Mandrel - what am I doing wrong?

[bwebb]

I just started working on my 4th pen, and my mandrel seems bent. The blank closest to the tailstock just doesn't turn as smooth as the blank nearest the headstock.
I have a mandrel from Woodcraft. I pulled my tailstock live center just snug to the mandrel, and tightened the brass knob just tight enough to keep the blank from slipping while turning. I can't seem to get the bend out of the mandrel. I need help straightening things out!

 

[redfishsc]

I have what seems to be that exact problem with a woodcraft mandrel. I'm interested in hearing what's up. I, like you, do NOT tighten the brass knob any more than necessary.


I suspect part of the problem was the live center I used. It was a Woodcraft cheapie. My next one won't be a crap one.

 

[dubdrvrkev]

Okay, common issue. But there are 100 acceptable answers.
To get the bend out, what I do is bring the tailstock up to about 1/8" away from the mandrel. Then, by hand, turn the spindle so you get an idea how much its bent and where it tracks. Find the point where the mandrel end is at its highest point, then hold the hand wheel steady and give the mandrel a little push down. Repeat until the mandrel runs as straight as possible.
It sounds like you took the right steps to keeping it straight but remember, if you get a catch the nut likes to tighten up a little and if your tools are dull you could be pushing a little hard against the blanks. I've also noticed that the compression fitting that comes with the WC mandrels can put a bend in them. I use it for a spacer, but just let it slide all the way up and just barely finger tighten it.

Good luck.

 

[bwebb]

I'll try loosening up the compression nut. I have mine pretty snug about 1/2" from the tapered end.

 

[terrymiller]

So far I have bought most of my stuff from Woodcraft including the mandrels. I to have had that problem mine was not from tightening the blank on the mandrel to tight it was from tightening the tailstock to much on the mandrel. From what I have been told you want it firm not overly tight. After doing this I have not had a problem with the mandrel bending.

 

[ed4copies]

Woodcraft sells replacement mandrel shafts. In the early stages of turning, if you are getting "catches" you could bend the shaft. Rather than play around with bending it back, buy a few of the shafts ($5 ea, I think-it's been a while). Or, if the pens are just to give you practice, bend it back to close.

Set up the mandrel with no pen parts on it, as you would to turn. Turn on the lathe and put your finger on TOP of the mandrel at its midpoint. Turn off the lathe, as it slows determine which is the high side of the shaft. When the spinning stops, push the high side down and repeat. When you can't feel a difference, you're close.

[]

 

[ncboyntx]

I also have this problem. One of my Woodcraft mandrels will not seat properly in the headstock, it has a slight play when moved up and down. I will take it back. Can someone suggest a better mandrel perhaps? I don't mind paying extra for a mandrel if it will eliminate the frustration.

 

[knottyharry]

Hi Brian,
Two things.
Is this a mandrel that slides in a collet? If so don't over tighten it. Snug should be good.
Also, too much pressure from the tailstock spindle will cause the problem you are having.
Run the spindle up to where the live center starts to spin, and just a touch of pressure. That is all you need you aren't supporting any weight here so really watch the pressure.
Harry

 

[Mikey]

LOL, I have the same problme wit my WC mandrel, except new shafts don't help. Could be a cheap live center, or perhaps there is a problem where the shaft tightens into the headstock end. My problem is consistent from Delta Midi, to Rikon, to the Jet and Delta they have at WC in their classroom.[]

I haven't had the time to go buy another new mandrel yet.

 

[William Young]

As soon as I saw this topic I was going to answer because the same thing happened to me yesterday when I was starting to turn a pen. This same mandrel has turned 150 pens now and this was the first time I saw a bend in it.
So I did exactly as Kevin so nicely explained and all is well now. I went ahead and turned this bocote pen with pink ivory center band on my straight mandrel.
W.Y.