You're probably right about the optimism thing. I've never been accused of being either wildly or blindly optimistic, so I'll probably have to consider two-step in-the-piano drilling. Dang. Ron Nossaman wrote: > >> There must be something subtle happening right at the cutting edge of >> the drill where tiny variations in sharpening / grinding make >> noticeable differences in hole size, or maybe surface texture inside >> the hole. I've been using a Woodcraft fast spiral brad point 17/64 >> in delignit. The first one I bought gave me 120 in-lb with 1/0 >> pins. Thinking I'd discovered the holy grail, I went out and bought >> a half-dozen more bits. They all mic the same (.267) but each gives >> a different pin torque. Except for that first bit, none have given >> me a tight enough fit on a 1/0 pin. Is a puzzlement. >> >> Mike > > I've always freehand sharpened jobber bits when I managed to damage > the cutting edges. I've learned from this that it doesn't take much of > an off center point to make the hole oversized. I've also learned > that double drilling brings final size accuracy back into range when > you need close tolerance accuracy, even with hand ground angles and > centering. Trying to drill 0.009" undersize in one pass in Delignit > with a brad point bit and getting a uniform (much less a medium torque > level) fit strikes me as wildly optimistic. > > Ron N >
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