drilling in the center

[aggromere]

I drill on the lathe. I round my blanks to cylinders before drilling and make sure they are centered in my chuck. I center drill the blank about 1/2 inch or so with a small center drill. Then I switch that out with the bit I am going to use for the pen. 90% of the time it comes out just fine. However, once in a while it seems something forces the bit to the side slightly and the exit hole is not on center, so I essentially drilled at an angle through the blank. Happens on longer blanks I drill, most of which are closed end so I don't really know the hole is angled till I chuck it up on a closed end mandrel and collet chuck. Questions I have:

1. Could it be a hard spot or soft spot in the wood causing it? If I drilled to whatever depth I am going with a smaller bit first, would that eliminate it. I use both the regular bits and the brad points, which doesn't seem to affect it either way. Anyway, any suggestions to minimize this or do others have the same problem on an occassional blank?

I started thinking through all that I do to make pen and theoretically it is very simple. However, in reality, the execution of the simpliest of things can be difficult, at least for me.

Just looking for feedback.

 

[hasha2000]

While at a demo at Woodcraft, the instructor talked about pilot holes on soft wood, burls, and acrylics. Makes sense to me.

 

[sbwertz]

I was having trouble with off center drilling on my drill press with a self centering vise. I discovered that I was running the drill press at too slow a speed. (I had it at its slowest speed).

I increased the speed to the middle pulley and it drills straight through the blanks now.

 

[Russianwolf]

several things can cause deflection when drilling. I've had it happen many times when drilling blanks cut on a bias, since the grain lines aren't running parallel to the bit, it wants to follow where they go. So it can be an effect.

I have found that drilling the hole with several steps (1/8in, 1/4in, then final size) helps tremendously. Also make sure your bits are very sharp.

 

[ldb2000]

A number of different things can contribute to a hole drilling off center . The number 1 cause is the grain of the wood causing the drill bit to deflect .
Other causes are dull drill bits requiring more pressure to advance the bit and causing the bit to flex and go off center , bent drill bits that start to wonder and go off center , thin bits like a 7mm are more easily deflected or flexed and are more likely to go off center , long bits are also more likely to flex and go off center . Any one of these things can cause the problem but it's usually a combination of these things that that are the cause .

 

[PenMan1]

Generally speaking, when I drill on the lathe and the hole "wanders", nine times out of ten it is because of a knot, soft spot, weird grain pattern, etc. That tenth time, it is because I forgot to roll my screw machine bit across a flat surface to make sure it hasn't been damaged.

Respectfully submitted.