Non-square routered corners

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Forum topic by Sebas posted 05-09-2016 09:38 PM 866 views 0 times favorited 6 replies Add to Favorites Watch
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5 posts in 1019 days

05-09-2016 09:38 PM

Topic tags/keywords: question router

Hello! First post.

Was wondering if anybody knew what tool to use to router corners that are not 90 degrees.


6 replies so far

View Lee's profile


129 posts in 1149 days

#1 posted 05-09-2016 10:13 PM

Not sure what you mean, a bit with a guide bearing will follow most curves. You might need to attach a pattern with double sided tape to give the bearing something to ride against. I usually make my patterns out of 1/4” hardboard. need to give us more info or a picture. hope this helps

-- Colombia Custom Woodworking

View Sebas's profile


5 posts in 1019 days

#2 posted 05-09-2016 10:31 PM

This kind of thing is what I’m talking about…..

Or another example that has 90 degree routered corners and also non- square corners….

View JBrow's profile


1366 posts in 1191 days

#3 posted 05-11-2016 01:47 AM


I pretty sure I am of no help, but share my thoughts anyway. I am still trying to figure out how the ancients carved those perfectly flat and square inside corners in andesite stones at Puma Punku. Both the question you pose and the Puma Punku riddle are interesting problems. I am interested to know whether this question relates to a project underway or simply an interesting question.

On the prismatoid in the photo, I would think a simple router and round-over bit would handle the vertical intersecting planes (since it is a 4 sided figure), but the top is another matter. Building some form of a router cradle that moves the router in an arc parallel to the round-over arc for the top horizontal plane could work, using a small radius core box bit (though a small diameter straight bit might work). However, I am not sure such a cradle could be constructed to adequately control the router, keeping it from rocking.

Alternatively, for the prismatoid, a CNC machine with x, y, and z programmable movements equipped with a straight bit or core box bit might work.

The shape in the second photo could be partially rounded-over with the same methods as with the top of the prismatoid, but the inside corners where the round-overs intersect would eventually get in the way and preclude a rounding the full length of the inside edges. Of course the machine, whether a router or CNC head, would have to fit inside the cavity of the second shape.

The only other rotary tool method that might work would be to create the round-overs before assembly. Some tapered shims may be needed to hold the router and bit in just the right position. A tilting spindle on a spindle shaper could also work. Using splines to keep the rounded-over joints in alignment during assembly could also be helpful. However, I image this would be difficult to get just right.

If I were confronted with the problem of rounding-over of either of these shapes, I would probably pick up a rasp, a chisel, some scrapers, and sand paper. A small rotary tool like a Dremel could speed the process, but could make fairing the round-over difficult since it can be an aggressive tool for this application. I would round-over edges to witness marks outlining where the round-over dies into the flat surfaces in an effort to keep the round-overs as straight and true as possible.

View jerryminer's profile


944 posts in 1713 days

#4 posted 05-11-2016 05:10 AM

There are bits made to do “non-square” round-overs for solid-surface sink installations, like this one:

bowl bit

For a price, many router bit manufacturers will make a custom bit for you.

But not every round-over has to be cut with a router. Hand tool methods work also, and can be more versatile.

-- Jerry, making sawdust professionally since 1976

View Sebas's profile


5 posts in 1019 days

#5 posted 05-11-2016 11:54 AM

Thanks! I knew there must be a tool. Friends were saying “use sandpaper” and I’m happy there is a better way.

View HokieKen's profile


8229 posts in 1410 days

#6 posted 05-11-2016 04:12 PM

^ That works for your first example, but not the second. No matter how you slice it, you cannot route square internal corners.

-- Kenny, SW VA, Go Hokies!!!

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