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Markus666 03-10-2017 02:48 PM

Drilling pen blanks
 
Hi all. I'm hoping you can help me with a blank drilling problem I keep having.

I drill both wood and acrylic blanks using the bit sizes specified in the assembly instructions (from PSI). I drill with a Jacobs chuck on the lathe at around 500rpm and I back out the bit several times to remove scrap from the hole and the bit. When I dry fit the tubes, the drilled blank holes are always too big, forcing me to wrap the tubes in masking tape prior (to snug the fit) to gluing them in. Does this happen to other folks too or am I doing something wrong? Is masking tape a reasonable solution or should I be doing something else?

Thanks so much for helping out a fellow turner.
Mark

skiprat 03-10-2017 02:56 PM

Welcome:wink:

Sounds like you have a tailstock alignment issue to me.

mecompco 03-10-2017 03:01 PM

Yup, somethings not right. I've only had that happen with one 12.5mm bit--replaced it and all is good. Now how oversize is the hole? I'm not thinking I'd trust the tape trick to last. I always use epoxy and you can goop enough in to fill holes that are slightly over-sized, as sometimes happens and all is good.

Regards,
Michael

randyrls 03-10-2017 04:54 PM

Quote:

Originally Posted by Markus666 (Post 1910901)
I drill both wood and acrylic blanks using the bit sizes specified in the assembly instructions (from PSI).

Mark; I often find the sizes of drill bits that give me the best fit are NOT the ones on the instructions. The drill bits specified are the closest most common available size.

I have a 115 piece drill bit set and a 25 piece metric set. When starting on a new style/model, I drill a hole that is smaller than I think is correct. If the tube doesn't fit, step up to the next size larger until the tube just fits. Then write down that drill bit size on the instructions for the pen. There are several drill bit size charts in the Library.

Oh; added later, drill no more than 1/2" at a time.

Hope this helps...

MillerTurnings 03-10-2017 05:08 PM

I normally drill .010" over the measured tube size, this leaves room for paint and epoxy.

ALA 03-10-2017 05:55 PM

1 Attachment(s)
A drill bit guide is very useful in this instance. Insert the tube into the guide for a reference. Of course, leave a little room for glue when selecting the bit. :smile:

mark james 03-10-2017 06:29 PM

G'Day Mark,

All the suggestions above on drill sizes and drilling technique are all excellent. I can only add to combine those thoughts with the first suggestion posted by Skip... Check your Tailstock. Make sure your headstock and tailstock are in alignment, and that the tailstock is able to be tightened accurately. After that - yup, check your drill technique and the drill dimensions.

Dale Allen 03-10-2017 07:58 PM

If the bit shakes or moves from center while drilling then something is not aligned right as stated above. You should feel almost no vibration or movement of the drill bit and drill chuck when drilling.

Bob Kardell 03-10-2017 10:30 PM

One thing to think about is when you back the bit out don't loosen the tailstock. I made the mistake early on of loosening the tailstock each time I backed out the bit and each time you do that there is a chance that it will not tighten in the exact location and this will cause the hole to widen.

When the tailstock has been extended as far as it can go and you have not gone completely through the blank - back out the bit without loosening the tailstock, stop the lathe, loosen the tailstock, move the bit forward into the blank, tighten the tail stock again, then start the lathe and start advancing the bit again. The longest blanks should only need to have the tailstock reset once ....

Hope that helps.


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jttheclockman 03-10-2017 10:33 PM

All good suggestions above. I will add also when you have the drill chuck in the tailstock, just snug up on the holding lever. And as you advance the drill bit hold the chuck with your left hand to steady it as it enters.


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