Pen Question #5--Ovalling the blanks

[Dean Thomas]

Hey gang. I have two questions offered in two threads here. This first one is a lift of my response to Dave Stoler's issues about alignment. I've become increasingly aware of just the thinnest of edges at the hardware connection on a few of my pens, and I want/need to fix it. Here's the situation.

Had a blowout on a bowl. The blowout apparently caused the Mayo 1236 head to move a smidge. Made my mandrel about 1/8" out at the end of its world which was more than enough to bow the mandrel and make oval joints instead of round. Too thin on one edge and too fat on the other. Not a nice feeling. Re-aligned and reduce the problem by 90%, but there is still an ovaling problem. Checked and at least one of my mandrels does not fit my Morse taper hole well at all. Sucks in fact. Now I have other issues to conquer in my quest for pen barrels that perfectly match the hardware. And I'll probably end up with some new bushings, too, as I've discovered that some of them (even the new ones!) are simply not tolerable when it comes to round and equal on the mandrel!

Are there mandrels that are better than others? I think my questionable one is my newest one from Woodcraft. Chinese special, sigh. The area of the mandrel that I can touch when it's in the hole (call that the front or fat end) seems to fit just fine, but there are times when I can grab the mandrel and it seems to pivot on that front and it seems to rock in the socket. I'm going down now to see if I have the same issue with my other mandrels. I cleaned out the sockets really, really well, so it's not a dirt issue. If I can't get 'em to fit, they may be going back to Woodcraft.

So far, I've:

made certain that the alignment of the head is spot on
made certain that the spindle spins without run-out
cleaned the mandrel and the drive centers
cleaned the taper hole
rechecked alignment
checked bushings to make sure that they are round and that each has its hole in the middleStill not getting perfect fits to the pen kit hardware. Fits on one side with just enough lip that I can feel it on the opposite side. Am I expecting too much? I surely hope not! :confused:

I still need to check the hole itself for run-out, but I surely hope that's not the problem.

Thoughts, experiences, other ideas?

[Bernie Weishapl]

Dean I had trouble with a mandrel I bought at Woodcraft (cheap). So I bought the A and B mandrel from Berea Hardwoods. Haven't had a problem since. I to noticed bushings coming from Woodcraft were also not very well made. So all my bushings come from either Berea or Bear Tooth Woods. No more problems.

I am guessing the only thing left is your mandrel. If you have your headstock aligned and then put you mandrel in the headstock and bring up the tailstock it should be straight and if not I would get a new one.

[Alex Elias]

There are two thing you have not checked yet. First is the the live center has the same angle as the dimple on the mandrel. I think it should be 60 deg. The ones that come with the lathes are not the same and it is very important to have a maching fit. The other thing is that often enough one puts to much pressure on the tail stock and that will cause the mandrel to flex. The other thing you can try is to make the mandrel shorter and turn one half at the time. (shorter shaft less run out)
I switch a while ago to the beal chuck to drive the mandrel and I'm very happy.
Good luck and let us know.

[Dale Johnson]

you can eliminate the mandrel and turn weth a dead center for drive and a live cone center in the tail. put the points of the cones in the bushing holes and use the bushings like normal. this only lets you turn one half at a time, but no out of round. you can also go to a collet chuck and shorten the mandrel and only turn one half at a time. the shorter the mandrel, the less runout.
dale

[Paul Heely]

I also turn some of my better pens without a mandrel, using a dead center in the head stock and a 60 degree live center. I go one step further though. I make my own bushings out of delrin. I find I get a much better fit where the bushing goes into the tube.