Round holes in square pegs - Woodworking Talk - Woodworkers Forum
 
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post #1 of 5 Old 12-19-2010, 02:45 PM Thread Starter
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Round holes in square pegs

Before anyonw hollers at me for putting this in the wrong place: it's here because it has to do with prep work for pen turning.

Drilling holes in those pesky 3/4" x 3/4" pen banks is proving to be very difficult. One end of the blank will be a good fit for the tube, but the other end ends up waller'd out, sometimes in an oval shape.
  • The offending end is the top/start of the hole.
  • Drill bits are brad point and/or standard twist bits.
  • Vice is a Rockler pen blank vice designed for drilling these pesky holes.
  • The vice is permanently mounted to a hardwood base with no twists, kinks; it is flat.
  • The base is drilled so threaded studs can be used to hold the vice to the drill table to keep it from moving while drilling.
  • Drill press table has been checked to verify it is perpendicular to the the quill.
  • I don't have a dial indicator to check run out , but there is no visible wobble at the bit tip.
  • Using same vice on a second drill press produces same results.
  • Swapped bits to no avail.
What is the problable cause and resolution?

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post #2 of 5 Old 12-19-2010, 04:20 PM
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Is the elongation along the axis that the vise squeezes?

I'm wondering ... if one overtightens the vise, as the drill bores through the blank the pressure might squeeze the side-walls of the hole against the spinning bit. End result could be -- when the pressure is released -- a hole that's oval at the top, becoming a more true circle towards the bottom.

How tight do you clamp the vise?

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post #3 of 5 Old 12-20-2010, 02:21 AM
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What is the throw of the press? We have a small bench top press and it has a throw short enough that we have to raise the piece after the quill bottoms out. When we bottom out we then have to lower the bit in to the piece versus lifting the piece on to the bit thereby reducing the amount of material the vise can hold on to allowing to cant to one side which could cause the elongated holes at the bottom of the blanks.

Keeping the piece down where the jaws provide equal clamping pressure along the whole piece is key to this vise and keeping things from moving.


Lowering the bit into the piece has proved the best method for us to keep the holes round at both ends.

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Last edited by Mr Mac; 12-20-2010 at 02:25 AM.
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post #4 of 5 Old 12-22-2010, 07:33 PM Thread Starter
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Thanks for your responses.

Duncan, I've tried various amounts of pressure with no noticable change in results.

Mac, It's a 147 pound floor model, so I can't throw it very far. About 3 1/2" actual throw, plenty for any pen blanks I've used to date.

The good news is the source of the problem has been identified, but the problem isn't solved, yet.

I called an emergency meeting of the NCWTG and one of my friends played with all the parts. As he was drilling his 4th blank with the same resuilts I was obtaining, I could see, from 6 feet away, the jaws rocking almost imperceptably back and forth along the axis of the clamp's drive screw. By holding the the screw with a couple fingers or by gripping the jaws with a free hand the wobble is reduced ( but not eliminated ).

This clamp is better than trying to freehand it, but it leaves a lot to be desired, especially at the price Rockler charges for it. It's a pretty tool, but it it's a long way from being an effective tool on its own.

Again, thanks for the help,
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post #5 of 5 Old 12-22-2010, 11:03 PM
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Well that's not good ... makes me glad I built my own jig instead of buying a vise; mine doesn't center automatically, but it holds the blank in position and lets me slide it up the drill bit for a second or third press. (My bench-top drill press has only a 2" throw.)

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