Need Help with BenchCrafted Wagon Vise

[Izzy Charo]

Hello, I'm installing this vise on a Roubo bench... the issue I'm having is that the wagon runs smoothly in the slot, until I fully tighten the "collar" on the outside...at that point it hangs up badly. I've tried shimming both the left and right side of the collar and no luck. Everything is fine until that final quarter turn to snug up the collar, and then the wagon won't move. Something is out of alignment, but I can't figure out what.... Any help would be appreciated! Thanks!!

[James Jayko]

A video and / or pictures would probably be helpful here.

How is the fit between the guide rails and the plate? My first guess with no other info would be that there could be too much play (ie the rails are too far apart), and when you crank down the vise the plate is canting just enough to hang it up? If it runs in and out smoothly I'd guess the nut block is probably fine?