I have four pieces of 23 inch diameter 3/4 treated plywood that I need to cut a 12 3/4 inch hole out of the center. I'm thinking of using my router. The disks have a 1/4 inch hole in the center from my bandsaw cutting fixture. Any advice?
[OP]
Contributor
I have four pieces of 23 inch diameter 3/4 treated plywood that I need to cut a 12 3/4 inch hole out of the center. I'm thinking of using my router. The disks have a 1/4 inch hole in the center from my bandsaw cutting fixture. Any advice?
Confidence: The feeling you experience before you fully understand the situation
Contributor
I would build a router circle template.
They sell jigs for this but for this I just do the follwing
Cut a piece of 1/4" plywood roughly shaped like the base of your router with a 5" x 3" wide protrusion
Drill a 2" hole for the router bit to get to the work
Bolt it up to the router.
Drill a 1/4" hole 6- 3/8" from the outside of the router bit that is being used.
Drill a 1/4 hole in the work center
Use a 1/4" dowel.
[OP]
Contributor
That's pretty much what I was thinking. What style of router bit would you use and would you cut the full depth with it? Would cutting half depth with a straight bit and using a jig saw to cut circle out then finishing with a pattern bit be a good idea?Originally Posted by George Yetka
Confidence: The feeling you experience before you fully understand the situation
Contributor
Above posts are what I'd do. If you'll be doing this a lot, I'd purchase a template, but for anything one-off, I'd build one as George outlined.
For bits, if you care about both sides and minimizing tear out, I recommend a compression bit and just make sure to plunge at least the transition depth for your first pass. If you only care about top, use a downcut bit. If you only care about the bottom, use an upcut bit. You mentioned the ply is treated, which is usually good to help prevent tear out, but it also sucks if it happens because it's more of a pain to clean up, so that's why I provided a list of bits that will save you a lot of time and headache.
Contributor
How perfect and strong does the finished product need to be? With most bandsaw circle cutting jigs you can cut straight thru to the ID you want, then cut the ID and exit back out the starting kerf. Then glue in a piece from the offcut to fill in the kerf.
[OP]
Contributor
This is an option the four pieces will be stacked on top of each other and at least three will be glued and screwed together and the fourth will be screwed to the other three.
Confidence: The feeling you experience before you fully understand the situation
Contributor
To create (4) identical holes I would first make a router jig by using a compass fixture on the router base. Use any size straight bit to do the initial cut; then a follower bit to finish. Then, using this template, I would use the follower bit to make a shallow cut, saber saw the waste to within 1/8", and again use the follower bit to finish.
"Anything seems possible when you don't know what you're doing."
Contributor
I have a "rabbit ear" 12 gauge Rossi coach gun.
It should throw a 12" pattern w/both barrels from about 10 feet away - give or take.
Clean it up with a router & pattern & Bob's your uncle...
Or - just use a router & trammel. No where near as much fun or exciting, but, a lot more neighborly in a suburb.
"Life is what happens to you while you're busy making other plans." - John Lennon
Contributor
Had a chance to try out the method I suggested. I'm making some 5" diameter 1/4" thick cedar rings for some mobiles. Here's some pictures. First two shows right off the bandsaw circle cutting jig, third glue up clamped and the final partly sanded. I made four and some I struggle to find the joint. They are slightly out of round I'm sure but not noticeable to the naked eye.
ring2.jpgring3.jpgring5.jpgring1.jpg
[OP]
Contributor
This is what I ended up doing but I didn't clamp the cut back together. The four rings I made slip over a piece of pipe after they're joined together on top of each other.
Confidence: The feeling you experience before you fully understand the situation
Contributor
One thing to consider when making the thru cut to the ID is to make the cut parallel to the grain. This makes the glue up stronger as it is long grain to long grain and also makes the glue line less noticeable. This wouldn't matter in your case with plywood.
Contributor
I like the look of Greene & Greene breadboard ends. Mounting screws parallel to the top with round and oval plugs hiding the screw heads. No worries about overdriving the screws or making the holes too deep and breaking through the visible surface.
Bill D
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