Custom 45° Triangle Quilting Ruler

Mary’s current quilt project has a corner design with an essentially infinite number of 45° triangles, which another custom ruler will simplify:

That’s the end result of several iterations, proceeding from doodles to sketches to increasingly accurate laser-cut prototypes:

A “ruler” in quilting parlance is a thing guiding the sewing machine’s “ruler foot” across the fabric (or, for sit-down machines, the fabric under the foot) in specific directions:

That’s a practice quilt on scrap fabric: quilters need prototypes, too!

The foot is 0.5 inch OD, within a reasonable tolerance, which accounts for the slot width in the ruler. It’s also intended to run against 1/4 inch thick rulers, which accounts for the thickness of that slab of acrylic.

The engraved lines & arcs are on the bottom of the ruler to eliminate parallax errors against the fabric, so the bottom is upward and the text is mirrored for the laser:

Although fluorescent green acrylic may have higher visibility, clear seems adequate for the fabric in question:

I very carefully trimmed the arcs against the ruler outline using LightBurn’s Cut Shapes, which turned out to be a Bad Idea™, because the high-current pulse as the laser fires causes a visible puncture wound at the still-to-be-cut edge:

Those are not straight lines and the plastic isn’t bent!

A closer look:

The arcs without wounds started from their other end and stopped at the edge, which is perfectly fine.

The wounds are unsightly, not structural, but the next time around I’ll extend the markings a millimeter beyond the edges into the scrap material.

The overall design looks busier than it is, because I put different features on different layers in case they needed different settings:

The LightBurn SVG layout as a GitHub Gist: