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I'm new to turning and recently decided to make some pepper mills. Starting with squareish stock I roughed the pieces to round and then started drilling several concentric holes of different sizes using forstner bits on the lathe. Somebody gave me the feedback that I should use the largest drill bit first and not to drill any pilot holes. In other words if I need a 1.5" through hole and a 2.5" hole at 1" depth then I should drill the 2.5" hole first followed by the 1.5" hole. This flies in the face of everything I've been taught, but the explanation was that the forstner bits do better without large pilot hole (e.g. from another forstner bit).

In any event I was able to drill the holes into the work pieces, but as I did this I noticed that the drill bit appeared to be wobbling rather substantially (it looked like the work piece was "pulling" the bit such that it wasn't always inline with the axis of rotation. I assume that this is because the drill bit didn't enter the piece perfectly inline with the axis of rotation though for the first ~1.5" I couldn't tell and it looked good). This was especially true when I used a drill bit extension to get the depth I needed (I started swapping in the extension only when I needed it rather than starting with it for deeper holes).

After I drilled the holes I used a cone/chuck to hold the piece in place for sanding/finishing. On several pieces I noticed that the through holes were not concentric with the outer surface of the work piece. In other words when I'd pull the spindle off the lathe I'd notice that the through hole appeared to be at a slight angle relative to the outer surface.

What's the best way to drill a hole that is "perfectly" concentric with the outer surface of a work piece on a lathe? Is it better to drill first and then rough/round? Should I in fact be using a pilot hole? Am I not securing the piece in the chuck properly prior to drilling?

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  • I havd no turning experience, but my instinctive reaction is: Drill out the core, then mount the piece betwedn cones and shape the outside to match that centering, rather than the order you tried...? – keshlam Dec 21 '15 at 22:15
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    The other cheat: Drill from both ends. If the middle is not a perfect mstch, nobody will notice or care. – keshlam Dec 22 '15 at 0:12
  • Is the bit wobbling or is it the wood? If you are not chucking the wood at the head stock and just using a spur center, it's going to be extremely difficult to keep the wood from wobbling. – Ast Pace Dec 22 '15 at 1:53
  • @ASTPace I am chucking the wood and the bit itself is wobbling. – Doov Dec 22 '15 at 17:44
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I assume you are talking about using a wood turning lathe and you have mounted the work on the headstock and have the bit mounted in the tailstock. Getting everything lined up on a wood turning lathe will be difficult. They are not made for boring.

I would recommend using a drill press instead.

If you are making through holes there is no reason to be using a Forstner bit. Those are used for making blind holes.

There are various YouTube guides on how to do boring on a wood turning lathe:

https://www.youtube.com/watch?v=NCrETz4RTyM
https://www.youtube.com/watch?v=l24q7r_sg2A
https://www.youtube.com/watch?v=F3fueO0oP80

The last of these is actually on boring a pepper mill, your exact problem.

If I was making a lot of pepper mills, I would probably make a setup with a cutting mandrel. First a hole is drilled through the blank using a drill press. Then the mandrel is threaded through this hole and tightened with a collet to the chuck. A v-block fixture is used to support the work at specific height. Then the work is pushed along the mandrel to cut the holes. The mandrel has two cutters mounted on it, so that the entire inner diameter of the worker will be cut in one step. This kind of setup is somewhat advanced, but if you are making a lot of pepper mills would be desirable because it will be fast. The mandrel is very rigid. For example, if you watch the 3rd video above you can see how he has to keep backing out the drill. A mandrel cutter is really powerful and will just bore the whole thing in one move.

In any case you would turn the outside of the pepper mill after doing the inside, so the outside should always be concentric with the inside.

  • This is a great suggestion, even if I could +1 my own answer, this one get's my support. Great thought. – BrownRedHawk Dec 22 '15 at 17:30
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This is a very tricky thing without a VERY stout bit and tailstock. If I 'cheat' (not really cheating IMO) and use a drillbit, I generally finish with a bowl/hollowing tool, which I can get very uniform wall thickness, and a centered hole through to the other end.

The difficulty is in drilling, once the bit is off-center even as little as half a degree, the drilled hole will guide the bit further off course since the flutes do little to any cutting.

Another thought coming to mind would say use a Forstner bit, which does it's cutting a bit differently, and a wire bit support to help guide and support the bit.

Might be worth a shot.

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You need a gun drill for your pilot hole. Drill bit extensions do not work well for making very straight holes, but if the pilot hole is straight enough it might work out.

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