I have a question about brad point bits. I have one of the 7mm Fisch pen drill bits from Woodcraft. I plan on drilling on the lathe. Anyone see any problems with the long bit as drifting, etc. Alternate source for metric bits?
All of my metric bits are bradpoint. So far, I have not noticed any drift when drilling on the lathe. I have noticed that my holes are slightly angled when drilling on the press...the exit hole is sometimes shifted by half a millimeter to a little over a millimeter. I think it has to do with the angle of my table, and the flatness of my pen blank self-centering vise. I don't think they are entirely flat. I've taken to leveling the vise every time I drill a set of blanks, and I can get it pretty close. But I don't think the issue with exit hole misalignment, when it happens, is so much wander as the angle issue...because, if I drill a set of blanks one after the other, every single exit hole is off by the same amount in the same direction. If it was wander, I'd expect the exit holes to be more randomly distributed...
On the lathe, I seem to get pretty darn strait holes every time...it just takes significantly longer to drill on the lathe. With bradpoint bits, I make sure to give the point some time to make its hole, and make it good, before I let the outer edges of the bit start cutting. Note that, a bradpoint actually cuts at the center and at the edge simultaneously...and for the most part, the point in the center protrudes only slightly more than the points at the edge... Given that, I'm not sure how much wander is truly possible, unless you are really DRIVING the bit in with a lot of force? I tend to keep the pressure light, and let the tool cut and do the work on its own, as much as I can, and I frequently back out to clear the flutes (especially as you get deeper).
Anyway...I actually like bradpoints for some of the more challenging materials. I have more trouble with standard bits on materials like trustone (or its counterparts, as there are a few cheaper alternatives on the market now). Bradpoints, the way they cut at the outer edge, actually seem to exit really nicely and without any chipout, without cracking blanks, like I've seen with standard bits. Trustone is often very fragile and powdery, and I seem to need more force to drill those with a standard bit, and that extra force...it is just higher risk I guess.
I DO use standard bits on wood. I like em, they seem to do an excellent job. I use the cobalt bits I mentioned earlier in the thread, and they cut exceptionally well. In all honesty, I'm not sure if the standard bits drill quite as dead centered as the bradpoints? Even on the lathe, sometimes it seems the hole might be slightly (very slightly...hard to tell) off centered...but, I think its actually more due to how the bit contacts, and how much it flexes on contact, than wander or anything like that. Smaller bits, seem to have more flex (i.e. 3/8").
