How best to sharpen Carbide tools

Sunday, February 6, 2011

Follow the lead of the guys in machine shops and use Silicone Carbide bench grinder wheels

by KEITH BERGLIND

Carbide bits and tools can be a bit of an annoyance for most of us ordinary home shop guys. Most of the time, when you try to sharpen a saw blade or lathe tool bit on the regular grindstone, it turns out badly or remains dull.

Regular grinder wheels just don't work. Many lathe bits get thrown to the back of the tool box: dull and useless. I have exchanged more than one table-saw blade because the blade had chewed its way through one-too-many nails.

But the guys in the machine shops have a better solution: – they use Silicone Carbide bench grinder wheels. These wheels look quite like ordinary grinder wheels at a quick glance, typically six- or eight-inch diameter, one-inch wide and 80-grit coarseness. But the colour is slightly different. I didn't do a store survey of current products, but I remember the green wheel we kept in our shop. It was mounted in the grinder only when needed to sharpen a carbide tip.

For this article, I purchased a "green" wheel, which is noticeably different from a regular grinder wheel, but in a busy shop it could easily get used by mistake. And they cost about three times as much, so you don't want to see it wasted.

It is important to note that these wheels are "softer" than the normal grinder wheels and are not intended for daily use. They cost more and wear out faster.

The problem now is that you can't buy these at most general tool stores. I'm too far from a Home Depot for price checking, but I am close to a very large Princess Auto store, so that's a logical place to start. Product shopping here always starts with the Princess Auto catalogue, which lists these wheels as SI-Silicone Carbide abrasive for harder material, such as carbide tipped cutting tools.

I have a friend who sells Norton abrasive materials, so I bought a wheel from him for just over $30.

You will quickly learn that these wheels wear quickly, so be sure to use the right grinding pressure against the wheel and use the full face of the stone to prevent grooves from developing.

I've never tried to straighten up one of these stones with a diamond, as I do often with regular grinder wheels. Since the carbide bit sharpening we do is free hand, it is easy to use the full face of the stone.

I know few guys need one of these stones, but when you have all the ordinary tools that your friends have, here's a special item just for you. BF

Keith Berglind is a licensed heavy-duty mechanic.