Mandrel help

[turn360]

Hi Everyone, The shaft on my pen mandrel was slightly off at the tailstock end. So I replaced the shaft and added a mandrel saver. I am still experiencing some minor vibration but I want to eliminate it. When I line up the points of my drive center and live center they are dead on. How do I tackle this issue? Thanks for your help.

 

[Charlie_W]

Hi Everyone, The shaft on my pen mandrel was slightly off at the tailstock end. So I replaced the shaft and added a mandrel saver. I am still experiencing some minor vibration but I want to eliminate it. When I line up the points of my drive center and live center they are dead on. How do I tackle this issue? Thanks for your help.

I have two thoughts on this. First, have you rotated the spindle without the mandrel saver to see if the mandrel is turning true?
Next, there could be some play between the mandrel saver bore and the mandrel itself causing vibration towards the tailstock.
I am assuming this is a fixed shaft mandrel which screws into the Morse taper. An adjustable mandrel may work better for you.

 

[magpens]

Please give more explanation ... what do you mean by "slightly off" in this statement:

"was slightly off at the tailstock end"

Do you mean that the end of the mandrel is not centered on the live center point ?

You have actually made two changes at once:
1) replaced the mandrel
2) added a mandrel saver

Better troubleshooting practice is to change one thing at a time and note the improvement or lack thereof.

 

[philipff]

Are you mounting the mandrel in the #2MT headstock directly or in a chuck? A chuck is a NO NO. You will induce vibration by using a chuck.

 

[Paul in OKC]

Make sure your head stock taper is clean. Also are you using a 60* live center? If it is the stock wood turning center, those are not 60* and the point hits the bottom of the 'dimple' in the end of the mandrel. You can get away with that by filing off the tip until it hits the tapered part. It won't be exact full contact, but it will run true. I did that for years before getting a 60* center.

 

[Aces-High]

I sometimes have this as well. Once the mandrel is mounted, I alway check if it is turning true before I bring up the tail stock. If it is not, often I can jut give the mandrel a "bump" on the side that is out of alignment and it helps.

 

[leehljp]

Agree fully with "Paul in OKC's" post.

 

[MiteyF]

I stopped using my tapered mandrel collet altogether, in favor of the PSI collet chuck. My mandrel runs far more true now. The mandrel saver is also wonderful.

 

[turn360]

Thanks Charlie I will check the mandrel saver for play.

 

[turn360]

Thanks Mal, Yes the shaft is slightly off at the tailstock end. The mandrel center brings it back in line. So that is the end where I notice the vibration. Near the headstock I get no vibration. I will fiddle with the tailstock end get it spinning true. I am using an adjustable MT2 pen mandrel when I change the length of the shaft would introduce vibration?
Jerry

 

[magpens]

There are so many factors that can play a role here that a "one size fits all" answer is impossible.

Everybody's setup and equipment origin/history is a little different.

You can mount the headstock end of the mandrel in a MT taper, in a chuck's jaws, in a collet chuck, etc. . All will work and work well depending on "other things" which only the operator can certify as OK.

At the tailstock end, the quality and fit of your live center, and the fit of your MT taper to the tailstock body (including the possibility of foreign matter) are factors. Also the shape of the point of your live center and the shape of the dimple in end of mandrel, as others have said. . Not to mention the bearings in your live center ... they have a limited life and are often a reason to discard a live center or give it to a starting-out pen maker !! :biggrin:

Even with a mandrel saver you have worries like foreign matter inside the tailstock body, clearance fit of the mandrel to the mandrel saver, bearings in the mandrel saver, inaccuracies on the tapered arbor of the mandrel saver, etc. ... even the tightness of the locking lever on your tailstock can play a role.

 

[turn360]

Thanks for all the good ideas. Appears I have some work to do to fix this.
Jerry