jig for octagon barrels

Does anyone have any ideas for a jig for holding a barrel while milling it octogonal?

I have used my Forester scope mount drilling jig for fluting barrels but something more substanshall is needed for this I think?

My mii is a 9-42 bridgeport.

Straight octagonal or tapered octagonal?

I've done two octagonal barrels; one using the end of an end mill and the other using a large helical mill (as used on a horizontal mill) on an R8 arbor in my Bridgeport. In both cases, I supported the barrel between centers using an indexing device and a footstock. When cutting with the end mill, I placed screw jacks underneath the barrel to provide intermediate support. When using the helical cutter, I clamped a couple of angle plates to the table to back up the barrel.

The end mill left more prominent tool marks (across the flats and deeper) but seemed to produce a straighter cut; the tool marks from the helical were less prominent (along the flats) but the cut seemed to be more wavy.

[This message has been edited by GGaskill (edited 03-03-2004).]

http://www.gunmaker.net/octagon.html

I have done a couple on my B'port. I used an indexable homemade end mill.

The formula for calculating flats is in Machinery's Handbook.

Mike

What a great site! Some really neat articles there.

Thanks for that!
Dave