This attachment mounts in place of your router’s factory baseplate and is used for cutting circular disks from, or boring circular holes in, sheet stock. It pivots about a small pin rotating in a blind hole drilled in the center of the stock to be cut. This one is based on a design from Bill Hylton’s excellent book Router Magic.
As much as I like Hylton’s project, I wanted to design a DIY trammel that did not require any table-mounted tools or expensive router bits for its construction. My version is laminated from three layers of quarter-inch stock, and replaces Hylton’s custom-milled T-slot and matching arm with a short piece of aluminum 80/20 rail, which is inexpensively available. The arm can be reversed in the slot to cut small radii, and Hylton’s dimensions have been slightly modified to provide a continuous range of possible diameters of about 2-22″.
Where did you get the pin and the extrusion?
Hi Kevin. The pin came from my local big orange hardware store, and the extrusion from Amazon:
http://www.amazon.com/80-20-SERIES-T-SLOTTED-EXTRUSION/dp/B001F0F0ZY
I’m loving the aluminum shoe. Did you get the sheet from the big box store too?
Thanks. It’s actually cut from an old street sign! But it’s there because I screwed up and assumed the nominal 1/4″ stock I bought at Home Depot was actually 1/4″ thick. Duh, it’s not. So I had to make up the difference with the aluminum plate.
I’m thinking I’m going to do a slight modification to this and just use 3/4″ mdf and route out a dado in it. Thanks for the good plan!
Followup – I think you have put “radius” where you meant to put “diameter” in this section:
“But I eventually decided to cut mine down to 6 inches so that there would be no radius between 1.5 and 22 inches that I could not cut.” Don’t you mean 11″ radius?
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Thanks for posting your router circle jig build. Great information !!!
I am considering making one with a couple of mods to accommodate larger diameter circles. I found some 3/8″ (@ 9.5mm) tall T-Track and will try to use a 3/8″ base layer to keep the router closer to the material. The 80/20 track looks to be @ 20mm tall. The top layer will only go the length of the jig to the router and not underneath it to also keep the router @ 3/8″ (@ 9.5mm) from the material. I would like it to handle some larger diameter circles so will add a few more bolt holes and use 2 T-bolts for locking redundancy (as well as eliminate dead spots in the radius range). Might also make 2 pinned T-Tracks (short and long) out of the 24″ stock length to minimize the overhang when cutting smaller circles.
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