WoodSkills Issue 02 - Page 54

The screw hole alignment is similar for the front jaw since the 1/8-inch portion overhanging the leading edge of the workbench sits below the surface of the workbench. In the photo below, a six-sided nut is fit into its captive mortise. The extra time spent creating accurate mortises for these nuts is well worth it. The aesthetic of seeing a nut completely housed into the surface is a sign of good craftsmanship. As well, the strength and holding power of the nut in a mortise is second to none. You can go the extra step and orient the face of the nut so two of its points are parallel to the edges of the rear jaw, as shown.

The thickness of each jaw is 1.75 inches, and the thickness of the six-sided nut itself is 3/4 inches deep. This leaves 1 inch of wood in the rear jaw between the inside and outside faces, more than enough to maintain rigidity and strength. Both six-sided nuts are fitted into the inside face of the rear, fixed jaw. This step is easily the most time consuming of the Moxon vise build, but a critical step to get right. The front and rear jaws are dimensioned to be identical in length with the front jaw slightly wider by 1/8 inch. The next step is to test fit the hardware. Once the ACME-threaded screws, large nuts and handwheels fit and function correctly, the build can resume.

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Mortise and bevel-edge chisels are used to hog out the wood for the six-sided captured nut.

The screw holes in the front jaw are elongated from side to side to allow clamping of irregular pieces of wood. Irregular clamping causes one side of the front jaw to not be parallel with the rear jaw. The extra wide screw hole allows the front, movable jaw to move freely along the screw length. This is accomplished by shifting and drilling the front jaw left or right of the main screw hole 1/16 inch on either side. The hole is bored through again with the extra 1/16-inch and precisely elongates the front jaw holes. Avoid elongating the holes in the vertical direction.

Although this step can be performed using a wood rasp by carefully gouging out the left and right sides of the 3/4 in. screw hole, I opted to use a drill press and 3/4-inch Forstner bit. The choice is yours to which method you feel comfortable with. One of two ACME-threaded screws is fitted into the rear, fixed jaw. The mortised nut and rear nut have been installed. There is not much torque necessary to lock the screw down since the front nut is captured in its mortise. The bored screw hole for the ACME-threaded screw is a little over 3/4 inch and the threaded screw is a tight fit. A second screw is installed on the opposite side of the rear, jaw and the front jaw then test-fitted to the rear jaw.

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