Making jig for large radius plywood cuts. - Router Forums
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post #1 of 23 (permalink) Old 03-10-2012, 02:54 PM Thread Starter
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Default Making jig for large radius plywood cuts.

A while back I had asked for advice on making curved cuts on 1/8” plywood http://www.routerforums.com/jigs-fix...8-plywood.html and I could not get the router to stay perpendicular with the surface. I finaly gave up and I ended up using my band saw instead. Well I’m not real happy with how it came out using the band saw and I want to do another one only this time with the router.

I recently watched a YouTube video that gave me an idea, Charles Neil Taper Jig - Part 2 - YouTube

Instead of moving the router around the work piece, I’m going to fasten the router to a 4x8 sheet of plywood and rotate the work piece around the router.
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post #2 of 23 (permalink) Old 03-10-2012, 05:09 PM
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If you do that keep in mind that you either have to move the piece into the spinng bit, then lock it down when you reach the pivot point or you have to plunge the router on the centered piece.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #3 of 23 (permalink) Old 03-10-2012, 05:24 PM Thread Starter
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If you do that keep in mind that you either have to move the piece into the spinng bit, then lock it down when you reach the pivot point or you have to plunge the router on the centered piece.
Oh good point.

I believe in the video the guy mentioned drilling a pilot hole first then set the piece on to the router bit before turning it on.

There is one thing that I’m confused about and that is he mentions “pay attention to the rotation of the bit”. Does it mater which way to go if you are cutting a slot in which the bit is cutting on both sides at once?
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post #4 of 23 (permalink) Old 03-10-2012, 07:42 PM
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I've never seen any difference in direction for routing slots, but if you're routing an edge, there is.

There was a excellent version of a radius circle-cutter jig like you're wanting in the Woodsmith Router Workshop book. It was made out of plywood, and all of it 3/4 stock if I remember, but that can be changed. The only plastic they used was the knobs for adjustment.

If you're still intending on using the Rotozip, then you could make a clamp with the plywood to clamp around the round nose of the router, and hold it vertical.

Since that's 1/8" plywood, you might be better using a 1/16" bit. I know Freud makes one. Also, you might have to try a spiral bit, I'm not sure due to the thinness of the plywood.
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post #5 of 23 (permalink) Old 03-10-2012, 07:51 PM Thread Starter
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I've never seen any difference in direction for routing slots, but if you're routing an edge, there is.

There was a excellent version of a radius circle-cutter jig like you're wanting in the Woodsmith Router Workshop book. It was made out of plywood, and all of it 3/4 stock if I remember, but that can be changed. The only plastic they used was the knobs for adjustment.

If you're still intending on using the Rotozip, then you could make a clamp with the plywood to clamp around the round nose of the router, and hold it vertical.

Since that's 1/8" plywood, you might be better using a 1/16" bit. I know Freud makes one. Also, you might have to try a spiral bit, I'm not sure due to the thinness of the plywood.
I'm not going to use the RotoZip. I'm planing on using my Porter-Cable Fixed-Base Router and I'm also planing on cutting 3 at a time stacked on top of each other.

I would like to see that Woodsmith Router radius circle-cutter jig
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post #6 of 23 (permalink) Old 03-10-2012, 08:30 PM
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Hi John

Here's some of the WoodSmith items I did not dig to deep into them but you may want to check them out ,you may find what you need.

Free Woodworking Plans, Downloads and Videos - Woodsmith Shop

http://www.woodsmithshop.com/downloa...-circlejig.pdf
Router Circle Cutting Jig for Woodworking
Woodsmith Magazine Index

Shop Jig Plans - Build Table Saw Jigs, Router Jigs, Boxjoint Jig
Workshop Projects

http://www.routerforums.com/general-...ns-needed.html

http://download.plansnow.com/plansno...circle-jig.pdf

==========
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Originally Posted by JohnnyB60 View Post
I'm not going to use the RotoZip. I'm planing on using my Porter-Cable Fixed-Base Router and I'm also planing on cutting 3 at a time stacked on top of each other.

I would like to see that Woodsmith Router radius circle-cutter jig



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post #7 of 23 (permalink) Old 03-10-2012, 10:07 PM
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I think you can still do a google search for the book in mention, and find a place to download a copy of it.

Do a search for: Woodsmith Router Workshop.pdf

The file should be about 11 megs in size.
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post #8 of 23 (permalink) Old 03-10-2012, 11:12 PM
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[QUOTE=JohnnyB60;274776]Oh good point.

I believe in the video the guy mentioned drilling a pilot hole first then set the piece on to the router bit before turning it on.

There is one thing that I’m confused about and that is he mentions “pay attention to the rotation of the bit”. Does it mater which way to go if you are cutting a slot in which the bit is cutting on both sides at once?[/QUOTE

As a router bit turns, you should be pushing your piece into the cutter face of the bit. If you go the other way, the bit will "climb cut" and your piece will try to self feed into the bit which can cause very bad things to happen. If you are profiling an edge onto a board, for an example, and the router is trying to pull you along, you are going the wrong way.
Where both edges are cutting the forces should theoretically balance out but there might be a little bit of a problem at the very end of the cut as the outer piece is ready to part off. I would still feed towards the cutter face just to be sure.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #9 of 23 (permalink) Old 03-10-2012, 11:48 PM Thread Starter
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Originally Posted by Cherryville Chuck View Post
As a router bit turns, you should be pushing your piece into the cutter face of the bit. If you go the other way, the bit will "climb cut" and your piece will try to self feed into the bit which can cause very bad things to happen. If you are profiling an edge onto a board, for an example, and the router is trying to pull you along, you are going the wrong way.
Where both edges are cutting the forces should theoretically balance out but there might be a little bit of a problem at the very end of the cut as the outer piece is ready to part off. I would still feed towards the cutter face just to be sure.
See this is what I’m confused about because there is only one pilot hole and there is only one way to go. Even if the pilot hole is on the other end of the radius there is still only one way to go.
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post #10 of 23 (permalink) Old 03-11-2012, 12:06 AM
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Quote:
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A while back I had asked for advice on making curved cuts on 1/8” plywood http://www.routerforums.com/jigs-fix...8-plywood.html and I could not get the router to stay perpendicular with the surface. I finaly gave up and I ended up using my band saw instead. Well I’m not real happy with how it came out using the band saw and I want to do another one only this time with the router.

I recently watched a YouTube video that gave me an idea, Charles Neil Taper Jig - Part 2 - YouTube

Instead of moving the router around the work piece, I’m going to fasten the router to a 4x8 sheet of plywood and rotate the work piece around the router.
Making a trammel arm for your router is easy with some scrap material. I used 1/4" for this trammel & mounted a PC690 router. I make all markings for measurements before drilling any holes. I like mark one side of the jig for inside radius & the other side for outside radius. I sue a double head nail or finish nail for a pivot point. I like to use a 1/2" straight bit for easy measurements for different radius's. I used this same trammel for a 60" round table top. For thick material just increase the depth on each pass. For 3/4" ply such as in pictures I did 3 passes. Cost can be as cheap as the type of scrap you have lying around.
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James
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Have a nice & safe day!

Last edited by jlord; 03-11-2012 at 12:09 AM.
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