Doh! Doh! Doh!

[Jason Christenson]

I turned a pen last night (pencil actually) and I'm having the same problem I had when I first started, that is, my blanks come out just slightly out of round. Essentially, when it's flush with the bushing on one side, it is just barely proud on the other. My mandrel is straight, any other suggestions? I have a lot of Christmas presents to turn and I need them to be round!

Jason

[David Fried]

I've gotten the same effect when I over-tighten my tailstock. It flexed the mandrel so things came out a little off but when the mandrel was out of the machine it was straight. Applying less pressure cured it for me.

Just one possibility.

Dave Fried

[Chris Barton]

Are you certain your mandrel is strait? I have had considerable problems in the past with one particular brand of mandrels (Woodcraft Professional) and encountered that very problem. Try this, place your mandrel in the headstock and bring the tailstock and live center up to but not touching the end of the mandrel (say a mm away) then rotat the head stock by hand while watching the end of the mandrel by the tailstock. If it rotates in an arc then you mandrel is not strait and that will translate into the problem you describe.

[John Hart]

I get this behavior when my tailstock is not true to the mandreal then to the headstock. This can occur even if the mandrel is straight and is noticeable as you can see and feel some wobble or vibration in the bushings when they are spinning. Ideally, there should be zero deflection.

I don't know how you are meeting up to your mandrel with your tailstock, but that's the point where I would be suspicious.

[Randy Meijer]

Another thing that could be happening.....and I have never seen this mentioned on any pen-turning board, before......is a speck of debris in the dimple on the end of the mandrel. Be sure the mandrel dimple and the tapers on your HS and TS are clean!!


Russ Fairfield has a very good set of instructions for tuning up a mandrel so it runnung true. Try looking at this and see if it helps:

http://www.woodturner-russ.com/Pen12a.html (http://www.woodturner-russ.com/Pen12a.html)

[Jeremiah Jordan]

I know exactly what this is! I have been struggling with this problem for years. You might be drilling too fast or having the drill bit out of round. Have you noticed that when you glue your tubes in, there is a space on one side and not the other? I hope this is what it is. I can not telly you how many mandrels I have gone through not regocnizing that it was my drill bit that was the problem.

Hopefully this works for you!

Jeremiah

[Randy Meijer]

Even if there is some problem with the hole, once the tube is glued in, if the mandrel is straight, the surface of the wood will be turned parallel to and concentric with the long axis of the tube. Sorry, but I don't think a bad hole should cause an oval or off-centered barrel.

[Bill Pealer]

One other factor is that the the nut on the mandrel may be too tight. That will have the same effect as the tailstock being too tight.

[Jeremiah Jordan]

The problem i just had with a blank was that the hole drilled through, down at the bottom, was larger in diameter that in the top. This will just put the bottom side of the blank up over the bushing. I will have to post a picture this afternoon after i get back from college to show you guys.

Jeremiah