Trammel with Pencil Holder

thingiverse

A trammel is a tool for accurately laying out large circles and arcs. It consists of two holders for scribers that can be moved along a bar. This design is based off of a design by http://www.thingiverse.com/araspitfire, http://www.thingiverse.com/thing:4206. I wanted a set of trammel points that would work with a 1/4 inch bar and 6-32 hardware. Also, I wanted a pencil for one of the points for marking wood and paper. Note - I would be glad to make a metric hardware design of this if someone wants to test it out. Instructions 1) Print out either two point holders if you want a traditional scriber style trammel, or a point holder and a pencil holder if you want to mark in pencil. 2) The holes for the 6-32 screws should be drilled out with a #27 drill. The hole for the point holder should be drilled out slightly over 1/4 inch, using a 17/64 or size F drill. 3) Use a hacksaw blade to clear out any strings inside the slots. 4) Turn, file, or grind a point onto a 2-3 inch piece of 1/4 inch steel bar. 5) Press 6-32 nuts into the hexagonal cavities and install 6-32 x 1-1/4 round head screws through the opposite side holes. 6) Install point and #2 wooden pencil in holders. Tighten the screws to hold the point and pencil in place. 7) Slide holders onto 1/4 inch square bar. A sharp angled cut on one end of the bar will help to ream out the square holes so that the holders slide freely. Use the screws to lock the holders in position. 8) File the ends of the square bar so they don't cut your hand when you use the trammel. 9) Enjoy your trammel. You can use whatever length bar is needed or keep different convenient lengths on hand.