Nice job with the inserts. Can you put up a picture of the guide you are using for cutting the triangles?

How do you accurately cut the triangles with a router?

Thanks for the explanation as to how you cut your inserts accurately using a wooden template. I did something similar except I 3-D printed my templates proportionally larger than the inserts. Then, I used a base plate on my router that has a collar which fits into the template. I’ll see if I can come up with a couple pictures.

One thing to be wary of when using a 3-D printer template is heat buildup. The plastic goes soft at about 200 C so you have to make your cuts shallow, about 2mm per pass.

I am using a 1/8 inch bit which helps. As do the vent holes blowing air down into the cut. Also, between passes, I pull off the trim router and blow out the hole to get out retained chips which caused air not to circulate and heat build. Certainly it is an imperfect solution But it beats trying to get the playfield on a CNC table after prototyping has already started.

In my case when cutting non circular inserts I use two templates. One for the larger partial thickness (outer) hole one for the smaller through hole. The templates can either be lined up by eye or be printed to snap into a larger mount that tapes to the playfield.