There’s been some discussion on the
Gun Building forum about grinding octagon flats on a round barrel. Here is a jig built in our shop for grinding flats using an angle grinder. It’s easy to build and easy to use. It’s a simple machine made of scrap lumber, angle iron and steel plate. The steel top plates help to guide the grinder to keep the flats even side to side and from going too deep. Wood blocks the plates are fastened to have a slight amount of swamp.
The barrel blank is held in place by V block clamps on both ends.
V block height is adjustable up and down to provide taper of the flat.
A scrap piece of octagon barrel fits in one V block to serve as the flat index.
It is welded to a full length mandrel threaded on the opposite end. A nut and washer keep it tight. It is kept centered by a turned insert. That's the brown thing between the washer and barrel.
To use all one has to do is set the angle of taper, clamp the blank to the jig, grind one flat, index the blank to the next flat and grind.
Repeat until all flats are ground to shape.
Draw filing and sanding is all that’s needed to finish a new barrel.
Hank
