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How to make a circle cutting jig fully adjustable quick and simple

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Blog entry by BenhamDesign posted 08-26-2019 03:09 PM 1337 reads 1 time favorited 4 comments Add to Favorites Watch

I needed a circle cutting jig for a project, and decided I wanted to make one that is adjustable to whatever size I needed, I also wanted one where I didn’t have to drive a nail or screw into my work as the pivot point. It works great and was relatively simple to build out of scrap plywood laying around the shop.

Watch how I built it on YouTube

It has incremental swing arm, a non-destructive way to attach it to your material, and is fully adjustable to dial in the exact radius you want.
So to get started I ripped a strip off some scrap plywood to act as the swing arm. You can make this strip as long as you want to make as big of a circle you. For this jig, I am about 2 feet long.
I do have a sketch on my website if you want all the measurements.
I marked down the center and laid out 1” increments.
I head to the drill press to drill ¼” holes down the length.
Then I used some ¼” plywood and cut a perfect square and marked the center.
I used a forester bit to counter sink for a T nut and switched out the drill bit to drill the through hole.
I positioned the T nut over a dog hole and drove it home.
I’m sure I could get a shorter T nut that wouldn’t stick through, but this is what I had on hand and I didn’t want to drive across town for a 50cent piece, so I just filled the points flush.
To make room for the shaft of the T nut, I just ran a dado down the center of the swing arm.
I should mention that your pivot point plywood should be about the same thickness as your base plate. It will make assembly a little easier
I ripped of a piece of scrap plywood to start making a bracket to attach the jig to the router.
I measured the distance between the holes on my router.
Drilled some through holes
Did a test fit and marked the length so I wouldn’t have a bunch of extra material sticking out, and cut it off at the chop saw.
Then I counter sunk for the heads of the bolts, this would have been easier before I drilled the through holes, but I’m just making it up as I go.
I got another scrap of plywood and marked the width I by holding it up to what I had already made. I did this without the base plate attached
Then I marked the length and cut it off at the chop saw.
I pre drilled some screw holes to attach it to the swing arm, and flipped it over to pre drill some holes to attach it to the mounting block I had made earlier.
I then glued and screwed it to the swing arm.
I then glued and screwed it to the mounting block in the router.
The bolts stick out about a 1 ½” so you can a little over an inch of adjustability between the pivot points drilled in the swing arm.
To locate the jig on your work piece, I line the points up with my layout lines, mark the perimeter so I know where to put the double stick tape, and stick her down.
I pick a pivot hole close the size I want, and while I am there, I marked out the radius in inches along the swing arm.
Then using the bolts, I fine-tuned the radius to my layout line, and cut the circle.
Stay tuned, my next video will be of the round table build.
If you want to see what I have coming for future video, give me a follow on Instagram, and of course. Like, subscribe and hit the bell to be notified when the next video comes out.

Thanks For watching
Brian Benham

-- What I do in and out of the shop at http://www.BrianBenham.com



4 comments so far

View Redoak49's profile

Redoak49

4141 posts in 2469 days


#1 posted 08-26-2019 09:10 PM

Nice!y done video.

View ToughCut's profile

ToughCut

71 posts in 2087 days


#2 posted 08-27-2019 01:37 PM

Like it nice and simple, great video also

-- If you are not willing to learn, No one can help you. If you are determined to learn, No one can stop you.

View BB1's profile

BB1

1439 posts in 1329 days


#3 posted 08-28-2019 01:47 AM

Nice video and great jig! Thanks for sharing.

View pottz's profile

pottz

5978 posts in 1465 days


#4 posted 09-06-2019 05:16 PM

great video brian i always love seeing what ever you do.

-- sawdust the bigger the pile the bigger my smile-larry,so cal.

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