Better clamping repeatability

This is an excellent bit of advice and opens the door to additional observations. I’ve watched a few videos of WEPS users at work on this site and believe that most don’t really understand the principles of the vise mechanism.

The designer intended that the top screw (the clamp screw)is used to set the clamp distance (the opening between the jaws), and the lower screw (the jack screw) is used to create the very high clamp force required.

To avoid excessive wear and galling of the threads, the clamp screw should be used only to apply enough force to position the blade. The jack screw is used to create very high clamping force by means of the lever principle. Think of this as a common pliers. The clamp screw is the pin (fulcrum). You apply an amplified force to the workpiece by applying force at the far end of the handles.

Keeping this in mind, there is no need to apply more force than necessary to the clamp screw. Except for very large blades, it needn’t be tightened more than snug – just so the blade stays put.

The jack screw is capable of producing oodles of clamp force with only a modest amount of torque. For most small-to-medium blades only about a quarter of a turn past the point of contact is required. I believe this is also what is recommended by WE. If you apply too much torque, you are applying excess bending stress to the opposite jaw. Remember that every extra 1/4- turn bends the clamping jaw that much farther.

The threads in the aluminum alloy clamp aren’t intended to endure the very high frictional (galling) forces created when high amounts of torque are applied to the screws. Moving a hard metal across the surface of a softer metal at high pressure results in galling, where bits of the softer metal are torn from their natural positions. This is often what happens when you “strip” the threads of an aluminum block. Extend the life of your vise by using only the required amount of screw torque.

I suggest also that you lubricate the screw threads with some anti-seize grease. I use RCBS re-sizing lube.

The points in this post are so good, it’s always stuck with me, so I thought I’d bounce it back up. I went thru a phase where I was over-tightening the screws, especially the top one. Now I just use two fingers on the top, just enough to lightly hit the blade, then switch to the bottom. It amazes me how little it takes on the bottom screw to lock the blade in place… especially compared to when I was tightening the top down a lot, doing this makes the bottom screw MUCH LESS effective.

Good description by tcmeyer… if you find you’re battling the screws, this is probably the answer.