Circle Cutting Jig Suggestions

[Larry Fox]

Guys, I need to cut a bunch of circles with varying radii via a router and am looking for jig recommendations. Under normal circumstances I would just make one and move on but or this particular task I would like to have some precise control over the radius. For example - one I need to do has a radius of 7 17/64. The range of radii that I need to be able to cut is probably smallest at 5" and largest at 13". For this task I would like to use a plunge router (PC 7529 to be exact).

Anyone have a recommendation?

Thanks in advance for your time.

[Dan Hintz]

Sounds like a pin mount with a sliding ruler attachment is the best way to go... but I'm not a huge router user, so take it with a grain of NaCl.

[Derek Gilmer]

I've used a piece of hardboard with various holes drilled in it. I just mark the diameter of the hole (inside or outside) for each hole and have had good luck with that.

[Doug Shepard]

http://microfence.com/circle-complete-p-54.html

[glenn bradley]

Most commercial version that I have seen use 1/16" as their smallest increment. A sliding arrangement will probably serve you best. I knocked this together pretty quick and it is continuously variable but, made for the router table or bandsaw.

[Richard Rodgers]

Glenn , that is one very nice jig. And it won't break the bank to make it like buying some of the commercial ones.

[Mike OMelia]

I use a Wells-Karol jig. You can find links to it on guitar forums. Folks will make them for about $75. Use a laminate trimmer.

Mike

[Bob Wingard]

Probably the simplest and most versatile circle cutting jig I've ever seen was known as "The CIRCLE MARK-N-CUT" and it was made by a company in Kentucky. It is no longer available, but is also not real hard to build. The way it is setup is : The body is a piece of LEXAN with a series of 5/8" holes in a straight line and 1" on center. This can be whatever length suits your anticipated needs. At each end are three additional holes ... at one end, they are 1 1/16" on center ... at the other 1 1/2" on center. Your router, equipped with a 5/8" bushing can be dropped into any of those holes, and the only part left is to anchor the opposite end. This is where their "magic" comes in. They used a bronze 5/8" od bushing which has a 1/2" id. The bushing is a snug fit in any of the previously drilled holes, and, as such, can be set to make circles of any radius that would be 1" .. 1 1/16" .. or 1 1/2" in even increments. NOW ... take a piece of 1/2" round material ( I used some Delrin rod I had laying around) and cut/file/grind a small notch on it's outside perimeter and stick it into the bushing. Place a nail/pin into the groove, and now twist the bushing in it's chosen hole, and the entire jig can be moved by the cam action in increments as small as 0.001" By using various hole spacing and dialing in the exact dimension with the cam feature, circles of any diameter can be cut. If anyone is interested in building such a jig, I can get some photos of the components to possibly clarify all of this. Another neat feature of this jig is that you can make another insert for the bushing with a hole in it the exact size of your router bit, and you can view the surface beneath the bushing, and view the exact area that the bit will cut away. Additional inserts can be made to accept pencils/knives/scribes even woodburning tools.

[Steve H Graham]

I had to make a 12" circular hole the other day. I took a long piece of scrap and made a hole in the middle of it. I put blocks under it at each end and clamped it to my table. I stuck the workpiece under it and ran a screw through the hole into the workpiece. Now I had a workpiece I could turn in a perfect circle.

I raised the router bit up into the work at the right radius and turned the work until I had a circular cut. I used a bit with a bearing, and I took more than one pass. When the cut was deep enough for the bearing to engage the inside of the circle, I no longer had to rely on the screw, and it didn't matter if the waste came loose.

The result was the front of this amp cabinet, which I still have not finished!


04 30 11 firefly amp with nearly assembled speaker cabinet.jpg

[Kirk Howard]

http://microfence.com/circle-complete-p-54.html

+1

1/64 accuracy with multiple settings will get pricey. I cut tons of circles, and while I thought my Jasper jigs were expensive at first, their repeatability at 1/16 increments is worth it to me. I also use hardboard home-made jigs, but the screws used to hold them down at the center eat away at the hardboard and I find them moving after only 3 turns. Maybe more careful setup would improve that but I don't think you'll get repeatable 1/64 results.

[Jim O'Dell]

I used a piece of 3/8" plywood, pulled the base off my PC8529, marked and drilled holes then countersunk them so the 3 screws attache it to the router, hole for the router bit to come through. The I drill 1/8" holes as the pivot point. I had to drill about 5 to get the right diameter to be a friction fit on the 6" PVC pipe, marked it so I can go back to it. I use the router bit and a pencil to make a reference point, try it on scrap until I get the right diameter. I can get 15 or so "opportunities" to get the right size, if you know what I mean, before I run out of real estate. This one jig did the 4", 6" ducting for blast gates, plus a 10" hole for a sub-woofer box. Won't do much smaller than 2 1/2", but that size will use a hole saw. If you can build an infinitely adjustable piece down the center of the jig, that would be quicker. It's just a little more involved than what I built. Jim.

[Prashun Patel]

I use the same method Jim says. Trial and error with a cheap base. The only downside is you can't see thru the plywood.

Do you have to cut disks or holes? If you have to cut disks, then (I realize you want to use a plunge router) I submit that you might consider a bandsaw. A bandsaw-cutting jig is easy to make and infinitely variable. Also, if doing a 'bunch' of them, this will be quicker.

[Chris Padilla]

Jasper makes several jigs that work fantastic. google