Need Help Sharpening Carbide Lathe Bits

[SG51Buss]

About a dozen years ago I bought a glom of budget 1/4" braised carbide bits, and the set of braised carbide boring bits. They were all dull, and had goofy angled convex faces. My existing carbide bits needed dressing, and these new ones were supposed to solve that.

Fast forward a few years, I find these 2" diameter diamond disc-wheels on eBay, pack of 10 for about $20, if I recall correctly. Recommended rpm of 3000.

There's a few articles on small homebuilt sharpening stations out there for inspiration. So, made a dc motorized sharpening station. Modified a stainless steel protractor as a sliding mitre base. No heat or severe loads here, so made it out of wood.

Didn't want to do the complicated tilting mitre table thing, so this mitre table stays flat, the motor/disc assembly tilts to the desired angle. Normally leave it at 8° back tilt. Can freehand on it too, handy for those boring bar bits.

It rapidly removes carbide, leaves an almost-fine finish. Works well on HSS too.

 

[SmokeWalker]

I have a grinder with a small adjustable tilt table in front of a cup wheel, so I don't get a hollow grind but that's OK as I think carbide doesn't need to have too thin a cutting edge.

Bernard

Sorry but I've no idea what grit it is as it was an unmarked freebee...so I have no experience of other makers wheels.

But I do like the much reduced dust while using the diamond wheel.

Bernard

Thanks for the tips. I'm still worried that if I get this McMaster grinding wheel it might not work for freehand stuff. (Honeycomb appearance)

How must are planning to grinded carbide
I use mostly HS so if do a carbide or two time I use the standard wheel
I have gone down the road with carbide grinder and wheels.
I do a lot of grinding with a Home Depot wheel and it is cheap.

Dave

Dave, if I understand correctly, you grind carbide occasionally on the standard wheel? (Concrete? Al2O3?)

About a dozen years ago I bought a glom of budget 1/4" braised carbide bits, and the set of braised carbide boring bits. They were all dull, and had goofy angled convex faces. My existing carbide bits needed dressing, and these new ones were supposed to solve that.

Fast forward a few years, I find these 2" diameter diamond disc-wheels on eBay, pack of 10 for about $20, if I recall correctly. Recommended rpm of 3000.

There's a few articles on small homebuilt sharpening stations out there for inspiration. So, made a dc motorized sharpening station. Modified a stainless steel protractor as a sliding mitre base. No heat or severe loads here, so made it out of wood.

Didn't want to do the complicated tilting mitre table thing, so this mitre table stays flat, the motor/disc assembly tilts to the desired angle. Normally leave it at 8° back tilt. Can freehand on it too, handy for those boring bar bits.

It rapidly removes carbide, leaves an almost-fine finish. Works well on HSS too.

Thank you. Gorgeous work and that sounds like a terrific idea! What did you search for on eBay to find those diamond wheels?

 

[SG51Buss]

I did a search on: "diamond cut off wheel" and 90 items popped-up.

Hope the links work, here's the 2" wheels:

Item: 10pc 50mm MINI Diamond Cutting Discs Fit Rotary Tool Dremel Drills Cut Off

URL: http://pages.ebay.com/link/?nav=item.view&id=321423773446&alt=web

Alt URL: http://www.ebay.com/itm/10pc-50mm-M...tary-Tool-Dremel-Drills-Cut-Off-/321423773446

Back then, communicating with the seller (supplier to asian tooling industry), he stressed the importance of keeping the speed down to 3000 rpm, even recommending a water spray. I've used them at 3000 rpm DRY quite successfully. Don't need any backing plate, very little contact pressure is all you need...

 

[Karl_T]

I've used brazed carbide lathe tools for 25 years now. Like you've discovered, carbide is hard to sharpen. One thing you may not know yet, diamond wheels are quickly eat up by grinding any steel, like the steel supporting the brazed carbide.

This is probably too high a cost solution, but it does work extremely well. First get a baldor type tool bit grinder. Put a green wheel on the left and set it at the secondary relief angle, 12 degrees IIRC. Then put a diamond wheel on the right and set it to the primary relief angle, 6 degrees IIRC.

OK, most of the material removal is done on the green wheel, left side, because its cheap to replace. Then the final cut to get the tool super sharp is done on the diamond, right side.

Carbide lathe tooling produced this way is superior to carbide inserts in many ways. In particular, the problem of carbide needing a deep cut to work well is eliminated.

 

[GarageGuy]

I use a cheap Harbor Freight 4 1/2" diamond wheel ($10) in a 5" bench grinder to touch up chipped tips on my cemented carbide cutting tools. I've never tried using it to grind a profile, only to fix chips or smooth damaged straight edges. It would be a cheap enough experiment though. The most you could lose is a $10 HF diamond wheel.



GG

 

[george wilson]

Use cheap Chinese diamond wheels. And,carbide does NOT need to be hollow ground. It would only weaken the cutting edge and cause it to soon break off.

 

[jgedde]

Hello Everyone,

I need to resharpen some tool bits as discussed above to the same or close to the same kind of sharpness I can get with HSS.

I can grind HSS on my HF 39797 grinder with included wheels no problem, but when I try to grind HSS on the new Silicon Carbide wheels, it's slow, and very…finicky. It's hard to remove enough material to get a nice hollow ground edge.

I'm trying to get the same kind of hollow ground on my carbide bits with the Silicon Carbide wheels (60 and 150) but though I can tell by using a marker on the surface that the grinder is removing material, I can't seem to get the shape I want.

Do I need to practice more?

Also, I am thinking about getting a Diamond wheel like this:
http://www.mcmaster.com/#diamond-grinding-wheels/=uvqnqb

And I'm wondering if that would work for my purpose. I've heard that you shouldn't grind freehand with a diamond wheel because it takes off too much material. That might be what I need. I have steady hands, but I'm wondering where to go next.

Any thoughts?

Pierre

On my HF tool grinder, I threw away the wheels the grinder came with (they're junk). I replaced one with a white aluminum oxide wheel for HSS. The other was replaced with a 100% concentration resinoid diamond wheel for carbide. It works VERY well and get's carbide mirror smooth and razor sharp. I can also use the edge of the wheel to grind special forms, chip breakers. I even use the diamond wheel to touch up spent carbide inserts I get from work. Makes them work like new again.

For carbide, the silicon carbide wheels are really only good for roughing. You need a diamond wheel to get 'em HSS sharp. When you buy a diamond wheel, get the white dressing sticks too. The dressing sticks are very inexpensive. Enco carries them.

John

 

[SmokeWalker]

I use a cheap Harbor Freight 4 1/2" diamond wheel ($10) in a 5" bench grinder to touch up chipped tips on my cemented carbide cutting tools. I've never tried using it to grind a profile, only to fix chips or smooth damaged straight edges. It would be a cheap enough experiment though. The most you could lose is a $10 HF diamond wheel.

View attachment 89077View attachment 89078

GG

That looks pretty interesting, but assuming I could get to the side of the wheel (I can make a stand) how much pressure do you think I could apply to the side? It's diamonds embedded in steel plate, yes?

Use cheap Chinese diamond wheels. And,carbide does NOT need to be hollow ground. It would only weaken the cutting edge and cause it to soon break off.

Thanks for the tip. Yesterday I was actually trying to put a hollow ground on the top of the tool. (Inexperienced me.) It wasn't until a machinist friend came by and pointed out that the carbide is brazed on an angle to the holder, so I already had clearance.

On my HF tool grinder, I threw away the wheels the grinder came with (they're junk). I replaced one with a white aluminum oxide wheel for HSS. The other was replaced with a 100% concentration resinoid diamond wheel for carbide. It works VERY well and get's carbide mirror smooth and razor sharp. I can also use the edge of the wheel to grind special forms, chip breakers. I even use the diamond wheel to touch up spent carbide inserts I get from work. Makes them work like new again.

For carbide, the silicon carbide wheels are really only good for roughing. You need a diamond wheel to get 'em HSS sharp. When you buy a diamond wheel, get the white dressing sticks too. The dressing sticks are very inexpensive. Enco carries them.

John

Hey John, what is your source for a "100% concentration resinoid diamond wheel". I like the way you're talking. What grit did you use for the white wheel? 150?

Pierre

 

[Bill C.]

Hello Everyone,

I need to resharpen some tool bits as discussed above to the same or close to the same kind of sharpness I can get with HSS.

I can grind HSS on my HF 39797 grinder with included wheels no problem, but when I try to grind HSS on the new Silicon Carbide wheels, it's slow, and very…finicky. It's hard to remove enough material to get a nice hollow ground edge.

I'm trying to get the same kind of hollow ground on my carbide bits with the Silicon Carbide wheels (60 and 150) but though I can tell by using a marker on the surface that the grinder is removing material, I can't seem to get the shape I want.

Do I need to practice more?

Also, I am thinking about getting a Diamond wheel like this:
http://www.mcmaster.com/#diamond-grinding-wheels/=uvqnqb

And I'm wondering if that would work for my purpose. I've heard that you shouldn't grind freehand with a diamond wheel because it takes off too much material. That might be what I need. I have steady hands, but I'm wondering where to go next.

Any thoughts?

Pierre

I always tried to grind carbide using the tool support to maintain the same clearance angle. I think the angle is about 5 degrees. I also use a general purpose wheel to grind relief of the HRS stock below the carbide. I have used them until there was just a little chip of carbide left. I remember each wheel only cuts the material it is designed to grind otherwise the tool bit starts getting hot to hold. Hope this helps.

 

[Reeltor]

Some interesting ideas on grinding carbide. On brazed carbide bits, I use a set of HF diamond sharpening stones/plates; what ever you want to call them. I'm not trying to change the shape of the carbide just hone the edge to be nice and sharp. Seems to work.

Mike