Probably better using the vise than a hammer, most metals have a
"memory", leave them in the vise several minutes and re-tighten once or
twice.
In the past, I've used small U-bolts successfully. You could also buy
the tool, use it, and then re-sell it on eBay to get some or most of
your money back. I've done that before with tools that I "had to have"
only once, works for me.-Jitney