Routing out a circle with a jig - Need advice please! - Router Forums
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post #1 of 18 (permalink) Old 02-18-2020, 06:19 PM Thread Starter
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Default Routing out a circle with a jig - Need advice please!

Hello all,

It's been a very long time that I've been here, thanks to Hurricane Michael.

I'm going to try routing out a circle in a piece of plywood.

I bought a jig to cut out a circle using my router, which I have never used. It's a Bosch Colt.

I'm not sure how to cut out the circle though.

I know what I'm supposed to do, but not how to set up the cut.

Do I put the wood that I'm cutting on top of something (other than my bench) like a platform?
Do I just clamp the wood to a bench and only cut to the top of the bench then move the piece?

I'm completely router illiterate so be gentle but I really need to cut this circle for a new stand I'm making

I tried to cut the circle with my jig saw and a jig and failed miserably

Thanks in advance
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post #2 of 18 (permalink) Old 02-18-2020, 06:46 PM
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I used one of my plunge routers with a modified circle guide to cut out my 15" sub-woofer mounting holes in 1" thick MDF. That makes a LOT of fine dust, even with a 1/4" cutting bit. I could have gotten away with using a jig saw and circle guide but then I couldn't post it up here lol. Did it in 4 passes/hole.

For multiple, smaller holes (2-5/8" for the new instrument panel on my project car) I bought a Milwaukee hole saw exactly the right size for $12.

Here are some pics (not exactly tutorial style, I think I was afraid to pull the phone out during the dust storm, even though it was outside lol) hope this helps a bit. Need to remember the difference between the center distance from the guide pin to the router bit is NOT going to be the hole size.....need to add the outer radius of the cutting bit.....

Best bet is to secure the piece you're cutting on a solid surface, maybe with some styrofoam underneath the way the track saw guys do it. That may also reduce the dust since it cannot fall below the work area now and be more likely sucked up by the vac above the table.
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post #3 of 18 (permalink) Old 02-18-2020, 08:21 PM
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I have cut out circles using a trammel (homemade). For the large circle for a dining table I had the wood slightly elevated off the benches to allow cutting without worrying about cutting what was underneath. For the smaller ones, I had a sheet of disposable MDF material underneath so that it didn't matter that I cut into it.

It all depends on how you're cutting your circle. Are you cutting a circle out of something like Paul's project above, or are you looking to be left with a circle like my dining table?
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post #4 of 18 (permalink) Old 02-18-2020, 11:08 PM
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Yeah, same question, are you cutting out a circle that you're going to use, or just cutting an opening such as the speaker boxes? If you're cutting a circular piece, you can use a circle cutting jig. You normally would drill a small hole and insert a peg that holds on to the jig. A plunge rounter then makes multiple passes. Since it's a low power router, you will make many light passes and do it without pushing the bit too hard forward.

If you're making some sort of table top, you put the good side down and drill the hole only part way through. Put a tab of tape on the drill bit so you don't penetrate or cause a bump in the middle of the circle's good side.

You do have to work out how to attach the router to the jig. Usually done by taking off the base plate and using it to mark the location of the mounting bolts. Use a punch to mark the center of each mounting hole, it will give you a dimple that will help you drill accurately.

You can use the same small mounting bolds you removed from the base to attach to the jig. If you're using pan head bolts, you can drill slightly oversized holes, then a larger hole part way through so you can position the router on the jig. Here's an over simplified drawing of what I'm saying.

For something like a table top where you're using glued up hardwood, you can use a spiral bit to cut the circle, then put in some sort of roundover or ogee bit to make a nice edge. If it's plywood, you just cut it and use iron on edging.

Once you get started, just take your time. It is really a pretty easy thing to do, just don't try to cut too deep on each pass, usually no deeper than 1/8th inch per pass. The Jig will do most of the work for you. When I do this, I suspend the power cord from something overhead so it stays out of the way. And make sure the center pin is firmly in place. My jig wants a 1/4 inch pin and I often just use an upside down drill bit. If the circle is made of 1/4 ply, I will drill about half an inch deep on the back side.

I am also a fan of using an inch thick piece of insulating foam underneath the workpiece, and clamp the corners down as best I can. You can also use some double sided tape to hold the circle in place. With a couple of strips of tape, if you manage to move it, you're pushing too fast.

Hope this is helpful. These days I cut circles with my band saw, different kind of jig required for that. It's even easier than cutting one with the router. But for cutting a clean circular hole, the router with a spiral bit is the way to go, the band saw won't do that.

Also attached is a picture of four sizes of down spiral router bits. You can use high speed steel for occasional use. Carbide bits are sharper and last longer, but far more susceptible to breaking and heat damage.
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post #5 of 18 (permalink) Old 02-19-2020, 12:40 AM
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You didn't say what you had for a jig Jessie but most pivot on a pin that goes into a hole in the center of where you want the hole. There is one problem with this method and it's the piece left in the center. The moment you finish cutting it out the bit can catch it and start bouncing it around in the cutout. For that reason it's a good idea to put your plywood on top of some sacrificial surface and either use a pin long enough to go through both layers, or brad or pin nail it in a couple of places to the bottom layer, or put a couple of strips of double sided carpet tape under the center piece so that it stays put.
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post #6 of 18 (permalink) Old 02-19-2020, 02:16 AM Thread Starter
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Thanks all - the quick responses are greatly appreciated!

I'm cutting the hole out of 3/4" ply so I can put a bucket inside the hole.

Here is the jig I just purchased

I have some sacrificial foam as well as some plywood I can clamp to my bench - that's what I was missing.

I've not used the router before, and have had it for quite awhile.

I tried doing this with a jig saw and home made jig, but the blade on the saw kept bending giving me a beveled cut. Needless to say it wasn't pretty, nor did it work

I'm hoping I can cut out the bevel part with the router and make a clean circle.

Once I have it done, I'll post the results.

Thanks again - your help is greatly appreciated.
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post #7 of 18 (permalink) Old 02-19-2020, 04:14 AM
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Quote:
Originally Posted by newbie2wood View Post
Thanks all - the quick responses are greatly appreciated!

I'm cutting the hole out of 3/4" ply so I can put a bucket inside the hole.

Here is the jig I just purchased

I have some sacrificial foam as well as some plywood I can clamp to my bench - that's what I was missing.

I've not used the router before, and have had it for quite awhile.

I tried doing this with a jig saw and home made jig, but the blade on the saw kept bending giving me a beveled cut. Needless to say it wasn't pretty, nor did it work

I'm hoping I can cut out the bevel part with the router and make a clean circle.

Once I have it done, I'll post the results.

Thanks again - your help is greatly appreciated.

Hi Jessie,


The circle jig is probably the most common jig used for routers,


There are so many on the market and posted in the forum.




I have at least 4 different versions @harrysin has posted a couple you could make yourself, and the one I use the most...


Simples........( a reference to a TV ad in Oz)
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Last edited by jw2170; 02-19-2020 at 04:15 AM. Reason: spelling
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post #8 of 18 (permalink) Old 02-19-2020, 07:40 AM
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If you don't want to cut into whatever is below then put another layer under the plywood. Or if the piece is big enough you can simply set it on two sawhorses. Use a small straight bit, A 1/4" would do. Take several passes and you will make a nice cut. If you want to bevel it, it should be done after the hole is cut.
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post #9 of 18 (permalink) Old 02-19-2020, 07:43 AM
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The other advantage of having another piece of wood underneath the piece you are cutting is tear-out. You will substantially reduce tear-out on the edges. It will be much easier to cut as well. Take shallow cuts--increasing the depth a little more each time. It will be shocking how easy this is. Also draw out your circle and verify you are cutting exactly where you want to cut before you cut. Good luck and have fun.
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post #10 of 18 (permalink) Old 02-19-2020, 08:13 AM
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make a a torsion grid for the cut table...
size to fit the need...
reusable..
easier clamping...
remember.. the waste center needs clamping/pinning too...

.
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