Converting the Outline to a Pantograph Template

In the process of cutting a matrix for the 18-point @ I made up to go with Swing Bold, I need to make a template to run the pantograph tracer against. The edge of the template has to be high enough that the tracer is unlikely to lift up and go over the edge. This can happen because the tracer tip will be slightly rounded and while tracing the pattern I might accidentally lift the tracer a bit. The top edge of the template might have a bit of a chamfer or radius as well. If the tip is raised enough the rounded edges will conspire to lift it more until it pops out.

This can be avoided if I constantly press down on the tracer but that is tiring and wears the tracer. Ideally the tracer is not touching anything unless you are against the edge of the template.

One other consideration is the strength of the template material. In order to get the spindle to cut the matrix, some lateral force must be applied to it, and this is generated from the lateral forces the user applies to the tracer tip. The force the user applies is multiplied by the reduction ratio of the pantograph, so for instance when doing a 10:1 reduction, a 1-pound (-ounce, -Newton, -whatever) push on the tracer will produce a 10-pound (-whatever) force on the spindle, barring friction in the pantograph mechanism.

Depending on the matrix material, cutting depth, spindle RPM, and cutter geometry this sets a lower bound on how hard one must push the tracer to get anything cut. When the tracer runs into the edge of the template it stops, and cutting stops, so all the force must be resisted by the tracer against the template. If the template is too soft the tracer will dent it. Of course, the tracer is blunt compared to the cutter thus giving a lot of leeway, but generally there are limits on how much softer a material can be used for the template relative to the matrix being cut.

In the film Making Faces the late Jim Rimmer showed his methods for cutting a matrix. His overall workflow from concept to matrix started with sketches on paper. Using the Ikarus font design program for the Mac, he would enter points from his sketches with a digitizer puck, and clean up the contours on the computer. The outline would be printed at 30× enlargement directly onto Bristol board or heavy card stock and cut out with a sharp knife. He would glue this to a board using PVA glue, and dry the assembly in a nipping press. Using this template he would do a 2× reduction cutting the outline into a slab of type metal, and from that he would to a 15× reduction onto the actual brass matrix. He used two different pantographs for the two reduction steps.

The explanation for this two-step process isn’t really delved into, but I suspect that the idea is that the hardness of the type metal is intermediate between that of the brass and of the Bristol board. Trying to cut a brass mat directly from the Bristol board template would probably destroy the template, especially if one wants to make multiple passes (e.g. a rough cut with a large bit not quite to full depth, then a finish cut with a fine bit to finish depth). On the other hand, cutting the type metal from Bristol board would be a single-pass operation and would require less force on the tracer so the template would last. The type metal template then is hard enough for use in cutting the brass matrix. If you want more than one matrix (one for a friend, or one scaled to a different size) the durable type-metal would be re-used, rather than the fragile cardboard one. Even when doing this two-step process Jim said in the film that one had to be careful to avoid “bruising” the cardboard.

I have a stereo caster which I could use to cast slabs of type metal like Jim used, but with the mould spacers I have the slabs would be type high and very heavy. Audrey suggested using the laser cutter at KwartzLab to cut a template from something like 1/8″ MDF. If I do that I also have to account for the thickness of the laser kerf but again that can be done using an oversize tracer once I measure the kerf width. What I might start with is Bristol board reinforced with a non-water-based varnish (water-based products would distort the Bristol board) or perhaps epoxy cement, mounted on a spacer to provide positive engagement for the tracer.

In any case I can think about templates for a while because before I have need for one, I have to make some cutting bits more suitable than the ones that came with the pantograph, make a tracer tip of a suitable diameter, and make some blank matrices.

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