Tapered Stay V-Blocks
(this is a tool for framebuilders)
These v blocks are designed specifically to be used in a milling machine vise for holding the dropout end of seat stays and chain stays. They also work in a bench vise, and they can accommodate some other tubes as well. One half of the blocks has a rocking pin and allows the blocks to meet the taper of the tube you're trying to hold. You can get really strong clamping force without marring your tubes.
*** Shipping is via Priority Mail. To the USA the shipping cost is included in the price of the tool and everywhere outside of USA there is a $25 upcharge. If you email me I might be able to get you a better international shipping price for countries like Canada that are close, but it will be slower, too. ***