Help Making Pens!

[=Adam=]

Hi guys!

I am having some trouble from my pen mandrel when I am turning my pens!

I mount the blanks on the lathe, tighten the screw to hold them in place and then bring the tail stock up. I make sure not to tighten the tail stock too much, just enough so that there is light pressure and the centre starts spinning.

What I then find is that when I am getting close to my finished dimensions there seems to be some chatter coming from the madrel, I am positive that it is not from the tool as I have taken a light cut with my skew (just about grazing the surface) and placed a good bit of pressure onto the tool and it still happens!

The chatter is most pronounced near the headstock and is totally fine at the tail stock, so I am not too sure on the cause of this, could it be that the mandrel has bent and is causing the chatter?

I forgot to mention that the chatter is leading to me making more oval pens as opposed to cylindrical, only slightly but I like things to be as they should!

Any help would be great guys!

Thanks

 

[CHJ]

Are your pen sleeves a close fit on the mandrel or correctly matched to the adaptor bushes?

 

[=Adam=]

I believe they are, they slide on the Mandrel nicely, not forced on and I tighten the locking nut nicely so that they sit tightly on the bushes.

Is it possible that I am tightening the lock nut too much?

 

[CHJ]

....Is it possible that I am tightening the lock nut too much?

Difficult to do with the fingers.
Are your blanks trimmed flush with the tube ends?

Do you have a picture of your mandrel setup on the lathe and the fittings you use?

 

[Spindle]

Hi

It sounds like the tool is bouncing, on a larger diameter piece you would see 'barley twists'. Try cutting in the other direction, supporting the work fom behind with your fingertips, varying the lathe speed.

Regards Mick

 

[nev]

a couple of things I would check if it were me going wobbly.
1. is the headstock lined up correctly with the tailstock? (likely)
2. if the mandrel and rod come apart, separate and roll the rod over a piece of glass or known flat surface to check its not bent.(unlikely unless you're a touch over zealous on the tightening)
3. is one or more of the bushes you are using 'off centre'? I did have one of one set once with the hole not quite in the middle. The tubes on the mandrel shouldnt matter because the tube sits on the bushes.
4. Could possibly be the grain of the timber going the 'wrong' way, do you cut in both directions? and do you get the same chatter up and down?
5. Is the mandrel MT fitted into the headstock completely? mine does not fit correctly if i have the thread saver fitted resulting in the issue you are having.

 

[Robbo3]

Nev beat me to it

Once chatter or rippling starts it is difficult to overcome especially on small work such as pens. Less pressure from the tool & a finger (or fingers) behind the work to steady it - if you are adept enough.

You may have to rig up some form of steady to rescue the pens with problems.
Easiest is probably an upright with a 'V' notch cut so that it runs on the spacer.

String Steady Rest
- http://www.hiltonhandcraft.com/Articles ... Steady.asp

If you can find a copy, the December 2001 Woodturning magazine had a good article by Gabor Lacko on lathe steadies.

Robbo

 

[CHJ]

If you have blanks that are prone to the tool bounce or go out of true for any reason try using a wood block backed abrasive sheet to even things out.

 

[=Adam=]

Thanks guys!

Ghj, what is that curved spacer for on the left of the mandrel? I have some of them but not sure what they are for!

I like the idea of making a steady, I will give it a go if I can't sort it out another way!

My blanks are squared off to the barrel using the trimmer so that isn't an issue, along with the fact that I cut both ways (left and right) and still experience chatter in the same place so the grain direction is ruled out.

I will sand with a square block from now on just to rule out human error.

 

[CHJ]

.....Ghj, what is that curved spacer for on the left of the mandrel? I have some of them but not sure what they are for! ......

It's not a spacer in this instance Adam, it's just the form of my home made mandrel which I clamp in the chuck.

 

[=Adam=]

Thanks for all of the replies guys!

I believe I have narrowed the issue down to 2 things:

1) my headstock was ever so slightly out of line with the tail stock.
2) the bushes appear to be off centre, therefore leading to the chatter.

Hopefully these issues will be sorted soon!

 

[DUNK_WALES]

I have experienced a similer problem and the cause was my headstock was not properly alligned with the tail stock it only needs to be slightly out to cause problems. good luck