Sharpening carbide with diamond wheel

[Vern Smith]

I want to sharpen some carbide drills. I know the green wheels work but I was wondering how a diamond wheel works on carbide? Specifically, I would like to use my Drill Doctor which has a diamond wheel. I realize it's not the best or most precision way to go but it would be better than I would do by hand on the green wheel.

Vern

[MadMax]

I've done a little hand grinding on carbide with diamond wheels. It seems that most wheels are too coarse to make a nice factory quality edge. Under microscope the edges tend to be fairly chippy and not very durable as a consequence (too many crack starts). I suspect that carbide is professionally finshed with very fine abrasives. You can get away with some hand grinding, but you won't get a very durable edge. It is handy for making quick lathe form tools though.

Do wear respiratory protection when grinding carbide. The grinder dust has particularly bad respiratory issues. I do any of my heavy grinding (say cutting a 3/4" boring bar shorter) outside wearing a respirator. I protect myself with the respirator and try to keep the workshop clear of the grinder dust because it's terrible abrasive stuff that you really don't want floating around.

[HuFlungDung]

I've done some hand grinding of carbide with natural diamond wheels. But I use a 6" bench grinder, using the same technique as I would use for grinding HSS drills. Shars Tool offers diamond wheels on a budget, and I find no problem with using them. I would recommend making an integral rear flange/bushing combo to adapt the wheel to the motor shaft, rather than relying on the crappy little flanges that come with cheap bench grinders. A true running flange will make a true running wheel, and it should not 'bang' your carbide enough to damage it. I like about 100 grit. It cuts carbide easily without leaning hard on it, or dwelling indeterminantly while you wait for it to wear its way across the face, such as green wheels do.

I only use a green wheel for backing off the steel support under brazed on carbides. I usually grind a little excessive secondary clearance across the tool, the go to the diamond for actually sharpening the primary clearance angle, which supports the cutting edge.

As for using your Drill Doctor, I do not know about that, but I understand that they only have a small diameter wheel in them, and if they are CBN, then it may not seem so sharp next time when you go to grind HSS with it.

[rusty abe]

I agree with you, vern. Regardless the quality of tool grinder, it gives far predictable result than using free hand grinding. I use Darex drill grinder for my drill bits grinding. Though I still have a lot to learn to better use my darex.

rusty abe