Portable Workbench Build Process

11/3/2021

Last night I spent some time making a CAD model for the vice mechanism. I'm glad I did as I realised that I hadn't left enough space for the lock piece when it is disengaged. I'd obviously had a brain-dead moment when I was measuring the prototype and only measured it in the locked position. D'Oh!

Anyway, with a lot of playing around and tweaking dimensions, I've got it to the point where I think I can still fit it into the same overall envelope (100 × 80 × 60 mm). I'm going to make the frame out of 80 × 6 mm EN3B mild steel (as it's what I've got), so I didn't want it to be bigger than 80 mm deep. The dimensions of the various lock pieces are sufficiently different that I'm going to make another prototype of the lock piece rather than diving in and making three of them in one go. If it works I can use the new lock piece in one of the final mechanisms; if it doesn't work I won't have wasted as much steel!

The problem with the new design is that the shaft hole had to move up relative to the vice mechanism body, which means the vice mechanism body has to move down relative to the vice jaws. That's not in itself a problem, but it means that there's much less wood underneath the vice mechanism on the foot. At the standard vice end of the workbench, it doesn't matter as that bit of wood isn't doing very much, but at the dual-screw vice end, I was concerned that it might be a bit too thin for the feet to properly support the bench. In reality it might not be a problem as the foot will be glued to the fixed jaw, but to make it a bit stronger on the edges, I decided to add a couple of dowels on either side:

The picture above shows the model of the vice mechanism in the position it will sit when the vice is locked (the view is shown from the outside, with the two jaws of the Moxon vice hidden, so the shaft would be turning clockwise to lock).

The picture below shows what it will look like fully unlocked:

You can see that the overlap between the vice mechanism and the rail is much smaller than it was in the earlier models. I haven't decided yet whether I'm going to cut out a bit of the rail (as in the previous design) or cut out a bit of the vice mechanism.

I'm going to finish drilling all the various holes in the bits of beech before I get started on remaking the lock mechanism (so I don't have to change the milling machine set-up), but I won't enlarge the cut-outs for the mechanism until I've tested the new lock mechanism design. One benefit of the new lock design is that all of the parts of the mechanism (apart from the cut-in-half nut and the cut-in-half tube) can be made out of 10 × 16 mm steel bar; the previous version had three different sizes.

Here are a couple of views of the model of the whole workbench (minus the top) updated to include the vice mechanisms:

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