Introduction: Workbench Board Jack

A support for large workpieces when held in face vice.
I had planned to make the standard board with holes and a peg. I had cut a board, but while thinking about how to configure the holes I was playing with one of those cheap guide clamps when s better idea hit me - use the guide clamp to make a jack that can be easily set to any height.
Note that I haven't given dimensions because I expect lots of variation in workbench and clamp sizes. You'll have to work out the dimensions, but its worth the effort.

Step 1: Modify Guide Clamp

Shorten guide clamp to height of bottom of your workbench apron. This entails first taking the ends off the clamp any cutting off the rail and bar with a hacksaw or angle grinder. Next re-thread the end of the bar and swap the ends of the clamp round, because the clamp head will be part of the board jack base. Also drill pilot holes vertically through the sides of the clamp head to attach the foot and jack plate with screws.

Step 2: Make Foot

Cut a u shaped foot out of a bit of scrap 18mm plyboard. The slot is sizes to fit around the clamps aluminium extrusion.

Step 3: Jack Plate

Cut a hole in a piece of ply. The hole must first snugly around the clamps aluminium extrusion. I cut mine a bit small and filed it till it fitted.

Step 4: Top Rail

The top rail consists of two plywood leg brackets, which will be screwed to the workbench legs, an 8mm bar with threaded ends (I don't like threading bars either) and a bracket with a tube as a rail runner. I made the bracket by he
ating up a piece of cut to size plastic guttering and moulding it around the cut off aluminium extrusion from shortening the clamp. The 12mm tube is attached by drilling holes in the bracket and hot gluing (proxy resin would work too) in place. Two threaded 4mm threaded holes in the bracket will attach it to the top of the jack.
By the way its amazing what you can make with guttering a best gun and a glue gun and guttering is free from local skips.

Step 5: Assembly

Assemble the jack by screwing the base to the bottom of the guide clamp (the static clamp face), screwing the jack plate to the moving guide clamp face and bolting the leg brackets and runner together.

Step 6: Installation

Attach the rail to the top of the jack and screw the leg brackets to the workbench. The jack can now be set to any height and width on the rail.

Step 7: Conclusion

This was really an experiment and I was prepared for it not to work, but the jack works better than I had hoped. It provides a solid flexible base to support larger workpieces.