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Old 04-26-2014, 07:43 PM   #1 (permalink)
 
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Default Off Center Holes in Pen Blanks?

I have to admit I'm a 'Newbie' to Pen Turning but have turned bowls, boxes, bird houses, kitchen tools, etc. for a couple of years and never had an issue like this... I recently started turning pens and purchased all new pen turning tools (i.e.; PSI Pen Blank Drilling Vise, Pen Assembly Press, required brad point drill bits, blank squaring tools, etc.) and find that 3 out of 5 pen blanks that I drill are centered on the top of each blank but off center at the bottom of the blank so much that I feel the blank is a complete loss! I've checked the drill press to be sure it is square and level and that the drill press is running at the correct speed, stop often and clean out the drilled hole and let the wood cool, etc. yet still find that the majority of the blanks I drill are off center at the bottom of the blank... What gives? The wood I've used is Cocabola, Purple Wood, and Walnut blanks from PSI and other suppliers... Any/all assistance/advice will be greatly appreciated! Safe turning to all!
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Old 04-26-2014, 07:57 PM   #2 (permalink)
 
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I don't think you really have a problem.

The hole doesn't have to be exactly centered in the blank. Remember that a finished pen consists of a brass tube with a relatively thin layer of turned wood (or plastic) on the outside. The axis of the finished pen is determined by the axis of your mandrel, and the outside of the finished pen will be whatever you turn it to be around that axis. The fact that when you start turning the blank isn't exactly centered on the mandrel is unimportant.

What does matter is that the hole that you drill remains straight and comes out the end of the blank (and not out a side), that there is enough wood between the exit hole and the side of the blank to form the desired thickness of the pen body around the hole and tube, and that the ends of the blank are milled to be exactly perpendicular to the tube (and hole).

Most of the material that starts out as a pen blank is removed in the process of making a pen - you start by drilling out a fairly large hole that you then glue a tube in, and then you turn away all but about 1/16" of wood on the outside of the tube.
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Old 04-26-2014, 08:07 PM   #3 (permalink)
 
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If it's that the hole is OOR, try not using a brad point bit. They tend to wander a bit when they first touch the wood. Also, if you want a perfectly centered hole each time, drill on the lathe. I personally enjoy drilling on the lathe because it's so much faster for me.
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Old 04-26-2014, 08:09 PM   #4 (permalink)
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Your problem comes up once in a while, so I have made a couple drawings.

The problem is, nearly always, that your drill press table is NOT perpendicular to your drill bit. In other words, the table is crooked. See drawing one.



To test, make a half a Y as shown, from an old wire coat hanger. Insert the wire into your drill head and turn it BY HAND!! Set it so the wire just touches one point on your table. As you turn the drill head, the wire should touch all the table exactly the same. If it does, your table is FLAT and perpendicular to the drill head. Most likely, your holes will now be straight.



Hope this clears it up!!

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Old 04-26-2014, 09:22 PM   #5 (permalink)
 
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I read the OP question and I was going to reply and I what thinking that I needed to first go into my "Paint" program and draw up something, it wasn't going to the the bent wire trick, that I never heard of it before and I reckon is one of the simplest ways to test the drilling system, that I've heard of so, who ever come up with that idea, he/she is a smart "creature"...!

So, reading through and seeing your post and your simple and clear drawings/diagrams, I was happy to give up of any drawings of other ways to do it, and applaud/support, what you gave us, its good enough for me, and should be easy enough to follow, by everyone else...!

Thanks for that...!

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Old 04-26-2014, 09:43 PM   #6 (permalink)
 
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End grain drilling in wood isn't easy, and oily wood makes it worse. Bring the drill out of the wood, A LOT! If the flutes fill up, they will wander more.
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Old 04-27-2014, 01:08 PM   #7 (permalink)
 
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Thanks everyone! Some great ideas that I haven't tried and I will try the 'ole wire' trick to see what happens. Maybe I can salvage a couple of the blanks as they do still have more than 1/16th of an inch of wood left on one end. Thankfully, none have ever come out the side of a blank, but sometimes fairly close. I just hate to loose nice blanks!
Again, Thanks and safe turning to all!
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Old 04-28-2014, 09:51 PM   #8 (permalink)
 
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Quote:
Originally Posted by Cmiles1985 View Post
If it's that the hole is OOR, try not using a brad point bit. They tend to wander a bit when they first touch the wood. Also, if you want a perfectly centered hole each time, drill on the lathe. I personally enjoy drilling on the lathe because it's so much faster for me.
I used to have the OP's problem until I read posts like this one. I bought the PSI blank chuck and mandrel saver. I had a pen drill vise, but never could get the holes to come out straight. I tried using a square to make sure the dp table was perpendicular to the bit, but never could get it quite right. Even drilling blanks on the lathe, sometimes the hole is a little off. I think that there's some play in the pen blank chuck jaws and/or the keyless chuck may be slightly off. I went back to my old JT33 today with better results. I find that I really have to back the bit out often to avoid burning. I'm drilling at around 300 rpms. Not sure it that's the right speed to use either. If the hole is a little off, you'll still have plenty of stock to use but it will take a little longer to bring it into round.
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Old 04-28-2014, 10:29 PM   #9 (permalink)
 
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I have a small level....I put it on the table and when it says the table is level it's square to the bit. I also have drilled holes on the drill press come out off center from where they went in....and the next blank and the blank before were perfect. So I think Ed's solution is right on most of the time it isn't always the answer.
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Old 04-29-2014, 07:48 AM   #10 (permalink)
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When speaking about procedures in penmaking, I have often said, "This is the way I do it, there are many other ways that may work just as well--if you are using a way that works for you---keep doing it!!"

What I don't say is equally true---there are MANY ways to do it wrong, so one solution will not fit EVERY problem.

BTW Smitty, your level will work fine, as long as your floor is level. If the drill press is standing on a crooked floor, making the table completely horizontal will not result in a straight hole. The coat hanger trick will make the table perpendicular to the drill head, which will result in a straight hole. (unless the bit itself is bent, but that would mean only one size hole would be crooked and more likely it would be oversize, as well.)

FWIW,
Ed
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