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How to route a shallow recess?

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Forum topic by RussInMichigan posted 10-03-2011 02:22 PM 3324 views 0 times favorited 9 replies Add to Favorites Watch
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RussInMichigan

478 posts in 1436 days


10-03-2011 02:22 PM

Topic tags/keywords: routing shallow recesses question

Question.

I want to make a round mirror from 5/8” stock. I’m thinking that I will put the mirror itself into a round recess that is 3/8” deep. I want to round over the edges of the recess with a 3/16” radius. However, I realize that I have never routed a recess like this one that was too shallow to use the bearing on the router. So, how do I round over the edges of my shallow mirror recess? I’m planning to make a few of these so I’d like to avoid shaping those edges by hand. Any insights would be appreciated.


9 replies so far

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richgreer

4524 posts in 1730 days


#1 posted 10-03-2011 03:08 PM

This is an interesting challenge. There may be better approaches than I suggest here but these are the only 2 ideas I came up with.

(1) Glue up – Cut your recess extra deep with a straight bit. To get the desired shape you can use a template and a bushing or what I call an external template that you run the base of the router against. Then, with the extra deep recess, use a conventional round-over bit with a guide bearing. Then remove the bottom of the board by resawing or with a thickness planner. Then glue a new bottom on.

(2) Remove guide bearing from bit – I would only do this if you were going to use this bit multiple times. In addition to unscrewing the guide bearing you would have to grind off the bottom of the bit (this is not a reversible procedure). You would have to use an external template because you could not use a bushing with this bit.

Someone else probably has a better idea.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

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RussInMichigan

478 posts in 1436 days


#2 posted 10-03-2011 06:46 PM

Thanks much, Rich. These are both useful ideas.

I’d really like to somehow get your second idea to work since I want to hog out the recess using a template and a bushing with a flat bit. It would be really nice if I could use the same circular template and just change bits and bushings so I don’t have to completely change the setup for every new workpiece.

Thanks again for the help. I’m going to tinker with option two a bit and see if I can get it to work. If I can make it work, I’ll post the projects for you to see.

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Richard

906 posts in 1346 days


#3 posted 10-03-2011 09:29 PM

bentlyj , if I read this correctly he wants to round over the the inside edge of the recess for the mirror and I don’t think the jig you show would do that. But it looks great for doing the outside edge of the coasters I plan on making.

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RussInMichigan

478 posts in 1436 days


#4 posted 10-03-2011 09:29 PM

Thanks, bentlyj,
I can see how that might work for the exterior of a circular object but I need to round over the edge of a 3/8” deep interior recess. The project is a mirror, a 5” mirror in a 3/8” deep recess in a quite non-circular handle.

I wanted to bounce this off my fellow lumberjocks to see if I was just missing out on a standard technique.

Thanks again,

Russ

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SPHinTampa

548 posts in 2341 days


#5 posted 10-03-2011 09:48 PM

Could you use a template, guide bushing and a sign makers bit?

Put template around inside of recess, use large bushing (larger than outer radius of sign makers bit, mount sign makers bit and use outside edge of bit. Only works if recess is wider than bit.

-- Shawn, I ask in order to learn

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richgreer

4524 posts in 1730 days


#6 posted 10-04-2011 12:56 AM

FWIW – After thinking further, I think my approach number 2 above would work with a bushing if you had a shallow bushing and a thick template. However, you would probably not be able to plunge into the work with the plunge feature of your router.

Personally, I like using external templates that I run the base of my router against if, and only if, I have a router with a base that has a significant round portion. Some routers have big flat portions on their base and/or bumps where the plunge mechanism connects. It’s important to keep the bit the exact right distance from the edge of the template.

-- Rich, Cedar Rapids, IA - I'm a woodworker. I don't create beauty, I reveal it.

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RussInMichigan

478 posts in 1436 days


#7 posted 10-04-2011 06:12 AM

Rich,
I still haven’t found what I conceive of as an elegant and straightforward solution. I’m still toying with some combination of templates and bushings and removed router bearings. I’ve been wondering if I can use a bushing that will maintain the same distance from template to edge of cutting surface as I would get with the bit/bushing combination I use to clear the recess. If so I could just swap out the bit/bushing pair and use the same template without moving the workpiece.

I’d like to find something that’s not too cumbersome. I prefer reducing the chance for error to a minimum.

Thanks again. I like having someone brainstorm these things with me.

View rance's profile

rance

4132 posts in 1816 days


#8 posted 10-04-2011 06:56 AM

Actually, I would go with Bently’s method. Yes, as he drew it, it would be for the outside, but there is nothing to keep you from making a convex rather than the concave he drew and use that method. You’d end up with a 1/4 of the circle with the bit on the arc of the circle. I can draw a pic if you need. Kudos to Bently on this.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

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RussInMichigan

478 posts in 1436 days


#9 posted 10-04-2011 01:53 PM

Thanks Rance.

I think you’re right. I think all of you who responded had a bit of the solution in your mind’s eye. Rather than an outside template I could make an inside one. Then I could run the workpiece around it. I could align the narrowest part of the cutting edge with the outside of the template.

Still I was hoping to find a solution that would let me cut the recess and route the roundover without having to move the workpiece, or more to the point, without moving the edge to be routed away from the template.

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