A couple comments on using liquid nitrogen for freezing parts for
machining.  Carrying liquid nitrogen in a Thermos bottle works fine,
but

   ** Do not put the stopper in tightly ! **

Extreme pressure can build up in a short time and cause the Thermos to
explode.  Neither the glass nor stainless steel containers can contain
that pressure.  Place the stopper loosely on top, or just cover with a
Thermos "cup", but assure that either is loose.

Transporting a Thermos, with a loose stopper, in a car is asking for
spillage.  Don't allow liquid nitrogen to spill on you (especially on
your clothes or gloves).  It soaks through and freezes you in a flash.

It's very painful and takes a long time to heal.  Take it from me --
I learned the hard way!

Larry Martin