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Circle Jig for a Router

Sean Wright

Sean Wright

Member
Messages
902
Location
WNY, Buffalo Area
I have been working on a shop built air cleaner/filter. In order to cut the circular holes in for the fan, I had to build a circle cutting jig for my router.

Basically it is just a piece of plexi-glass that I mounted to the bottom of the my plunge router. It has a hole for the bit, and then holes for a pin (I'm using a nail with a gound down point). The holes are spaced so that when using a 1/2 in bit it will cut a circle (outer diameter) from 6 in to 25 in. I made it so that I can add additional holes in the future if the need arises. I wrote the increments on the plexi-glass, along with the size drill bit to use for the pin hole. I then taped over the writing with clear duct tape so that it won't wipe off.

Very basic, but it does the trick. :thumb:
 

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Looks real nice, Sean. I needed to cut some smooth circles a while back, and made something similar to yours, but I didn't have any plexiglass. I ended up using a scrap of pegboard, then making a hole for the nail wherever I needed it (I didn't use the pegboard holes). I was surprised how well it worked. Yours is much nicer and more permanent. :thumb:
 
Frank Fusco said:
What kind of bit do you use in the router? I've tried spiral cutters with zero success.
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Frank,

It is a straight 1/2in carbide bit, with a 1/4in shank. I would prefer to use a 1/2in shank, but I don't have one yet. The circle that I cut was in 3/4in pine plywood and was 11in in diameter. It took several passes, with the bit a little lower each time to make the circle. I have never used a router circle cutting jig before this. I was suprised as to how easy and well it worked.
 
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Very nice. That is one of those things that come in so handy when the need pops up. That's what I like about the jig section here; I come across something I'm trying to do and say "oh, so-and-so had a jig for that on FWW" and I can go find it.
 
I also made one a year ago for cutting the holes out for the blast gates. I used a piece of 3/8 plywood. Not pretty, but very functional. I found I needed to put 3 screws through the cut out part to something underneath, and also anchor down the piece I was keeping to keep from ruining it when I got to the end of the cut. Jim,
 
Jim O'Dell said:
I needed to put 3 screws through the cut out part to something underneath, and also anchor down the piece I was keeping to keep from ruining it when I got to the end of the cut.
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Here's a little trick I learned long ago when cutting circles with the router;
Take a couple of pieces of scrap 3/4" or so wide and hot glue them to the underside spanning your circle. Just a couple of dots, one on each end and one or two in the center of the circle to hold it in place when you finish the cut. Works great to save either piece, the inside or outside depending on which is your "good" piece. The hot glue holds strong, but pops right off when you're done and doesn't leave any holes.
Mike

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M Toupin said:
Here's a little trick I learned long ago when cutting circles with the router;
Take a couple of pieces of scrap 3/4" or so wide and hot glue them to the underside spanning your circle. Just a couple of dots, one on each end and one or two in the center of the circle to hold it in place when you finish the cut. Works great to save either piece, the inside or outside depending on which is your "good" piece. The hot glue holds strong, but pops right off when you're done and doesn't leave any holes.
Mike

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Mike,

Thanks! Thats a good idea! :thumb:
 
I just made one also, but a bit larger, for a Triton. I needed a 41" and a 42" radius for bent lamination master forms. I had some 3/16" drill rod about, and used it for the pin. Strong and tight. Just a thought.
 
That is a good idea Mike. On the blast gates, I just used the holes where I would be bolting it together with it's mate to anchor it down, so no unused holes. In fact, when I cut the holes out, I had bothe sides of the blast gate and the slide all put together so the circles all matched when I was finished. But there will be times when I don't have that luxury. Hopefully my brain will remember the hot glue idea! Jim.
 
Several years ago I needed to build a curved wall for something? It had about a 26' radius. Using this method I was able to cut a 3/4" plywood pattern for the bottom and top plate of a 2x4 stud wall. After one pattern was cut on the 4'x8' piece of plywood I could use it as the pattern for the rest of the pieces. Took some space to lay it all out but it worked like a charm.:D
Shaz
 
Robert Schaubhut said:
Several years ago I needed to build a curved wall for something? It had about a 26' radius. Using this method I was able to cut a 3/4" plywood pattern for the bottom and top plate of a 2x4 stud wall. After one pattern was cut on the 4'x8' piece of plywood I could use it as the pattern for the rest of the pieces. Took some space to lay it all out but it worked like a charm.:D
Shaz
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Shaz,

That was a 26 foot radius?:eek: Must have been quite a build. Do you have any pictures?
 
Sean Wright said:
Shaz,

That was a 26 foot radius?:eek: Must have been quite a build. Do you have any pictures?
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Hi Sean,
You know the motto no pics, didn't happen:rofl: :rofl: :rofl: No photos but I have the remnants of the "arm" or at least segments of it around. It was a matter of creating 1 an arm with no flex over the span, 2 a pivot point that would not move nor release the radius point, 3 elevating the 4'x8' plywood so as not to cut the concrete, 4 make sure the plywood being cut didn't move, and 5 as I remember, creating a relatively smooth path over which the arm needed to move. I'm sure you see how those things in place all would work well.
Shaz
 
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