February 11, 2014

Moxon Twinscrew Vise

Back in December Enco had a deal on acme threaded rod and nuts that pushed me over the edge to build a Moxon twinscrew vise. The hardware doesn't get much cheaper and this seemed like a good little project to force me to get out into the freezing shop for an hour or two at a time. My friends Lon and Mark joined in to make this a group build and we pooled our order to save a few more bucks on shipping and to take advantage of the fact that each 36" acme rod can be cut down to build two vises. In the end we paid right around $20 for each kit consisting of a pair of 3/4"x9" rods and a set of 6 nuts. 

We ended up following the basic design outlined in the plans that Benchcrafted provides for their much nicer but also much more expensive hardware.


The design is based on 8/4 thick stock so I picked through my stack of oak 2x12's and found one that would yield the 6"x24" and 6"x32" pieces needed for the vise jaws as well as a shorter square piece for the back support piece. Breaking down and milling this stock in the unheated 20 degree shop wasn't ideal but cold woodworking is better than no woodworking.

The only real design challenge during this project was figuring out what to do for the handwheels that operate the vise. The Benchcrafted kit comes with some really sweet cast iron wheels but since we were doing this on the cheap we looked into a few other options. We considered ordering some basic handwheels from Enco or Grizzly and drilling and tapping them to match the 3/4-6 acme threads but it turns out acme taps are really expensive. In the end we settled on using extra nuts with wooden wheels for handles.

I setup a quick circle cutting jig out of a scrap of MDF with a nail through it and then moved on to prepping two 5"x5" square blanks. I drilled a small hole through the blank to center it on the jig and also to center the other holes that will be drilled later.

I found out by trial and error that the circle cutting jig worked much better if I rough cut the circle free hand close to the final diameter and then cut the last 1/8" or so on the jig.

I eased the edges of each circle with a chamfer bit in the router. It may not be a textbook technique but since the pieces were small I ended up clamping the router in my leg vise and using it like a mini router table. I was very careful and tried this out with some scraps first. In the end it worked well and wasn't half as scary as it looks.

I missed pictures of the last few steps to complete the handwheels but it was pretty straightforward. I drilled a 3/8" deep 1-1/4" hole that with some chisel work will house the nut, then drill the rest of the way through the wheel with a 3/4" bit to create the clearance hole for the acme rod. After chiseling out the mortises for the nuts I epoxied them into the handwheels.

We ended up getting together in Mark's heated shop to work on the rest of the vise. We started by marking the center locations for the pair of holes in the front and back jaws and then again drilling the larger hole for the nut followed by a 3/4" clearance hole for the rod in the back jaw and then an elongated 3/4" clearance hole in the front jaw. The elongated hole in the front allows the jaw the freedom to rack diagonally which makes opening and closing the jaw easier and also allows the vise to clamp odd shapes.

Above you can see the corners of the nut knifed in ready for chiseling and below you can see the end result with the nut fitted into the jaw.

The next step was to glue the back support onto the rear jaw. Once the glue was dry I planed the two pieces flush to ensure the vise sits flat and stable on the workbench.

I elected to cover the inside of both the front and rear jaw with leather and ended up finding a perfect 12"x24" leather split on eBay for about $13 shipped. I cut the pieces to rough size and then glued them on with contact cement.

I sandwiched the the vise together with a piece of waxed paper between the two leather faces and used the handwheels as well as a few extra clamps to apply the pressure needed to get a good bond.

After a bit of planing and sanding I finished the vise with two coats of a blend of equal parts oil based poly, boiled linseed oil, and mineral spirits.

The vise clamps down to the edge of the benchtop with a pair of holdfasts on the back support. I am very impressed with how firmly the vise grabs with just a small turn of the handwheels.

I wasn't sure how well the cobbled together handwheels would work but in the end I'm pretty happy with them. The wheels operate smoothly and can be run in or out quickly with a few spins.

This was a fun little winter project and I am looking forward to putting it to work once we get some warmer weather. It will clamp boards up to 24" wide and the fact that it raises the work about 6" off the benchtop surface will eliminate or minimize the need to hunch over to saw or do other detail work.