Thien Router Table Circle Jig
Copyright (c) 2005 Phil Thien
If you want to
make your own Thien Cyclone Separator Lid,
you're gonna need to make circles. Of course, there are all
sorts of reasons you may need to make circles (or holes, this jig
makes those, too). And there are all sorts of ways to make
both. But this jig is easy and foolproof.
jig to make a circle
(1) Drill a
1/4" pilot hole as the center of your circle. (2) Adjust
the jig's pivot to the correct radius for the desired circle.
(3) Use the jig as a compass and (using a pencil) draw an outline of
your circle on the wood. (4) Rough-cut the circle
(leaving about 1/16" of material) with a jig saw or (if you have
one) a bandsaw. (5) Finally, using a 1/2" (diameter)
flush-trim bit in your router table along with the jig, perfectly
finish-trim your circle.
jig to make a hole
(1) Drill a
1/4" pilot hole as the center of your hole. (2) Adjust the
jig's pivot to the correct radius for the desired hole. (3) Use
the jig as a compass and (using a pencil) draw an outline of your
hole on the wood. (4) Drill a 1/2" starter hole just
inside of the pencilled outline. (5) Finally, using your router
table with a 1/4" flush-trim bit (inserted through the starter
hole), along with the jig, cut your hole. NOTE: As
you finish the hole, the center pivot point will be unsupported
which can lead to a ragged finish to your hole. I suggest
inserting pieces of 1/4" dowel in the bit's cutting path as you
progress to keep the middle (waste) centered in the hole.
I realize this
page is short on details but it should provide enough information to
make your own jig.
Detail shot of
the pivot. This was made using: (1) Knob with a 5/16"
threaded hole, (2) 5/16" t-nut (from Woodcraft), (3) 5/16"
brass all-thread that was turned down to 1/4" at the end (I just
chucked it in the drill press and filed the threads off), (4) Some
washers. I will try to add better pics of the pivot shortly.
end of the jig. There is a 1/2" diameter radius in the end
to catch the larger flush bit for making circles, and a 1/4"
radius on the inside to catch the smaller bit when making holes.
circle for one my of Thien Cyclone Separator lids.
shot: The wood is pushed against the bit and spun. The
bearing rides in the jig and creates a perfect circle.
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this design my unique intellectual property, and reserve all rights.
do not take credit for my work by submitting this design to
magazines as a "reader's tip." I realize that this
design will appeal to woodworkers and is something that can be made
If you want to make one for your own use, please be my guest.
If you want to mass-produce them, please contact me first.