On Wed, 20 Jun 2018 20:14:28 +0100, David Billington
wrote:

How about the mandrel pin vice listed here
https://www.arrowsprings.com/html/holding_tools.html about 2/3 the way
down the page.

Too short for the job - will burn the fingers quickly. Probably won't
work after the first heat because the fingers are de-tempered.

Glass workers have had a couple thousand years to perfect their tools.
It is VERY difficult to improve on what is traditional. I know, I've
tried.

Graphite is the traditional mandrel material but it oxidizes quickly.
Tungsten was a great improvement but it must be coated with a release
substance because glass wets tungsten. The usual release material is
colloidal silica.
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address