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Dan from PA
07-21-2000 15:45:23
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Re: Drill Bits in reply to F14 , 07-21-2000 09:19:55
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I had a fellow show me once how to sharpen drill bits. It was the best 10 min I ever spent. I had one of those sharpening attachments for the bench grinder, but I've never talked to anyone who's been able to get one to work right. This guy did it freehand. He had a little flat metal gauge that kind of looked like a "Z" (I've seen them at Sears) to check his work as he went along. I was going to get one, but I've had acceptable results without it, so I never did. I'm sure my bits make egg-shaped holes, and they probably don't drill straight, but they put holes in metal. :)
Here's how, using a bench grinder:
First, put on a face shield.
Then, make sure your wheel has a flat face. Get one of those stone dressing tools. In a pinch, you can hold a piece of cinder block or a Pennsylvania Potato (rock) against the wheel. Move side-to-side to get a flat surface. Be careful! This is a great way to hurt the fingers.
Next, stand in front of the wheel like as if it were a car tire you'd be about to get run over. Hold the drill bit with both hands in front of you so the shank end is close to your sternum, the point is away from you, and the bit is almost horizontal, with the point pointing slightly uphill. Now, kick the shank end to the left (for standard right-hand-cutting drills) to get whatever angle you want the drill bit to have (I think 110 deg is pretty all-purpose, so you want to move the shank to the left about 35 deg). Rotate the drill until there is a cutting edge pointing straight out to the left. Touch this edge to the center of the wheel, level with the grinder's shaft. You want the cutting edge to be in contact with the wheel all along its edge. Practice with the power off to get a feel for it.
Now, just push the bit straight up, following the curvature of the wheel for a ways. This gives you the heel angle. You may need to play with how far from horizontal to hold the drill to get this right. Too close to horizontal, and the bit won't cut. Too far, and the bit may try to cut too fast, or dull too quickly, or the edge will chip.
Use light pressure, and only take 2 or 3 cuts on one side before turning the drill over to do the other side. Have a cup of water handy and swizzle the drill around in it often. Keeping the bit cool is the key. Take your time. Look at the end of the drill and keep the webbing centered between the edges. This is what the gauge was for.
This has saved me *so* much money buying new drills, and aggrevation fighting dull ones. Even broken drills can be rejuvinated if they're not broken too close to the shank (the webbing gets wider there). Don't be afraid to re-sharpen if the bit doesn't seem to be cutting or if it starts squealing. You'll soon get the hang of it. There's now a lovely pile of long curly cuttings under my drill press, instead of the tiny chips I used to get. And the drills seem to melt through the work. I've even drilled leaf springs and brush hog blades.
Since I learned to do this, I've had a love/hate relationship with those new spilt-point bits. They're nice when they're new, they cut well, they're strong, and sometimes you don't need to center-punch, but you can't sharpen them with this method; the webbing is much wider than standard bits. Regular drills are actually getting harder to find.
Give it a try before you spring for a new set!
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