Pen Mandrel Runout

[Jon McElwain]

I just received an adjustable pen mandrel a couple of days ago. I put it on the lathe without a blank to see how it worked and noticed a little wobble. I thought perhaps I had the tail stock adjusted too tightly, but it was barely touching. I backed the tail stock off; still wobbled. Tightened it up a little, still wobbled. I re-set the mandrel in the lathe and cleaned all the parts to ensure that there was no dust in any of the fittings. Still wobbled. Next I pulled out a dial indicator on a magnetic base and measured 0.006" of runout. It was nearly perfect at the headstock end, and down to 0.002" at the far end. It appears that the worst runout is near the middle of the rod.

The questions are; will this effect the final alignment of my tuned pen blanks to the metal pen fittings (I assume yes), and have any of you had a similar problem? Am I better off sending it back for a replacement?

Thanks,

Jon

[Kyle Iwamoto]

Can you pull the rod out of the mandrel? If it's like mine, the rod is removable. Take out the rod and roll it on a tablesaw or something known flat. You'll be able to tell if the rod is bent. It takes only a little to get it bent. You can just as easily straighten it.

[Andrew Kertesz]

Yes it will affect your fit and finish, it would be like doing an off center turning. You can buy replacement rods for an adjustable mandrel. It doesn't take much to bend them that is why many people turn pens between centers and don't use a mandrel.

[Michelle Rich]

I concur with Andrew. If you are turning anything other than 7mm pens, skip the mandrel all together. Turn between centers, one barrel at a time. Your OOR will be a thing of the past

[Bernie Weishapl]

My mandrel had a slight runout and did like Kyle suggested. I pulled it out and rolled it on my tablesaw table. It didn't take much to straighten it. Had less than .001" from one end to the other.

[Jon McElwain]

Thanks guys. I'll try the tablesaw method. Hopefully I can bend it back to true.

[Mike Ragsdale]

i had a similar problem and bought a new one only to find it did not fix the wobble. Went back to the store and tried several in their lathes and found none without a wobble. Then went and bought a long 1/4 drill bit and cut the drill off and made a mandrel out of it. There was still wobble at the end when unsupported. While bad and bent mandrels do exist even new ones what I found is the way it mounts in the collet will make a big difference. I lubed the collet with anti seize and worked to center it as much as possible. It never was perfect unsupported but I use a PSI mandrel saver in the tail stock and with it there is no notable movement and blanks match hardware.

Thanks
Mike