Question about end grain drilling

[Doug Herzberg]

I turned a knife handle recently. The shank of the knife blade was a perfect cylinder, so I selected the proper size drill bit, drilled a piece of scrap and tested the fit. It was perfect - snug, but enough room for some CA glue. I drilled the turning blank with the same drill bit, but did not test the fit. After turning and finishing the handle, I found the hole was too small. I cleaned the bore out with the original drill bit, but still it didn't fit. Long story short, I had to ream out the hole with the next two drill sizes to get the same perfect fit I originally (and still) had in the test piece. Nearly ruined the turning.

This is a complete mystery to me. The test bore was in a scrap of cottonwood and the turning was Osage orange, but that is the only difference. Both bores were into end grain and done on a drill press with the blank securely mounted in a vice. The wood was dry. Obviously I should have tested the fit in the actual turning blank, but it just didn't occur to me.

Anyone else have such an experience? Any ideas as to cause? I have to be missing something.

[Harold Poland]

perhaps on the harder wood the drill bit wondered slightly making the hole seem tighter. I have had this happen with pen blanks on occasion. I drill on the lathe now for the most part and haven't noticed the problem as much

[David E Keller]

The only thing I can imagine is that the softer cottonwood allowed the bit to wallow out a larger hole while the bois d'arc wouldn't allow it. If I had the same problem, I would just assume that I had used the wrong bit(been there, got the shirt and everything).