Tennis Ball as Jam Chuck?

[Randy Heinemann]

I recently saw a picture of a "goblet" being turned using a tennis ball on the tailstock end for support; sort of like a jam chuck I guess. It seemed to me that, while the shape of the tennis ball might fit some pieces, a tennis ball might not be rigid enough and may vibrate loose. Given that all you see on the internet isn't right or even sensible, I thought I'd ask here and see what experience and thoughts others who would know had. There aren't many pieces I do that it would work for but it might come up.

 

[Kirk Amidon]

I've used a tennis ball and a whiffle ball for that purpose. Now I have a few cones I've turned for this purpose, which are better as they can be taped to the goblet and used to pull slightly away from head stock which helps with turning long thin stems. This is done with workpiece in a chuck at head stock.

 

[hockenbery]

goblet" being turned using a tennis ball on the tailstock end for support; sort of like a jam chuck I gues

tailstock support for a goblet is a different concept than jamb/pressure chucking a bowl

The purpose is to keep the goblet from whipping around on the thin stem.
I’ve seen Stewart Batty use a loosely wadded paper towel in the cup.
balls matched to cup size work well
The idea is to have something in the cup that protects the cup and will run true with no pressure

Sometimes the cup and ball will be taped to the tail center and the hand wheel opened to pull the stem straight.

I have several rubber chuckie screw on centers that work well for this

 

[Steve Saah]

Works extremely well for a wide variety of projects in the way @hockenbery mentions.

 

[Randy Heinemann]

Thanks for the input.

 

[john lucas]

I think a tennis ball is too big for my goblets. But then again goblet whip isnt much of a problem.

 

[Al Chavez]

Here are some jamb chucks I made on a live center. I had forgotten about them.
They worked well enough and may be just the tool for certain pieces. I have some Rubber Chuckies I tend to use most of the time now and a few wood turned cones (with the end threaded for a live center.
The white one is a rubber tip for a chair leg.
The other is a plunger.

 

[Barry Richardson]

Here are some jamb chucks I made on a live center. I had forgotten about them.
They worked well enough and may be just the tool for certain pieces. I have some Rubber Chuckies I tend to use most of the time now and a few wood turned cones (with the end threaded for a live center.

The plunger is brilliant, gotta have one now...

 

[Al Chavez]

Be sure to buy a new one.

 

[Don Wattenhofer]

I can honestly say that I have turned green wood natural (bark) edge thin walled goblets and never needed to support the cup with anything other then a a stepped approach to removing the outside wood. The black cherry goblets below were turned from a small tree with the pith included and the bark edge representing the outside of the tree. The walls are close to 1/32" thick and note the bark shrinks less than the wood result being the scalloped edge.
I have prepared a PDF document to try to explain the method.

 

[Ric Williams]

I can honestly say that I have turned green wood natural (bark) edge thin walled goblets and never needed to support the cup with anything other then a a stepped approach to removing the outside wood. The black cherry goblets below were turned from a small tree with the pith included and the bark edge representing the outside of the tree. The walls are close to 1/32" thick and note the bark shrinks less than the wood result being the scalloped edge.
View attachment 46683I have prepared a PDF document to try to explain the method.

Thanks for posting the pdf file!

 

[hockenbery]

When you need tailstock support for a goblet is dependent on the
The length and thickness of the stem and the cups weight and balance

Probably no magic numbers here but a 3-4” stem I probably don’t use a support
A 6” stem 1/8” thick I will need tailstock support

I use tailstock support for this unsanded oak goblet turned green.
Mi wife did not use tailstock support for this stemmed Holley vase

 

[Mark Jundanian]

Very clever.

 

[Don Wattenhofer]

A 6” stem 1/8” thick I will need tailstock support

it doesn't matter how long the stem is as long as you use the stepped approach and of coarse when you get to the point where you are turning the stem you will need to slow the lathe to prevent whip. The thinner the walls the less weight = less whip also those long skinny stems don't add to the design IMO. The best wow factor I think is the thin translucent and distorted walls.

 

[Dean Center]

It still wouldn't be the right size for John Lucas' goblet, but you can get dog balls that are tennis ball style, both smaller and larger than regular tennis balls, and they work fine, too. Getting the goblet and ball lined up so that the goblet is inline with the centerline axis is one problem with the tennis ball method. Something like a rubber chucky would be more reliably on center.

 

[robo hippy]

Al, you are a genius! Now I am thinking of the variations of plungers.......

robo hippy

 

[Tom Gall]

Those rigid styrofoam spheres sold in craft stores for decorating and ornaments can also be used. They come in several different sizes. Very light - and can be turned for any custom size if necessary. A reversed cone on your live center (i.e. Oneway and clones) work best but any center will work.

 

[hockenbery]

doesn't matter how long the stem is as long as you use the stepped approach and of coarse when you get to the point where you are turning the stem you will need to slow the lathe to prevent whip.

I’m impressed that you can turn a 12” or 18” tall stem 1/8” thick or less without tailstock support or lathe steady.

I do use a stepped approach. Cutting the stem is not the reason for the tailstock support. I have to use tailstock support to keep the cup from whipping about at any reasonable cutting speed.

Thin tall stems have more flex than I can control without tailstock support.
Also the stem in green wood will often begin bending some as the wood dries so I would have whip at any speed.

 

[Don Wattenhofer]

I’m impressed that you can turn a 12” or 18” tall stem 1/8” thick or less without tailstock support or lathe steady.

I do use a stepped approach. Cutting the stem is not the reason for the tailstock support. I have to use tailstock support to keep the cup from whipping about at any reasonable cutting speed.

Thin tall stems have more flex than I can control without tailstock support.
Also the stem in green wood will often begin bending some as the wood dries so I would have whip at any speed.

I have to admit that I never do those long thin stems in my opinion they don't do anything for the form they just make it look all out of proportion.
The problem with the stem bending is due mostly to the reaction wood near the pith that always wants to go back to it's original shape that it had before it was locked into the center of the tree. The pith itself can be a problem if it is in the exact center of turning, but if you center the turning on the outside of the tree the pith is rarely in the center of the turning and that makes it necessary to have the cup wall thin enough that the pith will dimple instead of cracking. The stepped approach can be effectively used on the stem also because even on a short stem they will bend as soon as the reaction wood is released.
We could go on and on about the tips and tricks involved in this type of turning but the best way I can say is practise / analyze what went wrong - repeat. The material to practise with is the small trees and limbs that most turners don't recognize as being good for turning.