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I would like to post this circle cutter I built yesterday in hopes others might find something useful as I have from your designs and hard work building jigs.

I'm no luthier nor a very good wood worker but got sick and tired of my Dremel tool wrecking work and being a general PIA so I decided to build a Circle Cutting jig for my Bosch Colt.

I discovered lots of jigs on the web and on this site and liked the simplicity of a wooden jig, but the micro adjustability of some other designs so I combined both worlds. I haven't mounted the Colt router yet but am very happy with how solid it came out.

I used poplar for the base since it is so soft and oak and scrap walnut for the other parts. All the bottom edges are eased to minimize damage t the guitar top and I was able to get the adjustment down to almost zero back lash on the wing nut adjustment so I hope to be able to creep up on some finer detail with rosettes than otherwise possible with a single wing nut adjustment in other designs.

Also the 2 wing nut hold downs really create a stable pin locator. I have yet to figure out to really get the 3/16" pin set solidly as it is just press fit currently.

I haven't cut a circle yet but will later today and let you all know how it works in practice.

Here's a couple of pics.

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Bottom view, needs epoxy clean-up.



With Bosch Colt Mounted

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Works amazingly well or maybe it's just comparing it with the Dremel set up which I never trusted and could never get a good clean cut.

As I mentioned above the locating pin is just press fit into a 3/16" hole in the oak and it slips in and out and I wonder, from your experience, if this is bad thing?

While drilling a 3/16" hole in a test piece the pin was left behind and I'm wondering if this isn't an OK good way to use the pin? Maybe even locate it first in the test piece then place into the jig? I presume that eventually the hole in the wood would become over-sized but that might be fixable. Anyone else with any experience with press fit pins?

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Larry, you might try making a 3/16" metal bushing and inset it into your jig. That may solve any wear or sloppiness. Just an thought.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

I am far from having sorted out my ideal circle cutting procedure. Currently, I am using a non-powered jig with a blade. To avoid the issue of the top wood wearing too quickly, I tape the top down to a counter top sink cut out with a hole for the pin. The center pin is held tightly by this backer board and the circle cutter. It may not be all that important for a router jig, but I find myself making lots of passes and worried about the hole in the spruce getting sloppy.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

I just did the final cut on my rosette and it worked perfectly. I also have a backer piece under the work piece to anchor the pin. I'll cut the top later today and remember this same tip. Thanks.

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I'll bet I'll have to do something to protect that hole eventually. Maybe epoxy a small nut in there with a 3/16" hole? How else might I get a bushing to stay in there?

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The ability to adjust the dia. with the screw while the router is running is a very welcome feature, rather than removing the base and adjusting randomly and inaccurately.

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Too bad you can't delete your posts once they become superfluous.

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Old growth, shmold growth!

Sorry about that. I keep forgetting that no one else lives in my head. See pics.

Works so so so much better than the Dremel. The two wing nuts really hold it steady and when you want to adjust it even the slightest you can keep the router running, loosen the wing nuts just a little, screw the adjustment screw as little as you need, tighten the wing nuts, and sneak up on a very accurate cut. Nice.

I've decided to keep the pin free and just get a bushing for the pin where it goes into the oak piece on the jig. Looks like it will be a drilled out brass nut, epoxied in. Then get some collet adapters so I can use my smaller bits and should be good to go.

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Nice. Functionally very similar to the Wells/Karol jig that many of us use and, I suspect, just as functional. In my case I have a 1/4" pin captured in the jig and just drill a hole in the rosette, soundboard or whatever I'm working in. No need for an insert in that case.

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Steve Smith
"Music is what feelings sound like"

Yeah Steve I googled circle cutting jigs and came across the Wells/Karol jig and marveled at the ability to micro adjust the dia. I also saw the simplicity of the wooden jigs with the single wing nut adjustment but knew using that single wing nut would be some really difficult trial and error to get things just right when working with tight tolerances which EVERY rosette requires.

This design is obviously a combination of the two designs. Very surprised at how well it works and if you get the center support nuts adjusted just right (they allow the threaded rod to spin freely through that block) there is almost no backlash and a very small turn in the wing nut adjustment screw moves the pin in very small increments.

Was wondering, if I decided to, how to 'capture' the pin in the jig? It's just 1/4" oak that the pin fits in. Thanks.

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I use a double-headed nail for the pin so that you can easily pull it out when you want.
For a bushing,I have used a threaded bushing and drilled out the threads and grind off any excess length.
You might consider a threaded insert and jamb-nut in the first block.

I like the simplicity of the design.

Bob

My pin is just press fit but I'm using a block of UHMW poly that's about 1/2" thick.

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Steve Smith
"Music is what feelings sound like"

Got it - thanks.

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When I used to build speaker cabinets, I had many holecutters, both fixed diameter, and adjustable. All were made from Lexan, and setup to take a router with a guidebushing and spiral bit. Having the ability to hold the router like a steering wheel, and "drive", made this immeasurably easier. All of them were standardized with a 1/4-20 threaded center hole, for cutoff machine screws.

I like the microadjustability of the OP's design.

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larry, that looks like a laminate cutter rather than a plunge router. Do you have any problem starting off getting the cutter into the wood?

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We are all in the gutter but some of us are looking at guitars.

Yeah Joe it is a laminate trimmer and I'm just very careful when turning on the trimmer and am taking very small bites within the context of rosettes. As long as your - not - right on the line of your cut there is little danger of thrashing the material too badly. Once down in the material you can sneak up to the line with the adjustment screw.

I wonder if the Wells/Karol jig has the same problem/feature?

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Same feature but I find it to be easily managed.

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Steve Smith
"Music is what feelings sound like"