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parrisw
02-06-2010, 07:55 PM
Ok, I set up my grinder yesterday with a white alu oxide wheel, though the only grit I could get locally was 60, is that going to be too rough? What should I do after? I've heard of lapping them in? With what kind of stone?

Fasttrack
02-06-2010, 08:37 PM
Not "lapping" but "honing".

To get a really keen edge, you can touch the bits up with an oil stone. I normally don't bother. I rough in the bit with a 60 grit aluminum oxide wheel and touch it up on an 80 grit silicon carbide wheel because those are what I have on my grinder ;)

It's not rocket science. The geometry is the most important part - if you can get that down, then you can worry about getting a really good cutting edge with different wheels, etc.


The stone you use for honing can be bought from various places as a sharpening stone, or you can use a piece of a grinding wheel (a fine wheel). I had a 120 grit? (iirc) wheel that was too small to use as a grinding wheel anymore so I broke it into pieces.

parrisw
02-06-2010, 08:44 PM
Thanks!! I'll hopefully give it a shot this weekend.

Oh, are there any certain angles to go by for a right hand and left hand bit? I know the 10° on the front, but what about the shape of the cutter? If your looking from the top, I know the approximate shape, but does it have to be exact?

Dr Stan
02-06-2010, 09:22 PM
Thanks!! I'll hopefully give it a shot this weekend.

Oh, are there any certain angles to go by for a right hand and left hand bit? I know the 10° on the front, but what about the shape of the cutter? If your looking from the top, I know the approximate shape, but does it have to be exact?

Pick up a copy of "How to Run a Lathe" by South Bend Lathes. It has excellent drawings for many lathe tools. Just keep in mind these were designed for use in a rocker type tool post and you will need to modify the front angle if you are using a drop in (Alloris type) tool post.

Black_Moons
02-06-2010, 10:35 PM
the angles are a function of many things.. realise you'll likey want bits with all kinds of front/side angles and nose radiuses so just give it a shot and see how it works, if it sucks you can just adjust the grind.

Lots of people here use hand diamond coated laps of verious grits (150~600) to put the final hone and fine tuning of angles on HSS bits
Also, dremels (mainly the cutoff wheels) can be used for things like roughing in notchs for chipbrakers etc, and diamond coated files can be used to smooth them out and get them to the desired size.

smiller6912
02-06-2010, 10:40 PM
I think that this is a good place to start learning about grining a tool.....
http://www.sherline.com/grinding.htm

And, if you scroll down to "TOOLS AND EQUIPMENT
GENERAL PURPOSE CUTTING TOOLS ", there is a good description of tool shapes (geometry) here..........
http://www.americanmachinetools.com/how_to_use_a_lathe.htm

parrisw
02-06-2010, 10:42 PM
Ok, just went and made a left hand cutter, angles to 10°, and a top plate relief of 10° as well, I think I need that with the QCTP(aloris style). Tried it right off the grinder on some mystery steel, and seemed to pull a good chip. I'll keep playing.

MotorradMike
02-06-2010, 10:45 PM
This guy (http://www.youtube.com/watch?v=hrDr4rYLiAk) is worth watching.


Mike

parrisw
02-06-2010, 10:50 PM
This guy (http://www.youtube.com/watch?v=hrDr4rYLiAk) is worth watching.


Mike

Yes, thanks. I've watched all his vids many times!!

Black_Moons
02-06-2010, 11:02 PM
parrisw: Congrats! success.
I mean, if it seems to cut, then it works and its a success. Next see how good a finish you can get on verious materials (realise mild steel almost allways results in a poor finish, aluminum alloys are much easyer most of the time)
Finish is mainly a factor of the nose radius, and how smooth its cutting edge is (as in, no tiny chips from a rough sanding process) (I make small radiuses JUST with the diamond file, no need for the grinder, larger radiuses might be roughed in ever so carefuly on a grinding/sanding tool, a tiny point of contact = large amount of metal removed easily)

Or if you can get your bit to produce short chips insted of long stringy ones.

parrisw
02-06-2010, 11:07 PM
parrisw: Congrats! success.
I mean, if it seems to cut, then it works and its a success. Next see how good a finish you can get on verious materials (realise mild steel almost allways results in a poor finish, aluminum alloys are much easyer most of the time)
Finish is mainly a factor of the nose radius, and how smooth its cutting edge is (as in, no tiny chips from a rough sanding process) (I make small radiuses JUST with the diamond file, no need for the grinder, larger radiuses might be roughed in ever so carefuly on a grinding/sanding tool, a tiny point of contact = large amount of metal removed easily)

Or if you can get your bit to produce short chips insted of long stringy ones.

Thanks!! I'll go take a pic of what I did, then you guys can see if I did any good!

parrisw
02-06-2010, 11:16 PM
Ok here is a few pics. Criticize me please!!

http://i278.photobucket.com/albums/kk107/parrisw/IMG_0854.jpg

http://i278.photobucket.com/albums/kk107/parrisw/IMG_0853.jpg

http://i278.photobucket.com/albums/kk107/parrisw/IMG_0852.jpg

I think the finish actually came out better then the carbide I was using.

lakeside53
02-06-2010, 11:37 PM
Sure it did.. your lathe can't really spin up or take the load carbide needs... You'll be much happier with HSS for much of what you'll do.

parrisw
02-06-2010, 11:46 PM
Sure it did.. your lathe can't really spin up or take the load carbide needs... You'll be much happier with HSS for much of what you'll do.

Thanks!! Ya, I should of done it sooner, rookie I guess, LOL. Now just need to make ummm at least another half dozen bits, and more.

mf205i
02-07-2010, 05:11 AM
Your bit looks nice but it appears to slope down with negative back rake. It needs to slope upward, positive rake, as it is presented to the work, a hook. Try about 16 degrees for finish on mild steel with a rounded tip or a VERY SMALL flat on the point. Honing your finish bits seems to help control built up edge and improves finish but does little on a rougher. Increase speed for the last light finish pass and use a sulferised cutting oil.
Check out these.
http://www.archive.org/details/textbookofadvanc00smituoft
http://www.youtube.com/user/mrpete222#p/u/72/mArZFFCQDek GREAT VIDIOS
http://www.bbssystem.com/manuals/Lathe-Tutorial.pdf
http://metalwebnews.com/machine-tools/fmt.html
See HTRAL at http://www.wswells.com/index.html
http://www.jjjtrain.com/vms/library.html
https://atiam.train.army.mil/soldierPortal/appmanager/soldier/start?_nfpb=true&_pageLabel=rdlservicespage
http://opensourcemachine.org/node/10
http://www.metalwebnews.org/ftp/machinery-repairman.pdf
http://www.americanmachinetools.com/how_to_use_a_lathe.htm
http://www.sherline.com/grinding.htm
http://www.machinist-guide.com/lathe-threading.html
And don’t forget to download your FREE copy of Machinery’s handbook, Edition 5, at Google books.
http://books.google.com/books?id=VkEYAAAAYAAJ
And if you have an Atlas or Craftsman product, http://www.roseantiquetools.com/id116.html
Have fun, Mike

Black_Moons
02-07-2010, 06:37 AM
those chips look pertty...black, generaly with HSS VS mild steel you want to stay at 100SFM and at worst, have chips that are 'golden'/straw colored.

looks like an OK finish for mild steel. bit looks fine except for the mentioned negative rake, usally you want the top flat or pointed upwards as noted (Yes this means there must be a 'groove' on the top of the bit to make the top point upwards)

Good job.

ps: you don't need to grind the 'leading' side down so much, infact you can pertty much leave it at 90 degrees if you really want for turning to a shoulder without turning your toolpost around.

the important part is to grind a relief.. it also looks like your tool might have very little to no relief. Feeding fast with no relief results in the work rubbing on the lack of relief.

Your Old Dog
02-07-2010, 06:51 AM
................
looks like an OK finish for mild steel. bit looks fine except for the mentioned negative rake, usally you want the top flat or pointed upwards as noted (Yes this means there must be a 'groove' on the top of the bit to make the top point upwards)....................

It looks to me from the photo that the actual tip of the cutter takes a slight nose dive? If so, that will cause it to rub more then cut and that will make for an ugly finish. I do best when the absolute tip of the bit points up by 2-4 degrees. I do that by doing the Dremel cutoff wheel to make a chip breaker.

I occasionally leave the top of a cutter flat but use it dead on center with the work. It works but I seem to do best with the chip breaker that helps create the top rake.

Here's a borrowed pic of what my bits look like.

http://www.penturners.org/olduploads/skiprat/2008321155945_grinderjig7.jpg

small.planes
02-07-2010, 06:51 AM
Your grinding looks fine, but why have you removed so much from the sides?
It takes longer to grind, and as long as the *included* angle is less than 90 degrees it'll still turn up to a square shoulder, you just have to present it to the work at a slight angle. (rotate toolpost or topslide).

This is an equivalent tool from my unimat. It has a dead sharp point (although I notice in the photos it needs touching up) as I used it on tiny parts which needed a sharp inside corner. You can shave a tiny sliver off with it. The side clearance was just put on by touching the side to the grinder square, but rotated about 10 degrees around its long axis if you see what I mean.

Top:

http://i306.photobucket.com/albums/nn274/small_planes/07022010102.jpg

Side:

http://i306.photobucket.com/albums/nn274/small_planes/07022010103.jpg

End:

http://i306.photobucket.com/albums/nn274/small_planes/07022010104.jpg


Other handed Round nosed tool, again with minimal grinding to get the required shape:
http://i306.photobucket.com/albums/nn274/small_planes/07022010105.jpg

hth

Dave

John Stevenson
02-07-2010, 07:03 AM
OK, I'm going to stick my neck out on the line.

Incommmmming..........

I use a small grinder which is no more than a 3000 rev motor with a couple of small 4" diamond wheels on it and use this for fine grinding of HSS and carbide.

Now the purists will say don't grind HSS with diamond as the carbon from the steel will degrade the diamond and black holes and dwarfs appear.

This may be true but with wheels at less than £10 a pop now, sod it I couldn't care, having said that I'm still on the same wheels I bought 5 years ago.

Anyway if the carbon goes from the HSS to the diamond then do I get carbon credits ?

Seriously I find it works with no problems, I don't have any tool rests just present the work to the wheel freehand, tool rests get in the way and we are not taking about ripping off 1/4" at a time, just taking a lick.

.

Black_Moons
02-07-2010, 07:22 AM
John: are you using those masonary wheels with the like, 9 diamonds scattered across the entire wheel?

Considered trying to use the face of a standard grinding disk in your angle grinder? Or the tip for some really nasty gouge roughing..
or a sanding disk? (recommend 46/60 grit zerconia for roughing)
Flap disks work too but they seem to dull out quickly.. and if you get the conical ones its hard to judge the angle your holding the bit.

Belt sander with zirconia paper works too.

Id be intrested in hearing how your diamond wheel removal rates hold up to these methods. for one I know sanding gets kinda slow once you have a large face to grind (like the larger face of an offset threading bit outta 3/8" or thicker HSS, starts taking forever to grind)

John Stevenson
02-07-2010, 07:47 AM
BM,
No using these type of wheel, the bottom of the page types as opposed to flat wheels.

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

I have used one of the angle grinder diamond wheels for roughing on carbide and they do remove stock very well but you can't get a good edge, it very friable when looked at under a glass.
However, and this is carbide if you grind with a angle grinder then 'hone' on one of these wheels you get a good finish and edge.

Same for HSS just rough out on a normal grinding wheel, then hone.

Metal removal rates are very slow with these wheels, they are only for getting a finished edge.

I'll get some pics later when i go in the shop.

Black_Moons
02-07-2010, 08:19 AM
Intresting wheels. Nice price too
odd that they don't list any grits however.

John Stevenson
02-07-2010, 08:26 AM
That was my take on this, years ago when a diamond wheel was about £100 the stories of them being ruined was enough to put anyone off but nowadays they are throw aways, although I haven't thrown any yet :D which rather proves my point.

Grit size from rubbing a finger over is probably the same as 800 to 1200 wet and dry.

Peter.
02-07-2010, 09:26 AM
Looks to me that those 'resin bonded diamond' wheels are the type which keep themselves sharp by erosion. New diamond is exposed to the tool being ground. One which I bought last year has a single coating of diamond electroplated on a steel disc. I think these are the sort that would be ruined by grinding HSS if any.

Diamonds do cut HSS or mild steel so long as they are kept cool. I've been doing it for many years cutting concrete with steel reinforcement.

kjbllc
02-07-2010, 10:43 AM
i did a quick search on google about those wheels and don't seem to come up with much, at that price, I guess you are closer to india suppliers.

parrisw
02-07-2010, 12:13 PM
Your bit looks nice but it appears to slope down with negative back rake. It needs to slope upward, positive rake, as it is presented to the work, a hook. Try about 16 degrees for finish on mild steel with a rounded tip or a VERY SMALL flat on the point. Honing your finish bits seems to help control built up edge and improves finish but does little on a rougher. Increase speed for the last light finish pass and use a sulferised cutting oil.
Check out these.
http://www.archive.org/details/textbookofadvanc00smituoft
http://www.youtube.com/user/mrpete222#p/u/72/mArZFFCQDek GREAT VIDIOS
http://www.bbssystem.com/manuals/Lathe-Tutorial.pdf
http://metalwebnews.com/machine-tools/fmt.html
See HTRAL at http://www.wswells.com/index.html
http://www.jjjtrain.com/vms/library.html
https://atiam.train.army.mil/soldierPortal/appmanager/soldier/start?_nfpb=true&_pageLabel=rdlservicespage
http://opensourcemachine.org/node/10
http://www.metalwebnews.org/ftp/machinery-repairman.pdf
http://www.americanmachinetools.com/how_to_use_a_lathe.htm
http://www.sherline.com/grinding.htm
http://www.machinist-guide.com/lathe-threading.html
And don’t forget to download your FREE copy of Machinery’s handbook, Edition 5, at Google books.
http://books.google.com/books?id=VkEYAAAAYAAJ
And if you have an Atlas or Craftsman product, http://www.roseantiquetools.com/id116.html
Have fun, Mike


Ok now I'm a little confused. What do you mean by slope down? Are you talking the top of the bit? I thought the top plate must slope back and down a bit?

parrisw
02-07-2010, 12:15 PM
those chips look pertty...black, generaly with HSS VS mild steel you want to stay at 100SFM and at worst, have chips that are 'golden'/straw colored.

looks like an OK finish for mild steel. bit looks fine except for the mentioned negative rake, usally you want the top flat or pointed upwards as noted (Yes this means there must be a 'groove' on the top of the bit to make the top point upwards)

Good job.

ps: you don't need to grind the 'leading' side down so much, infact you can pertty much leave it at 90 degrees if you really want for turning to a shoulder without turning your toolpost around.

the important part is to grind a relief.. it also looks like your tool might have very little to no relief. Feeding fast with no relief results in the work rubbing on the lack of relief.

Ok, I think I know what you mean now. The top of the bit the leading edge does point up not down, maybe its just not enough. What kind of angle should I normally use? I set it to 10°, and where is the relief you mean? If I'm thinking right, the blank came with a front relief ground in already, so that's the angle I used to grind the rest. What kind of relief angle should I use? I think its more then 10°. I need to get an angle finder or something.

parrisw
02-07-2010, 12:23 PM
Ok, I looked at the pics posted, should of done that before my last replies, I see what you guys mean now. A pic is worth a thousand words!! I see what I need to do now.

I don't know why I ground so much off the edges, I guess I just thought that's what its supposed to look like. Oh well, next time I'll do less. Thanks everyone, and to the ones that posted pics.

Black_Moons
02-07-2010, 12:32 PM
parrisw: Don't worry, its still a wonderful bit. good for puting a large 45degreeish chamfer on soft materials :) (And a smaller chamfer on hard materials) without using the compound.

parrisw
02-07-2010, 12:46 PM
parrisw: Don't worry, its still a wonderful bit. good for puting a large 45degreeish chamfer on soft materials :) (And a smaller chamfer on hard materials) without using the compound.

Thanks, I'm not too worried about it. Not the first thing I've messed up. LOL. I'll play with this bit some more. I'm going to give the top some more relief and try cutting again. Its ok for my first go at it.

Hey, where in BC are you? I'm in Victoria.

parrisw
02-07-2010, 04:10 PM
Ok, went out and ground the top plate with some relief, just did it by eye, and man what a difference!!! Never in a million years I thought I would get that good a finish on Steel, I'll take a pic in a bit. The only thing is, it creates a very long chip? How do I get rid of that? Or does it matter?

Toolguy
02-07-2010, 04:17 PM
Make the same top relief short - maybe .100 or so back from the point. Then the chips will curl up and be small. They will run into the vertical part of the top relief and be redirected.

small.planes
02-07-2010, 04:21 PM
Either grind a chipbreaker in, or stop start the feed, which will stop the cut, and end the chip.
Chipbreakers are a bit of an artform IME.
If I have to grind one then I usually use a cuting wheel in a dremmel and use it to put a 'gash' at roughly parrallel to the front face of the tool. The idea is to interrupt the flow of the chip so that it breaks up into smaller pieces.
With carbide inserts chip breakers are usually moulded into the inserts, take a look at a catalogue of inserts to get an idea of what to grind in.
The round nosed tool I posted earlier makes really tight curly swarf, you can see the channel that creates it in the photo.

You can sometimes get the same effect by playing with speeds and feeds, usually going fast in sfm will break the chip up, but watch you dont end up just burning away your tool.

Dave

Toolguy
02-07-2010, 04:25 PM
It's not practical to start and stop the carriage when cutting a thread. Some other method of breaking the chip is needed.

small.planes
02-07-2010, 04:30 PM
You are correct, but when 'just turning' (as the tool ground is a turning tool) and especially when roughing out it is a simple, guaranteed way to break the chip.

Dave

John Stevenson
02-07-2010, 05:11 PM
First the simple grinder.

http://www.stevenson-engineers.co.uk/files/T&Cgrinder1.jpg

No apologies for the crap picture as it doesn't get much use now I have the MKII, there is another one under that pile of crap somewhere with two diamond wheels, one either end. This one only has one diamond wheel and two white oxide wheels for odd freehand grinding.

http://www.stevenson-engineers.co.uk/files/T&Cgrinder2.jpg

This is the MKII, it's one of the Chinese copies of the Deckel.
These are advertised as Tool and Cutter grinders but in fact they are SINGLE LIP tool grinders, a big difference but I don't want to get into this here.
Scattered about are some of the different wheels for it, some pre mounted on arbors and a couple of new ones on top.

Because this is handier to use it's taken over from the MKI but even though i have all the attachments, including a lathe tool holder i still use it freehand.

http://www.stevenson-engineers.co.uk/files/tool1.jpg

This is a shot of the tool after it's been on the diamond wheel, it's hard to get a clear picture because of the reflections but it's a very polished finish and really sharp.

http://www.stevenson-engineers.co.uk/files/tool2.jpg


.

parrisw
02-07-2010, 06:06 PM
Thanks again for all the tips, I really appreciate it. I'm pretty happy with how its going. For my first bit, its working really well.

Black_Moons
02-07-2010, 06:48 PM
Your tip still looks like its pointing down not up.
http://upload.wikimedia.org/wikipedia/commons/0/0e/Tool_Bit_Geometry.JPG Note the 'back rake' angle. That is very important to be pointed back as shown (for a typical HSS tool)
Don't worry about 'side rake' it isnt quite as important

parrisw
02-07-2010, 07:03 PM
Your tip still looks like its pointing down not up.
http://upload.wikimedia.org/wikipedia/commons/0/0e/Tool_Bit_Geometry.JPG Note the 'back rake' angle. That is very important to be pointed back as shown (for a typical HSS tool)
Don't worry about 'side rake' it isnt quite as important

Thanks, that's a good drawing. I haven't showed a pic yet of how it is now. I'll go take a pic.

parrisw
02-07-2010, 07:14 PM
http://i278.photobucket.com/albums/kk107/parrisw/IMG_0855.jpg

http://i278.photobucket.com/albums/kk107/parrisw/IMG_0856.jpg

http://i278.photobucket.com/albums/kk107/parrisw/IMG_0858.jpg

Peter.
02-07-2010, 07:21 PM
Your end cutting edge has a shallow curve in it, try to grind it straight or you won't be cutting on the radius part of the tip.

Black_Moons
02-07-2010, 07:22 PM
Oh that was johns bit, haha. Looks good, you'll likey notice with a chipbraker like that ( a big one) that heavy feeds produce nice crumpled chips while lighter feeds make long stringy/curly chips (Curly are much safer then straight/stringy! Straight/stringy chips are like strong razor blades and could pull you in if they wrap around the chuck and you, or slice you up, curly ones usally snap if you pull on em)

the sorta threaded look thats left is likey due to an imperfection on the nose of your toolbit (Use a hand hone (stone or diamond) to fix) or too high a feed rate or cut of depth (take another pass at say 0.002 mils deeper and slowest feed you have)

The fact you can still see lines clearly on the bit indicates its not honed very well
a well honed bit, starts looking mirror shiny with just micro streaks.

Honing the top can help improve chip flow and reduce material buildup on the tip.

parrisw
02-07-2010, 07:57 PM
Oh that was johns bit, haha. Looks good, you'll likey notice with a chipbraker like that ( a big one) that heavy feeds produce nice crumpled chips while lighter feeds make long stringy/curly chips (Curly are much safer then straight/stringy! Straight/stringy chips are like strong razor blades and could pull you in if they wrap around the chuck and you, or slice you up, curly ones usally snap if you pull on em)

the sorta threaded look thats left is likey due to an imperfection on the nose of your toolbit (Use a hand hone (stone or diamond) to fix) or too high a feed rate or cut of depth (take another pass at say 0.002 mils deeper and slowest feed you have)

The fact you can still see lines clearly on the bit indicates its not honed very well
a well honed bit, starts looking mirror shiny with just micro streaks.

Honing the top can help improve chip flow and reduce material buildup on the tip.


Thanks. Ya, I don't have anything to hone the bit with. That's just off the grinder 60grit alu oxide wheel. The chips were long, but really tight curl.

kjbllc
02-07-2010, 08:03 PM
This is probably a dumb question, but is it a bad idea to use a belt sander, bench model for the tool bits? Or is it better to use the grinder wheel for the hollow grind and the belts are not that good for HHS. thanks. kevin

Black_Moons
02-07-2010, 08:53 PM
Belts are fine, I perfer the flat grind myself, but many perfer hollow (less surface to hone afterwards)
I recommend zerconia belts, like a 46 and a 60 for roughing, Aluminum oxide belts seem to dull rather fast on HSS.. or rather, at least all the highly agressive grains get broken quick and your left with a much tamer belt quickly (But then it wears rather slowly)

Some say the belt causes a slight rounded over lip, just hone a little more if your worryed, and idealy grind with the cutting edge tailing in the direction of the grind, especialy as its easy for a belt sander to 'grab' a bit and it suddenly will walk a few degrees up in your hand, rounding it over.. rounded bottom = no problem, rounded cutting edge = fail.

kjbllc
02-08-2010, 08:47 AM
thanks I have both, grinder and belts, but at this point in time the guide/table on the belt is better, I need to make a table for the grinder, since I do have good wheels on them, I use them for wood turning tools. thanks. kevin

Black_Moons
02-08-2010, 09:15 AM
Most people grind HSS freehand, give it a try, its not hard once you get used to placing the steel back on the wheel, the bit basicly guides itself back to the right angle, so you try and just land on the bottom edge and let it roll back to the correct angle.. adjustment in pressure can vary the angle your grinding without that annoying multi facet effect.

Boucher
02-08-2010, 10:16 AM
This is probably a dumb question, but is it a bad idea to use a belt sander, bench model for the tool bits? Or is it better to use the grinder wheel for the hollow grind and the belts are not that good for HHS. thanks. kevin
It is not a dumb question. I have asked the same question several times. There are some that say the belt rounds the top edge. I am still evaluating that. One thing is sure. The belt sander is much faster and cooler grinding than the wheel grinders. That makes it a better choice for roughing. The best quality wheels and belts are far superior to the others. It is worth the time and cost to get it right. I had what I thought was good grinding wheels. I recently bought the correct Norton and it is amazingly better than the old ones.

There are some facts that are technically correct but practically not significant. The use of the diamond wheels to dress HSS is in that category.

One thing that is certain is that HSS is the better tool of choice for many home shop applications. The knowhow to produce these tools is important. I got a box of old tools from a shop closing. There are many very interesting shapes in that box. There were two oldtimers who were working there when the owner decided to close the shop. I really wish they were still avaliable to pick their brains.

Black_Moons
02-08-2010, 10:38 AM
Oh, one thing that will DEFINATELY cause problems if you try and grind the HSS bit on a belt sander with the 'cutting' edge leading insted of tailing, is the join on the belt, thats basicly a lump and will likey round the leading edge of whatever your grinding slightly. (of course, agressive honeing will fix that, its just a pain)

But again, just flip the bit around and no problem.

Boucher
02-08-2010, 12:02 PM
When grinding lathe tools on the belt sander one should tilt the table to the 7° relief angle. That prevents simply turning the tool upside down. With the tool flat on the table it is easy to free hand the other angle. It is also easy to make a simple guide and make it really look good. I will post some photos later. I think the concept of the belt pulling slack above the tool and rounding the top cutting edge is absolute BS. There may be differences in belt sanders that account for this, but I am not seeing it with mine. (and yes I am calling it a belt sander even though it may be more correctly a belt grinder) It is very easy to change belts and use finer grits to produce a smoother surface. The reality is that the finish underneath the cutting edge is not significant. It does however please me as I have been accused of being a compulsive perfectionist. If the table on the tool grinder is set the same as the belt sander table then a short brush to the wheel will recondition the entire surface. I was initially taught to completely freehand grind tools. This was on large Baldor pedestal grinders which were very nice to use. I am not ready to take off the traning wheels so to speak and throw away my grinding jigs. The tools that I free handed didn't look as good but they cut just as good. Adequate relief is necessary but most of the rest of the angles are not critical. Good chipbreakers are the hardest to establish.

kjbllc
02-08-2010, 05:08 PM
thanks again for all the help, I will make some notes on this for reference.

parrisw
02-26-2010, 10:58 PM
another question. I did some cutting on a aluminum piston out of a chainsaw, and the finish didn't turn out too great? Should I be sharpening it different for alu?

kjbllc
02-27-2010, 09:03 AM
boucher, I was wondering if you got around to the pics? thanks.

Your Old Dog
02-27-2010, 10:15 AM
Thanks. Ya, I don't have anything to hone the bit with. That's just off the grinder 60grit alu oxide wheel. The chips were long, but really tight curl.

I use a Hard Arkansas stone and it works fine. You won't think you are doing anything as the stone is like ceramic but you are. You only have to hone the anbsolute cutting edge and not the entire bit. Therefore, holding the bit in one hand and the stone in another you can put tremendous pounds per square inche force on it. When you are done, you will notice the absolute cutting edge looks polished and it is. That is "the" finish that you will impart to the work. When engravers want a bright or polished looking cut they hone the edge on either a Hard Arkansas stone or drag it backwards on a piece of 4/0 jewelers paper resting on a piece leather.

Even though you won't feel like you are doing much, the Hard Arkansas stone will work fine. You can get them at sporting good stores. Mine is .5x.5 x3" long. To use it you try to square the tip area flat on the stone and drag it backwards about 3 times per each of top, l side an r side of tip.

I would not use a sanding belt, sidewalk or side of a brick building to sharpen your bits unless there is absolutly nothing else available and Sears is closed so you can't buy a $20 grinder :D Look for an industrial supply house in your phone book and go buy yourself a 60 grit white or pink stone. They cut fast and cool compared to other stones. You can take the bit off that stone and use it but it works better if it is taken to a green carbide cutting type of stone and then honed as described above.

BTW, I find when shaping the back angle on a new piece of bit that I do it as the first step in making a chisel. This is a very slight angle in my case and easy to overdue if I've already done the two sides as it won't have as much support.