On 12/10/2015 07:35 AM, Electric Comet wrote:
On Wed, 9 Dec 2015 16:00:14 -0700
graham wrote:

I generally use the stub of whatever is left over after parting off
the turning.

not sure if we are talking about the same thing

the jam chuck example i saw was a small toy top jammed into a hole
in a chucked piece

are you talking about jamming between head and tail

Often, when people turn things like boxes, the stub left over after
parting off makes a good jam fit chuck. In that case you would cut the
tenon on the stub so that the piece fits over it, rather than into a hole.

Other times, it makes sense to turn a recess in the jam fit chuck and
put the piece into the hole as you describe. It just sort of varies
with the application. The idea is essentially a friction fit, either
holding on the inside or the outside of the piece depending on what
would give the best grip...

....Kevin
--
Kevin Miller
Juneau, Alaska
http://www.alaska.net/~atftb
"In the history of the world, no one has ever washed a rented car."
- Lawrence Summers