Ever since building my own Split-Top Roubo Workbench, I have been interested in the clever ideas people come up with in terms of hardware alternatives. Matt Armstrong came up with a solution using a steel shaft and a linear bearing that once setup, requires no adjustment. Let’s check it out! — Marc
There are a variety of mechanisms and means to get a leg vise to clamp firmly. All of them, in one way or another, restrict the range of motion of the bottom of the chop in order to increase the force applied to the top of the chop. While a parallel guide and pin are a fine way to approach the problem, they require pin changes to accommodate differing material thickness along with additional complexity in construction. Furthermore, unless you use roller bearings (such as the “glide” system from BenchCrafted, pictured left), you have a fair amount of friction and/or slop to overcome in the mechanism. Alternatives to the parallel guide and pin are numerous – some are highly mechanical in nature, featuring chains, sprockets, gears, cams, and so on. Some of you may also have seen that Benchcrafted is reviving the St. Peter’s cross, a simple scissoring mechanism that keeps the chop parallel to the leg.
My design is nothing more than a hardened steel shaft and a linear bearing. Simple to design, simple to implement, and simple to maintain. I used a 30mm linear bearing and 500mm long shaft which ended up setting me back around $60 for the pair.
A hole was bored into the leg vise chop at a 1 degree angle (more or less) so that the top of the chop is tilted slightly forward. The hardened steel shaft was roughed up with sandpaper and then I used polyurethane glue to secure it in the chop. Another hole was bored into the leg for the linear bearing. The hole for the 1.25″ threaded rod and acme nut was match drilled once the bearing was installed, and then the rest of the steps are like any other leg vise installation (secure the nut to the back of the leg, attach the handwheel to the threaded rod, etc).
How does it work? Amazingly. The linear bearing not only restricts any out-of-parallel racking from clamping pressure, but supports and aligns the entire chop so that its motion is buttery smooth. Best of all, it was cheap and elegant. I saved a decent amount of money and, for once, time. I actually think it looks fairly cool, too!
The precision shaft, acme rod, and acme nut were McMaster-Carr purchases. The linear bearing came from vxb.com, and the handwheel was a splurge- a Kipp from Germany. I used a single sae841 thrust washer between the chop and the handwheel, and a roll pin to secure the handwheel to the rod. Lastly, to keep the threaded rod from binding, I put a bronze bushing inside the leg, similar to the function of the acetal block that benchcrafted sells. It wasn’t necessary, but it makes the mechanism even more precise.
Here are a couple videos of Matt showing off his new vise.
Matt Armstrong is a Wood Whisperer Guild member hailing from the SF Bay Area who is a full time husband, new father, and software release manager. He has butchered thousands of board feet of wood in his garage shop and spends more time building shop furniture than working on the projects he promised his wife he’d do.