Marking Gauges make life easy

After finishing my latest handplane, a scrub plane modeled on 15th century examples, I had a bit more time in the shop today before I decided I was “done.” While I already own two commercially made marking gauges it’s been a conceit for some time to have one that is actually period appropriate for pre-17th century woodworking.

Detail from Bourdichon’s “Four Estates of Society” (15th Cen) showing what is believed to be a marking gauge on the tool rack.

A marking gauge does one job, and it does it very well. The purpose of the tool is to strike a line parallel to an arris of a board, whether along or across the grain. Usually this is done to assist in layout of saw-cuts, joinery elements, or carving details. Mortising gauges do the same, with two “blades,” to mark for tenons and mortises. Panel gauges are reserved for much larger layout operations.

As I said, having a little additional time today to putter, I knocked one out in about an hour using six tools.

I started with a random block of oak, around 7/8″ thick. I sawed a section that was just over square off the end and started making the fence.

Having my proud block of oak, the real work starts. Using the piece of stock I intended to use for the arm I marked out where the mortise would go on the face of the fence. I then continued the lines around with a straight edge so that the opposite face would have the same layout lines. I used pencil so the line would be more visible in the photographs. Usually I would have just cut these in with a knife. It is important to note the orientation of the growth rings here. The new wood is on the face that will contact a workpiece. Should (when) the wood moves due to seasonal changes, and bend in the fence would cup toward the cutter. This means that even if an Empirical measurement from the pin to the fence at the center of the fence change, the distance from the pin to the arrises would remain square. If I’d gone with any other orientation, there would be no true reference by midsummer to register the tool.

While I seemed to have missed taking pictures of the great hog out, starting by striking the layout lines with a chisel on both sides, working a mortise chisel through both faces toward the middle quickly resulted in a square through mortise. The next step was cutting in the “keyhole” for the parallel mounted captive wedge. What few examples we have, the extants from the Mary Rose especially, tend toward having the wedge run parallel to the arm, rather than perpendicular in later marking gauges. Some would take the time to carefully measure the inside bevel for the key… I rather just eyeballed something approaching a 1-in-6 bevel. That’d be about 9° angle for those using a protractor.

Chopping the key slot was done from only one face, with the bevel of the chisel consistently aimed into the the already chopped mortise. This allowed the chips to fall freely with each pass as I worked to the “back” of the fence. A 3/8″ chisel was used here, so the key hole is minutely larger.

Very slightly here we see where I marked off a cut line for sawing the beam of the new marking gauge. I used a very nice brass and ebony mortising gauge I have kicking around to make the mark. One can also use a knife and a square to get the same result, but the mortising gauge was handier at the moment. This will be the likely duty of the marking gauge in the foreseeable. The gauge was set to the thickness of this piece of stock, so the end result should be square in cross section. A quick rip with a saw and a little cleanup with a spokeshave and the beam was ready.

2013-05-30_16-58-37_242Having an unnatural fondness for Tremont’s headless brads, I fished one out to use as the cutter. Here I’ve already bored a hole through the beam near one end and set the brad through the arm. I had some particular thoughts about grain direction and alignment of the beam, but realistically those matter very little to the lifetime operation of the tool.

2013-05-30_17-12-46_101The wedge is both the easiest and the trickiest part. On one side, it is just a series of compound cuts. No big worry there, a turning saw or bandsaw makes quick work of shaping the wedge. The tricky part is getting the edge that meets with the keyhole to match in angle while being neither too thick nor too thin to mount into the mortise. The chalk shows the general shape for this wedge. Once the rough cuts were made a light trimming with a paring chisel brought the bevel of the wedge to the correct climb and cleared most of the kerf marks. Smooth operation is best in these kinds of tools.

With the sliding part of the wedge in a functional state, now was the time to remove the excess bulk from the rough cutting to bring about a more visually appealing contour to the front and back “locks” that make the wedge “captive.”

And like the wedge, the fence got a beautifying curve as well. Both cases were sawn into general shape then brought to round with a chisel and spoke shave. Using a spoke shave across end grain can be quite a bother at times, but as long as one continues to cut “uphill” on the endgrain, the trouble can be kept to a minimum.

All cleaned up and ready to go. The wedge fits snugly and locks the beam arm in place when set. The benefit of this style of wedge, and it’s orientation, is that the fence can be aligned and set with one hand. It’s slightly trickier than the perpendicular wedges to release, but ultimate convenience takes a back seat on this as it is more important to go for historicity.

2013-05-30_17-46-22_335The excess length of the brad has been clipped off and filed flush with the beam. The business end has been sharped with a fine file to have a slightly ovoid cross-section. The blade is able to equally cut in either direction, and makes a clean line. Every now and again it will need a touch-up to stay sharp, and eventually a new pin will need to be placed in the beam, but the tool is done and ready for duty. If there would be any changes, I think I’ll make the next wedge just a touch thicker. As it is, it grounds out just before the forward lock and it won’t be long before wear from compressed fibers makes it bottom out before locking.

This entry was posted in Design and Proportion, Medieval Tools, Projects, Reproduction, Tool Research and tagged , , , , , . Bookmark the permalink.

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