair.
"One must grind tools in such a way as to produce as little heat as possible.
These grinding cracks weaken the edge area and cause it to break down rapidly through crumbling and chipping. Such cracks are often so fine that they cannot be seen by the naked eye."

That's the singular quote (from Leo St. Clair's book) that caused the great "Don't Dip" war on rec.crafts.metalworking in the late 90's. :p

Many folks pointed out that just about every machinist book that's ever been written, as well as the instructions from the foundry, instruct you to dip to keep the toolbit finger warm (cool enough to hold), and not coincidentally all grinding machines have a dip pot :)

Ian B
01-16-2010, 10:37 AM
When grinding a tough bit of steel,
Mix a little discretion with zeal.
Keep the work on the move,
Or you'll grind a deep groove
In that long-suffering emery wheel...

Remembered that from a Model Engineering mag, years ago.

I'm also one of the dipalot tribe. However, I remember taking a 6" length of 5mm diameter Chinese ground HSS rod, heating the end to orange / yellow and trying to bend it - couldn't believe how hard it still was to bend. Seems the stuff doesn't lose its hardness easily.

Ian

vpt
01-16-2010, 11:19 AM
I am turning some steel right now in the lathe. I was having problems with my original piece getting work hardened time and time again when I was just grinding my cutter and throwing it in the tool holder. Sometimes without even getting a full rotation the bit would dull out and rub. Well last night I ground a new sharp on the bit and dunked it in water to keep it cool before throwing it in the tool post. That single grind was able to face three sides of the same piece of steel that was giving me trouble before without a problem and a much better finish on the work. I will always be keeping my bits cool from now on when sharpening! I do remember after doing this that in school they had a water can on the front of the grinder and the instructor told us make sure you keep the bits cool by dunking them. This was 15 years ago so I forgot most of what I was taught but it is coming back to me as I go along.

Boucher
01-16-2010, 12:06 PM
I initally grind my HSS bits freehand so I am holding them with my fingers. I cool them as soon as I feel warm on the back side. When I say freehand, I have the bit setting on the table tilted at 7°. I mark the line that I am going to grind to with a fine tip marker. The belt sander (which was the original point of this thread) cuts much faster and cooler than grinding on a stone.

When I touch up a bit I leave it in the Quick change tool holder set that on the table of the Baldor type tool grinder and use the protractor tool to guide it at the correct orientation. This is just a very quick brush on the fine stone to touch up the edge. No need to quinch it. Then I stone it with a fine stone.

airsmith282
01-16-2010, 12:22 PM
i use 100 gritt belt and disc on the sanders no problems there at all and i have used the grinder as well only the fine wheel i never use hte course wheel and still there about the same really you can get a better releaf or rake angle on the grinder but both work and i use both ways and have had no problems either way ,.,

make sure to have water on hand to keep cooling the bit down other wise ya youll mess it up and make it really weak...

Black_Moons
01-16-2010, 12:26 PM
Awsome arguement I started here. :P Good thing im not the only one misinformed or id feel foolish.

Did'nt think it would retain strength so hot.. I kinda allways thought when you started causing your HSS to change color (straw color, blue, etc) it was anneling the metal. (Sure I read that here somewhere.. that letting its color change was bad) And iv heard HSS is very hard to heat treat back to hardness so trying to heat treat again after grinding is out for HSM.



I'm also one of the dipalot tribe. However, I remember taking a 6" length of 5mm diameter Chinese ground HSS rod, heating the end to orange / yellow and trying to bend it - couldn't believe how hard it still was to bend. Seems the stuff doesn't lose its hardness easily.
Ian

Woah. Bending HSS? I never even considered this
Is this how they make those bent HSS boring bar blanks? I kinda thought you'd have to grind it out of a much larger blank taking forever and a day (and at least 2 full grinding wheels, hah)
Any tips/recommendations on bending it? What kinda radius bend could I put into a 1/2" square HSS bit before it starts cracking/snaping? does getting it to orange/yellow heat annel it? Or cause it to start burning like mild steel? (or do I just need to use less oxygen with my oxy/actylene torch?)

http://www.mini-lathe.org.uk/more_images/hss_lathe_tools.jpg something like the top right one pictured is what id love to be able to do.. Unless someone knows a place for blanks like that for cheap.

lazlo
01-16-2010, 01:05 PM
Did'nt think it would retain strength so hot.. I kinda allways thought when you started causing your HSS to change color (straw color, blue, etc) it was anneling the metal. (Sure I read that here somewhere.. that letting its color change was bad) And iv heard HSS is very hard to heat treat back to hardness so trying to heat treat again after grinding is out for HSM.

You're talking about the Red Hardness. Mild steel loses a lot of it's strength/hardness at 800° F. If you add cobalt to steel, it greatly increases the red hardness. HSS's typically have a red hardness in the range of 1100 - 1200° F. That's dull red. So keep the tip below dull red, and you're good to go.

Machinist-Guide
01-16-2010, 02:20 PM
And the following is taken from "Design and Use of Cutting Tools" by Leo St. Clair.
"One must grind tools in such a way as to produce as little heat as possible. The sudden overheating of the tool material while grinding causes a rapid expansion of the tool material surface that is next to the wheel. The tool material under the overheated surface is still cool and consequently not expanded.
The difference in expansion between the surface layer and the inner portion of the tool causes the tool material to check or crack. These grinding cracks weaken the edge area and cause it to break down rapidly through crumbling and chipping. Such cracks are often so fine that they cannot be seen by the naked eye."

Ed P

Thanks Ed this said it alot better then I could. I am a toolmaker not a writer
A lot of these guys think because HSS stays hard after it gets hot it's ok. But it's not. It will be hard but it will be full of microscopic cracks that lead to cutting edge break down.

lazlo
01-16-2010, 03:46 PM
From Moltrecht:

"If a coolant is not available on the grinder, the tool should be dipped in water, occasionally, to cool it."

CPM/Crucible Foundry also tells you to dip the toolbit while you're grinding it. I've posted it here before.

By the way Ed, are you Ed Huntress, the guy who started the famous "Don't Dip" thread on rec.crafts.metalworking?

small.planes
01-16-2010, 05:29 PM
Cant say Im a cool grinder. I tend to hold the bit in a pair of mole grips, and grind it fast.
Then I get on with cutting if Im roughing out, or I file it smooth with a diamond file if I need a sharp / fine finish.
I havent noticed any shortness in the life of my tools, and I dont fanny about taking little cuts (Industrial Size Lathes)
My HSS grinds last a similar amount of swarf to the indexable CNMG tips.
I do have a good stash of high quality HSS, Ultra Capital is one of the names marked down the side of some sticks.
I suspect some of the import 'HSS' is one step up from Plasticine...
Ive certainly had some HSS hacksaw blades that were as much use a a cheese string.

Dave

gwilson
01-16-2010, 05:36 PM
First of all,I wish all the experts knew the difference between a belt sander and a BELT GRINDER. The latter is what you have been talking about.

And yes,there will be a little round over at the top of the tool,I don't care how tight you get the belt,or how flat it is against the platen,it always bulges.

I haven't waded through all 5 pages of this,but no one has thought that the platen might be a little worn hollow. That can cause the bulge,too.

I make my platens out of fully hardened A2 steel,and screw them over the original cast iron platen after it has gotten worn. I flip over the A2 platen after it wears,and make a new one when it finally gets a dollop ground in it that is too deep.

No matter where I grind,though,on my new platen,I still see a very fine bit of roundness. It just can be worse with a worn platen,and they don't take long to wear.

I cannot agree that a "sander" will heat up an edge faster than a wheel grinder. That is just not true.

About getting red hot: HSS is TEMPERED at about 1000 degrees F,which IS red hot.

About BENDING it,if you get HSS TOO HOT,like yellow,it may fall apart. I had a hack blacksmith let that happen when I had to go to his shop before I had a forge. I was making some boring bars out of annealed,new HSS. I sort of had to let him heat up the metal because of his big ego. I kept telling him "Don't let it get too hot!" The end fell off the bar when he took it out of the fire. I took the rest of the damned expensive bar away and made the tools elsewhere.

You can bend it if you buy new,UNHARDENED HSS material,and have the means to harden it properly. I think that many of the old,shop made boring bars were really not hardened properly,but still worked quite well,by just forging them and heating to red hot,then letting them cool. I have done that myself,and made some VERY hard,and VERY tough boring bars.,though they are supposed to be hardened at MUCH higher temps.,and tempered at about 1000 degrees.

As for quenching HSS,there is an argument that quenching can cause micro cracks in it. I DO quench,but I never let the HSS get very hot at all. Usually I grind just a few seconds between quenches. What I do,is grind with the quench water still on the bit. As soon as it starts to sizzle,it is instantly quenched again.

Boucher
01-16-2010, 06:55 PM
I started the thread and it looks like I used the wrong term in the second sentence. For clarification this is what I was talking about using:
http://i109.photobucket.com/albums/n50/boucherbyron/IMG_0065.jpg
That is my coolant bucket there on the floor. The Baldor grinder is on the left. I was in the process of changing the grinding wheel when I came to the house for supper.

These threads often go in completely different directions than the Question ask. gwilson said:"And yes,there will be a little round over at the top of the tool,I don't care how tight you get the belt,or how flat it is against the platen,it always bulges."

Thank you for answering the original Question.

Even though they go in unforseen directions the discussions add to out knowledge base.

vpt
01-16-2010, 07:03 PM
Yes it is all good information! At least it was all relevant.

One forum I frequent (local friends) never stays on topic. Normally within 3 posts it will be so far off topic its funny. OT will be brakes on a car, by the 4th post or so they will be talking about pizza or how cold it is outside. :D

clutch
01-16-2010, 07:36 PM
By the way Ed, are you Ed Huntress, the guy who started the famous "Don't Dip" thread on rec.crafts.metalworking?

I've corresponded enough with Ed that I can vouch that he isn't Ed Huntress. Different writing style.

Clutch

John Stevenson
01-16-2010, 07:51 PM
I made some slotting tools for keyways, I needed 8 mm and 10mm so bought a couple of lengths of 8 x 10 HSS and cut some slots into a 1" square steel bar and brazed them in, that got them red hot for a start.

Then found out that the 8 x 10 was nominal and a bit under size which was no good. No point reordering as every piece of stock HSS was also nominally under size and I had made the tools and rough ground to shape.

Sooo, reheated the end the cherry red and whacked it with a BFH to mushroom the end over size, allow to cool then grind to size.

So far the 8mm one has cut about 300 blind keyways in winch handles and has been reground about 3 times, the 10mm one is still unused as yet.

.

vpt
01-16-2010, 08:13 PM
I wounder if these conflicting stories have something to do with what companies the HSS came from? Maybe some HSS is better than others?

John Stevenson
01-16-2010, 08:18 PM
I wounder if these conflicting stories have something to do with what companies the HSS came from? Maybe some HSS is better than others?

Well the 8 x 10 I bought was from China, most other HSS I have could have come from anywhere as it's all old stock,

gwilson
01-16-2010, 09:34 PM
There are MANY types of HSS. You need to research it.

Boucher,glad to have answered your question. Most certainly your little belt grinder will have limited belt tension to stop the belt from bagging. I use a Wilton Square Wheel grinder. Rather ugly,but maybe the most versatile and easily re- configured grinder out there. Still not the fastest,or most aggressive type,though. Those tilted horizontal types have very high belt speeds,and can grind a 45 degree angle on the square end of 2" angle iron in just a few seconds. They throw huge rooster tails of sparks,though,and at least I can vacuum mine while being made,to keep the shop clean of nasty dust. I have a dedicated Delta hooked up to it.

gwilson
01-16-2010, 10:11 PM
I haven't tried to hammer red hot HARDENED HSS,but made some very hard and tough steel die sinker's chisels from M33 annealed stock. I hammered them down from 3/8" square to 1/8" square at their tips while heating only to dark red. My intention was to crush the carbides into a tiny matrix at that low heat. This is how Wootz,or what we incorrectly call Damascus steel was made. Damascus was the name given to "watered" patterned steel that Europeans made trying to duplicate the Wootz. Bear in mind that no one knew anything about the chemistry of what they were doing ,Wootz or otherwise,at that time.

I let them air cool afterwards. At the Williamsburg gunsmith's shop,one of the guys cut up the shank of a Nicholson file until he got to the hardened area. I told him to keep going,and it cut about 1/4" into the hardened part of the file before the tip broke off.

Wootz steel was very high carbon steel made in a crucible and sold in the shape of a hockey puck. The Eastern smiths forged it into sword blades at a low red heat. Both the Wootz,and my HSS were about as hard to hammer as COLD mild steel. However,they crushed up the carbides very small,leaving them in a matrix of softer steel. This made their blades take an extremely sharp edge,and yet be tough. Somehow they fell into this process without realizing what they were doing to the steel. It could have been that they thought that the more work they put into the steel,the more work it would give,or some such philosophy,but it worked!

I can't recall my reasoning at the time I did this,but some years later some scientists figured out how to do it the same way as I had! They rolled red hot high carbon steel through a powerful rolling mill and accomplished it.

Since steel is more easily forged at much higher temperatures,European smiths forged steel much hotter. That melted the carbides,however,and they cooled into bigger structures when quenched,making brittle,hard steel,that had to be drawn softer to add toughness.

I still use those chisels,and still have some bar stock left. Got it from Latrobe.

oldtiffie
01-16-2010, 10:33 PM
I made some slotting tools for keyways, I needed 8 mm and 10mm so bought a couple of lengths of 8 x 10 HSS and cut some slots into a 1" square steel bar and brazed them in, that got them red hot for a start.

Then found out that the 8 x 10 was nominal and a bit under size which was no good. No point reordering as every piece of stock HSS was also nominally under size and I had made the tools and rough ground to shape.

Sooo, reheated the end the cherry red and whacked it with a BFH to mushroom the end over size, allow to cool then grind to size.

So far the 8mm one has cut about 300 blind keyways in winch handles and has been reground about 3 times, the 10mm one is still unused as yet.

.

Thanks John.

I've been waiting for something like that.

I just heat and forge ("adjust") HSS tool-bits if and as required. I freely use and admit to silver-soldering them to boring bars or anything else. Until I got my MIG welder I used the "chokey" "stick" welder to do the job on occasion. I use the MIG and oxy-acet now.

All of 'em work to my satisfaction. My shop is just a small occasional-use hobby shop and while the HSS bits may (or may not) be too much less than new they do the job - if I let 'em.

If I want a HSS boring bar or an off-set tool, the oxy-acet and the anvil and BFH do the job in fine style. It sure beats the tripe out of beating the tripe out of the grinders.

I buy very good OZ-made HSS tool bits as I take no chances on them. I have used some imported HSS tools (not all from Asia) and they do pretty well for the cost.

Wot werkz wurkz.

Ian B
01-17-2010, 04:15 AM
Black Moons,

Yes, I was trying to make a small boring tool, by bending the end of the 5mm rod, ready to be ground. Maybe I should just have applied more force, but reading that hot HSS is as hard to form as cold mild steel makes sense - it just didn't want to bend.

BFH time...

Ian

Oh, on the quality of the HSS I was using; it was Chinese, bought in Cairo. No dodgy-quality stuff in my home shop!

oldtiffie
01-17-2010, 04:32 AM
Ian.

I presume you have a tool/adaptor for the shank of the 5mm HSS boring bar - so I will leave that alone.

Instead of "forging" the end around (use "barely red" colour if you need to forge it - its tough and the BFH will get a work-out) - why not just use a 1mm (~0.040") or 1.5mm (~0.060") cut-off wheel in your angle-grinder and cut say 1/2" (or to suit) off the end and put/grind a "flat" (for welding) and silver solder/braze the two bits together.

Its a lot easier and won't over-heat the HSS.

Then grind to suit.

I rough grind mine with an angle-grinder with the tool in a vise (use a bucket of water for cooling). Then I finish off on the front of my pedestal grinder or belt sander front roller (for a hollow-ground finish) and then finish off with diamond hand hones (use water).

Black_Moons
01-17-2010, 04:37 AM
Yea I guess silver soldering it is likey a better idea... What should I look for in a silver solder for applications like this? Just generic lead-free silver plumbers solder or what?

Bending the HSS just seems cooler :P I wonder if anyone sells those offset blanks cheaply enough..