Originally Posted by
oneclick
That spacer idea will only work if you have a spacer exactly the same size as the cup you're trying to grab - another cup would do, but there is a better way:
You need a large bolt & nut, and two appropriately sized stout washers. One washer goes inside the cup, the bolt goes through that, put the frame in the vice and clamp the flats. The bolt should hang down between the jaws, take the other washer (which is big enough to span the gap at the bottom) under the jaws and put the nut on and tighten it. This way you don't even need to tighten the vice as much - you're not using the clamping force of the vice jaws to hold the frame in place.
I know how it works, I never do it that way, have my own method that works way better for me, see post #2.
Been a mech/tech all my life, fomoco + ASE Senior Master tech for 25 years, 20+years drag racing motorcycles, lots of time spent wrangling and solving problems at work, home, on the road, track and everywhere in between.