David & Guys,
Holding the pan against the grinder is unsophisticated, here is the setup. The grinder is clamped in a post vise and a small wood block is clamped to the bench beside the vise. The wood block has a small wood stop block nailed to the top surface. Clamp the wood block in a position that brings the uncut pan under the cutter.
With the front end of the gunlock bearing against the wood block, just pull up by hand pressure (a third class lever here) while rotating the cutter. Notice that fine positioning is by some very precision wood shims (popsicle sticks!) You do not need to use a lot of force.
This photo shows the partially cut pan. I don't finish cut the pan until after the lock is installed on the gun. This allows for any small adjustment to align the pan with the existing flash hole.
This photo shows all the parts needed for the pan cutting job.
Here is the pan grinder in its storage box.
Thanks for the interest.
Jim