Sharpening Lathe Tools

[David Osborne 1Participant @davidosborne1]

Hi

 

I have recently purchased an old Delta Tool Co Carbide Tool Grinder. It is a well engineered machine with a double ended spindle, one end having a Silicon Carbide Wheel and the other end a Diamond Lap. There is a double angled tool rest at each end and the motor is reversible.

 

My question is:- Is it ok to sharpen and hone HSS lathe tools on this machine, or will it damage the two wheels, or significantly reduce their life.

 

Dave O

[David Osborne 1Participant @davidosborne1]

[KWILParticipant @kwil]

You will need a white wheel for the HSS, the diamond lap will be OK for the final edge

[Paul NarramoreParticipant @paulnarramore61033]

Would you please elaborate? I'm new to lathe work and will need to sharpen HSS lathe tools. What exact wheel would I need, thanks? Presumably one which attach to a bench grinder?

[Neil WyattModerator @neilwyatt]

I'll second what KWIL says.

Some will tell you that HSS will spoil a diamond wheel (because hot iron atoms pull the carbon out of diamonds). In practice I've been using a diamond wheel on HSS for years and it works really well, but 0.001" is a heavy cut…

HSS will sharpen on a green grit wheel but it WILL disappear rapidly. It will ahve a soft compound as it is for grinding hard carbide (yes I know, go figure it out).

Better to get standard grey or ideally white aluminium oxide wheels for HSS.

Paul, a standard double ended bench grinder is a good start for lathe tools and will probably come with suitable fine and medium (or slightly less ideal medium and coarse) wheels. They do need to be properly supported with minimal gap between support and edge of the wheel. Lots of designs for simple supports, many will quote the Harold Hall design.

Neil

[David Clark 13Participant @davidclark13]

Hi there Aluminium oxide wheel as close to A60K5V as you can get. You could go down to 46 grit but I suggest you don't go finer to 80 grit.

[nigel jones 5Participant @nigeljones5]

I use bog standard generic blue wheel just fine for hss. Had same wheel for years.

[Paul NarramoreParticipant @paulnarramore61033]

Thank you all! I have no idea as to the I/D of my existing wheel on my bench grinder but it's very course and took for ever to grind good angles on a lathe tool.

[Paul NarramoreParticipant @paulnarramore61033]

Holy Moses! I've just seen the prices on eBay, not the cost of the actual wheels but the postage from the US. I must look elsewhere.

[Ian S CParticipant @iansc]

Hi Paul, what desert island are you marooned on that you have to import from USA, surely there is a Hardware shop not too far away.

Ian S C

[Neil LickfoldParticipant @neillickfold44316]

HSS will load and dull a good diamond wheel. So when you use it on carbide it will be dull cutting compared to not using hss on the wheel .CBN wheels are much better suited to sharpening hss, but carbide will ruin and dull off a CBN wheel. CBN wheels last a very long time in a commercial environment, so will probably last a lifetime in the home workshop.

Neil

[Paul NarramoreParticipant @paulnarramore61033]

Posted by Ian S C on 29/10/2015 08:55:52:

Hi Paul, what desert island are you marooned on that you have to import from USA, surely there is a Hardware shop not too far away.

Ian S C

Ian, I never said I HAD to import stuff from the US but observed the very high cost of postage. I am restoring a 35yr old motorcycle, the spares of which are like gold dust here, however they are plentiful in the US as they eventually built a factory to assemble Hondas in Ohio. So again, the spares are attractive but the postage is sky high. My local hardware shop doesn't sell Honda GoldWing parts nor aluminium oxide wheels, but I can always ask

Neil, And a CBN wheel is what precisely? TTFN.

 

Edited By Paul Narramore on 29/10/2015 10:47:55

Edited By Paul Narramore on 29/10/2015 10:50:29

Edited By Paul Narramore on 29/10/2015 10:51:14

[hthParticipant @hth]

Hi

I do the roughing out of my HSS lathe tools on a white alox 60 grit grinding wheel , this basically provides me with the tool shape I am looking for .

I then use a fine 1000 grade alox 1/2" square stick to hand sharpen the cutting edge and radius the point .

Finally I use a " Carborundum" brand Silicon Carbide stone to hand hone the cutting edge to a nice sharp edge . I usually dress the SC stone with a fine grade diamond plate .

There really isn't any need to use wheels for the final sharpening work, I feel that hand honing is a better method. Mike

[Neil LickfoldParticipant @neillickfold44316]

CBN are Cubic Boron Nitride wheels. It is either a matrix of the material on a metal wheel, so looks like a desic diamond coated wheel. The other type is a wheel with a compound like a diamond wheel, but the compound is CBN so looks like tire of bonded material,

Neil

[AjohnwParticipant @ajohnw51620]

The main problem with sharpening HSS on a green grit wheel assuming that it is one intended for use on carbide is that it will glaze fairly quickly and then cut more slowly and generate more heat unless its' regularly dressed. As it's intended for carbide which is a harder material than HSS it's less friable. A more friable wheel tends to cut more cleanly so like most things it's a balancing act what ever the material being ground is or the type of grit in the wheel. The more friable a wheel is the quicker it wears away. The less friable it is the more often it needs dressing to expose fresh sharp grit. The ideal degree varies according to the material that is being ground.

Oh how I wish I could remember the grade and hardness of the silicone carbide wheels I used during training. All I know is that it was more friable than what would normally be used for grinding hss tools in a tool room. Done to save having to regularly dress the wheel as rather a lot of tools were sharpened on it, White aluminium oxide only seemed to be used on tool grinders – sharpening milling cutters and re sizing reamers etc with very light cuts.

This highlights an interesting aspect of friable diamond wheel – correct for carbide or for HSS. I'd guess correct of carbide.

John

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[hthParticipant @hth]

These little magnifiers are great for inspecting the edge of your lathe tool .

http://www.ebay.com.au/itm/Mini-50X-LED-Microscope-Jeweler-Magnifier-Glass-Loupe-Currency-Detector-D0X8-/351317064562?hash=item51cc20fb72:g:t3MAAOSw7ThUeBXR

[Roderick JenkinsParticipant @roderickjenkins93242]

Posted by John W1 on 29/10/2015 20:06:59:

The main problem with sharpening HSS on a green grit wheel assuming that it is one intended for use on carbide is that it will glaze fairly quickly and then cut more slowly and generate more heat unless its' regularly dressed. As it's intended for carbide which is a harder material than HSS it's less friable.

My understanding is that the binder of green grit SiC wheels is softer (more friable) than for aluminium oxide wheels. The wheel therefore wears more quickly, thereby exposing new, sharper grains.

Rod

[VicParticipant @vic]

I sharpen HSS tools on a belt sander with a 60 or 80 grit belt. If required I fit a 240 grit belt for a nearly polished finish on the tool.

[AjohnwParticipant @ajohnw51620]

Posted by Roderick Jenkins on 02/11/2015 10:08:32:

Posted by John W1 on 29/10/2015 20:06:59:

The main problem with sharpening HSS on a green grit wheel assuming that it is one intended for use on carbide is that it will glaze fairly quickly and then cut more slowly and generate more heat unless its' regularly dressed. As it's intended for carbide which is a harder material than HSS it's less friable.

My understanding is that the binder of green grit SiC wheels is softer (more friable) than for aluminium oxide wheels. The wheel therefore wears more quickly, thereby exposing new, sharper grains.

Rod

That's contrary to the green grit wheel I have Rod and to what I believe. Wheels are made less friable for grinding harder materials and various grades of hardness are available even in aluminium oxide. As it's not used that often I did try using the green grit wheel to touch up hss and it doesn't work well at all because it was incapable of breaking down the wheel. The wheel is probably over 20 years old now but I'd be surprised if things have changed. The hss wheel is too – regular resharpening with a stone means it doesn't get used very often. That wheel isn't aluminium oxide. Just the usual old style grey stuff which from memory is plain carborundum. It's a long time since I bought one. Both on a Newtool 8" grinder bought from Graham Engineering. No wobble or vibration to speak of, it just sits loose on a bench and the wheels only needed very light dressing from new.

I only went into a 6" wheel and aluminium oxide out of curiosity as some were using them and not too happy about the results they were getting. I found that it was pretty useless with the original woolworth wheels on so fitted Axminster aluminium oxide and found that it's ok, slow but not generating too much heat. It doesn't produce such sharp edges as other wheels I have used though. I'd guess Axminster mostly sell wheels for carbon steel woodworking tools hence the mess they make in use. However they still tend to get black in places due to HSS build up. That may be down to quality.

John

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[Roderick JenkinsParticipant @roderickjenkins93242]

**LINK**

I'm totally confused now, it seems that the friability refers to the break up of the grains themselves rather than the bond, which they seem to refer to as "tier" and has a range of good, better, best etc.. This confirms your comment that the HSS tool was incapable of breaking down the wheel. And, of course, carborundum is SiC.

Rod

[AjohnwParticipant @ajohnw51620]

The term friable doesn't seem to be used much these days Rod. Maybe that's the problem. I'm 100% sure it was used to describe the bond where I come from – the ability for the bond to break down to expose fresh grit. Maybe a miss use. That wheel I mentioned used during training was described as more friable. In other respect the grit grade and type was 100% identical to what Lucas used in tool rooms. Probably for reason of economy. They had even standardised on toilet paper type and size plus hand drying tissues etc that resulted in min cost – Any thinner, lighter, smaller and people just used more. LOL I'm reminded of that when I go to many places and grin when I have to use stacks of it.

I may have an old Graham Engineering catalogue about. It would be interesting to see what type of grit but my recollection is that grey = carborundum. I did use white al ox on a tool grinder. Only for really tiny cuts. Fortunately I was never presented with 1/2 a dust bin full of end mills to sharpen all over, One colleague wasn't so lucky. Having seen that going on it leaves me wondering why people round here just sharpen the ends. If the cutter is blunt it seems like a waste of time to me.

John

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[Mark CParticipant @markc]

Here is some information on wheel selection

**LINK**

These people have a bit of experience about the subject…

Mark

[Roderick JenkinsParticipant @roderickjenkins93242]

Snap!

[Neil WyattModerator @neilwyatt]

This little bit of that document is useful:

Single Point Diamond:
1. Infeed/pass should not exceed .0015" for aluminum oxide abrasives, .001" with Norton
ceramic alumina wheels
2. Dress traverse rate 10"-20" per minute for rough grinding & slower for finish grind
3. Use a 10º-15º drag angle to the wheel centerline
4. Rotate the diamond often to extend tool life
5. Use coolant when possible to extend diamond life

[AjohnwParticipant @ajohnw51620]

I suspect that pdf is well out of date and doesn't relate to off hand tool bit grinding. The industrial catalogue does have a bench / pedestal grinding section but doesn't have much of a selection. It can be found here

**LINK**

Where oh where have the wonderful designations gone ? Replaced by n digit numbers. I had wondered why info on RS was scant – one of the few Norton stockists I am aware of.

No luck finding the catalogue but did find a Reeves 23 edition. On wheels they list green grit and standard grit. On slip stones though they list carborundum for HSS and silicon for carbide. Grey wheel = carborundum just like the stones. There choice of slip stone surprises me the best were india stone, a reddy brown fine natural source of al ox.

I had a giggle when I saw that the new Reeves intended to stock as much as the old one.

John

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