Out of round barrels

[JohnU]

Ive run into this in the past where my tips didnt set center in the blank after assembly because there was more wood on one side than the other due to my tail stock center was worn out from being pushed to hard into the mandrel and when I tried to grind it down to a point agian, it didnt grind down evenly so my point was not in the center which caused the mandrel to wobble up and down when it turned and not spin level. I would check the tail stock because like above, if it spins true, your brass tube will be in the center of your turned blank no matter how much glue or wood you have around it.

 

[Firefyter-emt]

Well Dan, your tailstock needs to come towards you a little bit. Can you adjust it, or unbolt the headstock and tweek it towards the back a little? The run out sounds fine for a wood lathe to me.

Oh, and wear your sunglasses when using that pen mil! Do you like the shine?

 

[Dan_F]

Lee---That's a big 10 4 on the shine! I made the first sleeve last night out of delrin, now that's some strange material to work with. Ribbons like acrylic blanks, but much tougher, making it harder to keep them out of the way. I used the mill on a barrel upon which I had just completed the finish, and it worked very well.

Update--It seems I had a residual bit of CA on the dead center from finishing another pen, which may have contributed to the problem, as well as the questionable barrel milling. With the new mill form Lee, I can rule out the latter. I will also see if I can find out how to tweak the last little micron or two of the alignment of the head and tail stock, without going out in the opposite direction. Then turn another Carbera, and see if the problem persists. Thanks for all who have contributed tot his thread, and dispelled the ill centered tube notion.

Dan

 

[Rifleman1776]

Originally posted by Paul in OKC

I get amazed every time the out of round blank thing comes up. You can't turn something out of round without an eccentric chuck. No matter how wobbly your set up, your blanks will be round! Out of concentricity, but ROUND. Now, my opinion on the matter is that something is out of 'true'. In my mind, no matter how oversized the hole is, when trimmed and turned, it will be round. Might be thicker on one side than the other,(the 'gap' will be full of glue on the thin side) but if everything else is TRUE, the diameter will still match the hardware, and it will be round. I have turned some loose tubed pens, and if the barrells are thick enough when finished (not slim line) Every thing is good. If I had time I would do some over kill on a couple of pieces and do a non-scientific professional machinist test just to prove it . So, my thoughts are that something is ****-eyed, or bent. Or you are using the wrong size shaft for the tube on your pen mill.

Paul, I know you are a machinist and can probably refute my statements with some very learned tech- talk. But, I'm here today to tell you my experience.
Simply, using a mandrel, YOU CAN TURN OUT OF ROUND. Before going to the 'no mandrel' method, I was constantly frustrated by the ends of my turned pens being OVOID in shape. They simply were not round. This was with my old Grizzly lathe. Using the same lathe and going with the 'no mandrel' method, ends were round. With mandrel, not round. Ovoid/oval. I can only guess it was caused by flex with the mandrel rather than a non-concentricity issue. That's an eyeball on the issue report. Cheers, Frank
EDIT: for the record, same experience with a variety of mandrels. Much less so and issue with an adjustable mandrel doing only one half of the pen at a time.