Thread: Parallel Guide Guide

No, that's not an echo ..

All vises have a little play/slop in the screw. This is normal. If there was none then the screw would bind.

Play is a double edged sword – play leads to racking, and racking in a leg vise is desirable when clamping out-of-square pieces. However, racking also then favours one side of the chop over the other, and greater cranking force is required to keep the piece from tipping.



My leg vise uses a wooden screw and has a little play. I was very careful when building the leg vise. Indeed, for those who followed my build, they have seen pictures of the installation (twice – the second when I added the chain adjuster). Everything was square, square, square … and solid.

Very little force is required for sufficient holding power with this vise (about 1/4 turn once the chop makes contact).

When it was new the chop would clamp down squarely and hold with just a little force. No racking. As it wore in, the racking seemed to increase a little, and then the chop began to reveal more clamping strength on one side. In my case there seemed to be a tiny amount less holding power on the “outfeed” side of the vise (the left of the vise in the picture below), which may have occurred as a result of planing edges (i.e. that is where the plane ends and greater downforce is created). This small amount was enough to cause the vise to rack enough to reduce the holding power.



There is nothing worse, as you plane, than the board twisting and dropping down - damaging to yourself and the edge being planed.

I imagine that there would be less play in a high quality ACME metal screw, such as from LN or BenchCrafted. A wooden screw is less precise. I imagine that others experience the same as I do. I’d like to hear if this also affects you. If you are unhappy with this issue, then there is a simple fix.

The problem is not simply the screw, but also the parallel guide. They work together. The parallel guide must also have a tad leeway to avoid it binding in the leg through mortice. Even 1mm of leeway will translate into play in the screw, and from there to the chop. The aim is to get – and hold – everything perfectly square, in such a way that the pressure across the chop is equal, and stays that way.

The fix is at the parallel guide. The parallel guide requires a guide to keep it tracking squarely. In my case, the parallel guide was shifting to the left.

My solution was to groove a section of hardwood that the guide could run through, and add in adjustability so that the exact support could be dialled in. (Note: the parallel guide floats above the PG guide. It does not rest on it).

Your set up would look like this if your parallel guide is built the same way as mine. (Note that the groove/mortice in mine is not centred – not to worry. In my case this does not matter. I was testing out the idea, but it worked so well that I have left it as is).



Simply slide under the parallel guide (as in my case). If you cannot do this, there are other ways to build a fence that keeps the parallel guide tracking square.



Adjust for squareness, and you will find that the amount of force to clamp work decreases significantly.

Regards from Perth

Derek