I picked up some (7) old Bessey K Body clamps a while back on Craigslist. Some of them seem stiff to adjust and I was wondering if and where I should lubricate them (and where not) and with what. One of them doesn't lock when I push the handle towards the bar. I see a hex set screw on the body next to the bar. I assume it needs to be adjusted or replaced? None of my Allen wrenches fit so I assume it is probably metric. Anyone know what size it is? As I said these are the old ones made in W Germany so I'm guessing from the 70's or 80's.