Thread: Carbide Tip Sharpening

On a grinder with the correct wheel.

Are you talking about replaceable tipped tools or brazed on tips?

Generally you need a "green" or diamond wheel to grind anything this hard. However, if your referring to replaceable tips....why would you try to sharpen them?

Thanks Chief, they are the Brazed type.

Originally Posted by Chief Tiff

However, if your referring to replaceable tips....why would you try to sharpen them?

after you brazed them to a bit of steel for new turning tools...or so ive been told

No worries. You need a silicon carbide grinding wheel (a "green" wheel) in a bench grinder, take gentle cuts with no lubricant or quenching. You can also hone the tips with fine diamond files between sharpenings.

Originally Posted by eskimo

after you brazed them to a bit of steel for new turning tools...or so ive been told

Hmmm.... never actually thought of doing that! Then again, I absolutely hate having to grind tools and have always tried to use a TCT every time.

I've turned chipped tips into negative rake tools for roughing out harder materials but generally I just chuck 'em away once they're unserviceable.

A diamond wheel with the diamond particles embedded in phenolic resin cuts fast and is pretty cheap these days from the Internet. The only thing you have to watch out for is avoiding contact with the steel base of the tool and the diamond, as the steel will ruin the diamond, something to do with the carbon content of the steel and the carbon of the diamond crystal. It will need some form of lubrication too like water or kero or wd spray.

If you undercut the steel below the carbide piece with a conventional grinder wheel you can then grind the carbide on the diamond wheel without damaging it. I tend to go with 100 grit 100mm dia cup wheels as I picked up a few for $15, on the 'net. Plated diamond wheels are also cheap and worth considering too. I have 250mm silicon carbide wheel but I've yet to get it running on a spindle so i can't comment on it, i have heard it's a lot slower than diamond though and the wheel does wear quickly as it's designed to do.

Does anyone know whether using a CBN wheel to touch up brazed carbide tooling would harm the wheel? I only have 4 brazed carbide tools (from a face mill which originally came with a mill drill) so have never bothered to get a green wheel, and the tool hasn't been used for years. The CBN is so easy and quick making and sharpening HSS tools that I would hate to damage it by grinding brazed tungsen if it is not suitable for this purpose. I have not been able to find any references on the internet which give this information.

Frank.

Frank,
what shape & grit of CBN wheel do you use for your HSS tools?
Chris

Originally Posted by jack620

Frank,
what shape & grit of CBN wheel do you use for your HSS tools?
Chris

Hi Chris,

I have the 150 x 20 wheel described here:

http://cws.au.com/shop/category/opti...rinding-wheels

Sorry, I can't remember the grit, and it does not seem to appear in the wheel description in the seller's literature. It is very fast cutting though, but leaves a much nicer finish than the old grey wheels.

Frank.

I had a look at the Norton Abrasives website; in their toolroom selection they list diamond and CBN wheels. They state that CBN is second only to diamond in hardness and under the descriptions of each type they list typical uses. They recommend diamond for off-hand grinding of brazed carbides and CBN for HSS and alloy steels.

Maybe try to sharpen one of your cutters on an unused part of the CBN wheel and see how it affects the wheel, but if CBN is really that hard I can't see any potential issues.


(note: It's great to be able to offer advice knowing full well it's not my gear being experimented on )

Thanks Frank. Pity their thinnest wheel is 20mm. My little grinder only takes 13mm wheels.

I've been considering something like this:

eBay Australia: Buy new & used fashion, electronics & home d

Your wheel appears to be CBN bonded to steel. The one I linked is diamond embedded in resin. I've also seen CBN in resin. It's bewildering the variety of wheel shapes, abrasives (alox, diamond, CBN), bonds (metal, resin), grits, abrasive concentrations, etc. Makes it hard to choose the right wheel. And then I wonder about the quality of a $30 wheel.

Chris

Chief Tiff,

Thanks for checkiing on the Norton site for the information on using CBN on brazed tungsten. I have not yet found an authoritative source which specifically recommends CBN wheels for the purpose.

In view of that, and your vote of confidence in the information, (which mirrors my own misgivings!)

It's great to be able to offer advice knowing full well it's not my gear being experimented on

and the cost of a replacement wheel, I think it would be more sensible to get a couple of sticks of 3/8" square HSS and make a new set of cutters from this if I need to use the tool in future.

Regards,

Frank.

This is basically all you need. Not expensive.

6" SILICON CARBIDE GRINDING WHEEL / HSS GRINDING WHEEL | eBay

I've been regrinding carbide cutters for use with this type of wheel for years.

It's easy to bronze braze carbide onto DIY boring bars and the like, and grind the cutting facets freehand.

Save yourself a fortune. You lose the indexing function, but so what?

If done correctly you can achieve a razor sharp edge on carbide.

I'm currently using a Norton grey diamond wheel (nearly worn out) that was rescued from a valve facing unit.

HSS is OK for easy machining jobs, but try it on high carbon metal/weld and see how it (doesn't) perform

Rob