Tail stock runout

[gerti]

I was just about to write about a problem I seemed to have with all my pen turning mandrels, but while describing it it occurred to me that the most logical explanation was that the problem was not with the mandrels but rather the tail stock. A quick check confirmed it: visible runout of the life center (cup and point).

My guess is that is not fixable, and I am looking at a new life center? Or are they adjustable?

Gerd

[Tom Hintz]

Gerd,
there is no adjustment in a live center itself. If it is bent or otherwise damaged, replacement is the only option.
However, on many lathes you can orient the tailstock (and headstock for that matter) slightly when clmaping it down by simply pushing or pulling on it horizontally when clamping. That tiny bit of change might be enough to get your centers matching perfectly.
I would put the drive center in the headstock and bring the tailstock up close, the points almost touching and see if they align or if you can correct the alignment by "setting" either (or both) when clamping in position. If so, you just have to remember to do that each time. My previous lathe needed just a little push on the tailstock when clamping to get it to run in perfect alignment with the headstock. Once I figured that out, most of my problems (and lots of vibrations) went away.

[kwgeorge]

I have the same problem Gerd with both the Grizzly and the Jet mini. In both cases I have found that if I twist the tailstock counter clockwise when I tighten it the problem is solved. Depending on the lathe you own you can adjust the headstock also. The best alignment procedure is to place a sharp spur drive in the headstock and a sharp pointed live center in the tailstock and bring them very close together. At that time you will want to compensate for any looseness in your tailstock either in the quill or where it meets the lathe bed ways. I do this by tightening the quill and twisting the tailstock counterclockwise and tightening. If you have one of the Jet 12” clones with a rotatable headstock you would just loosen it a bit and adjust to where the points of the spur and the center are aligned and then tighten it. If you have a Jet mini you can loosen the 4 Allen screws that attach the headstock to the lathe bed and adjust it slightly then tighten it back up.

[Tom Miller]

If your tail stock is the same as your headstock (i.e. MT#2, etc.) you could put your center in the headstock and see if it has the same runout. If so, you need a new one. If not, you may be able to fix the problem as the others suggest.

You could get a back-to-back MT made for aligning moveable headstock lathes, and use it to check and perhaps re-align your tailstock.

Regards,
Tom

[gerti]

The life center itself is bent. When I take the point out, set the cup on a flat surface and spin the taper by hand I can see it move off center... Looks like I'll be buying a new life center.

There are many great looking ones out there, all costing about a third of what my entire lathe cost!

Anybody got any experience with the Woodcraft 'Value-Priced Live Tail Centers'?

http://www.woodcraft.com/family.aspx?familyid=4436

Gerd

[Tom Miller]

Sorry, no experience with that one, but it sure looks like a good deal. If you go get it in person (Bloomington Woodcraft?) don't hesitate to chuck it up in one of their floor models and at least look for visible runout.

That less pointy point is just the ticket for most pen mandrels, BTW, rather than that pointier point (like the one I got with my Jet mini).

Regards,
Tom

[kwgeorge]

When I first started making pens I found that the tip of my live center would go blunt very quickly and become out of round. Closer examination showed 2 problems with this tip. First off it is very soft steel and deforms easily. Second its degree of angle is much greater than the end of the mandrel so only the very tip made contact.

A little researched showed that most mandrels are set up for a live center tip of 60 degrees. I purchased the following live center from HF and have been using it ever since. It has a hardened 60 degree tip.

http://www.harborfreight.com/cpi/cta...emnumber=38573

[gerti]

Figuring I do not have much to loose, I subjected the center to a few well placed precision-whacks with a persuader. Seems to have helped, runout is greatly reduced. Time will tell, though I will probably replace it rather sooner than later.

Tom, yes, I visit the Bloomington (actually was just there last Saturday). Good tip on checking it for runout on site.

Tom and Ken, good tip on the point. I'll be having a closer look.

Ken, thanks for the HF suggestion. Didn't even occur to me to look there, even though (or maybe because?) that's where the lathe came from...

Thanks all for your suggestions!

Gerd