Spontaneous expansion of seasoned hardwood

In your OP, I picked up in the fact that the dowels were getting progressively harder to insert. Were you inserting the dowels in the same order in which you drilled the holes? If so, that suggests that the holes were getting smaller as you went. Is it possible that the wood was contaminated (someone has already mentioned silica) with something like salt that caused excessive wear on the bit?

Another thing came to mind; try increasing the speed of the drill and the feed rate. If you compare the hole with one drilled at a slower speed and feed rate you may find that the faster one will not produce the effect you are experiencing. Just a thought.

Well, the general advice with hardwoods is that you get a cleaner hole with a slower bit speed. With softwoods, it’s the reverse.

For what it’s worth, I don’t think what Mangetout has is lauan.

I would agree. I have done several projects using lauan, and I always have problems saying the word, as does the man behind the counter.

Yeah, I guess I was assuming it was a softwood. I also don’t think he has Lauan.
I have heard it pronounced as “loo-on” or “lou-on”.

I have a hardwood cherrywood floor and it looks remarkably like this - when hubby was cutting the ends, there are actual burn marks 'cause the blade got so hot.

Interesting idea, but I don’t think so. The dowels were inserted in approximately the same order as the holes were drilled, but for the drill bit to have worn so severely across only 42 drilled holes would be something I couldn’t possibly fail to notice. Not to mention that I used the same drill bit to redrill the holes to the right size.

I think the heating of the drill bit was caused by the wood tightening on it as it went through - the drill was and is still quite respectably sharp. The inside surfaces of the hole are polished smooth because of the tight drilling.

I’m going to see if I can get around to running that test one evening this week.