Hi guys,

I picked up some vintage Union Twist bits with tapered, square shanks. They fit quite nicely in a small 6" brace that has a square chuck with a retention screw -- I've become quite fond of this lightweight little brace for drilling pilot holes, counter sinking, and driving screws. Light weight, handy, and quick to change bits.

Anyway, the twist bits are sharpened at a very obtuse angle meant for metal. As such, they require a *lot* of downwards force to drill into wood, especially the larger diameter ones. This has always been the case with twist bits sharpened at obtuse angles, even relatively new and sharp ones. These might also benefit from being sharpened, though they are reasonably sharp still.

I've never sharpened twist bits, and the info I come up with online is unsatisfactory at best.

My questions are basically:

1. Is there supposed to be a relief angle behind the cutting edge, IE, meaning, that the tip should not be perfectly canonical in shape, but rather a little more steel should be removed behind each cutting face to make sure that the cutting edge, and not the bevel, is in contact with the wood?

2. At what angle would you sharpen these for wood? 30 degrees? I understand that obtuse angles are used for metal, I guess for durability, but if I also wanted to, just occasionally, drill metal, but mostly wood, would some compromise angle, like say 40-45 degrees, be advisable?

I'm guessing I should just chuck them in an egg beater drill somehow so I can spin them (maybe make a wooden adaptor)... or maybe some kind of jig that holds them steady while I spin them with a brace, like a hole drilled in a piece of wood at the desired angle and stuck in a vice, while I spin them on a stone or abrasive paper to get the desired angle, and then I can come back with a small diamond stone and relieve the metal behind the cutting edge (the would be "bevel") a degree or so if necessary. Am I thinking right here?