Marking gauge

This marking gauge is handy to have at hand whether you are laying out joinery, using it as a depth gauge, or simply using it to transfer a measurement to another location.

This marking gauge is handy to have at hand whether you are laying out joinery, using it as a depth gauge, or simply using it to transfer a measurement to another location.

The Fence

This gauge uses purpleheart for the fence and quartersawn white oak for the shaft. Choose a hard wood that works easily without excessive chipping or tear out for the fence blank. After machining the blank, it is re-sawn and glued together to form the mortise for the shaft. Keep this in mind when selecting your wood and try to choose a species and cut that will hide the glue line when completed. The dense straight grain of purpleheart serves this purpose nicely.

The three pieces that make up the marking gauge are relatively small and working with small pieces on power tools raises additional safety issues. To reduce the risk, use a longer blank than necessary to machine the parts for the fence. This will enable you to make several gauges – a couple for yourself and several for gifts. You could alternatively make up a jig to hold the small pieces.

• Mill the fence blank (A) to be perfectly straight and square. Square up both ends at this time, the actual length is not crucial.
• Set up a 3/8″ Onsrud bit in a table mounted router. Place the fence so there is a 1/8″ gap between the bit and the cutter. Raise the cutter to project barely 1⁄16″ above the table. Use a feather board to maintain constant pressure down against the table and against the fence.
• Make one pass along the length of the board. There should be a 1/8″ strip of wood remaining at the edge of the piece. This is a runner that keeps the board level during subsequent passes.
• Move the fence back and make another pass. Keep doing this until the groove is 5/8″ wide.
• When the last pass has been completed, raise the bit to project 5⁄16″ from the top and make another pass.
• Move the fence 1/4″ toward the bit and make one more pass. This will result in a 5⁄16″ x 5/8″ groove running the length of the board.
• Use a table saw to rip the runner from the edge of the piece.
• Using a mitre saw or a cross cut sled on a table saw, cut the two pieces that make up the fence from the blank.
• Glue these two halves together to form the fence with a perfectly square mortise through the middle. Pay attention when applying the clamps – the glue acts as a lubricant and the parts will tend to shift.
• Drill a 1/8″ pilot hole through the fence over the compression gap.
• Counterbore one side to accept a 1/4-20 threaded insert. Drill only as deep as needed for the insert.
• From the other side, drill a clearance hole that will accept a 1/4″ threaded rod.
• Ease all of the corners around the perimeter of the fence, and even out any irregularity at the glue line. Ease the edges of the face slightly but leave the edges of the mortise as they are.

The Shaft

• Select stock for the shaft (B) that is dense, wears well and is straight grained for the best results. Using a jointer and thickness planer mill the material so that it fits tightly with the mortise in the fence. For the gauge to work smoothly, the shaft must fit tightly and be perfectly straight.
• Cut the shaft to length.

Hardware

• The marking point could be any hard piece of metal that you have shaped to an appropriate point. A piece of bandsaw blade makes an ideal marking point.
• The blade is held in place in a groove on the shaft with a screw on either side. Drill clearance holes for the shafts of the two 8⁄32″ brass screws. Counterbore one side to the minimum diameter of the corresponding nut to a depth equal to its thickness.
• Place the nut over the counterbored hole; use a very sharp pencil to outline the nut.
• Use a sharp chisel to remove the waste and allow the nut to be fully recessed. This should be a snug fit.
• Use a band saw to cut the compression groove into the end of the shaft.
• The easiest way to cut the small notch to hold the blade is to use a scroll saw blade. A fret saw will work equally well here. The object is to carefully saw a kerf at right angles to the compression groove between the screws that will hold your metal point snugly. This should be just deep enough to allow the point to fit in place.
• Insert the point.
• Insert the brass nut into each of the counterbored sockets and use flat head brass screws, countersunk flush with the surface, to clamp it in place.
• For the fence adjustment knob (C) you will need a 1″ square piece of purpleheart. Connect the diagonals to find the center and drill a ¼” diameter hole ¼” deep.
• Cut a piece of ¼” threaded rod to length and chuck it into a drill press. Turn the drill press on and use a file to chamfer the leading edge. This will make it easier to engage the threads in the insert.
• Epoxy the threaded rod into the hole in the purpleheart. Using a sander or wood files, shape the knob to what ever you find to be a pleasing and easy to use shape.
• Insert the shaft into the fence and fasten the fence in place with the knob.