Convex / concave surface router jig

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Forum topic by Viktor posted 03-03-2013 09:19 AM 96606 views 19 times favorited 7 replies Add to Favorites Watch
View Viktor's profile


476 posts in 4749 days

03-03-2013 09:19 AM

Topic tags/keywords: jig router shaping

This is just a variation of a very common router surfacing jig, except instead of flat surface it creates convex or concave one.

The bridge that supports the router has curved beams (R= 194 cm) which I cut using oversized circle cutting jig. The frame is made from Bosch 45mm T-slot aluminum extrusions and brackets that are very handy for building various temporary contraptions.
The piece in the picture is headboard (50×109 cm) for twin bed. It was glued from two pieces of sapele each 25 cm wide. I glued them at 7 degree angle to best conform to the target curvature. It turned out to be very easy to do with track saw. Set the angle to 3.5 degree and trim the edge matching grain pattern of adjacent boards. After this I proceeded straight to glueup. The edges were so straight and smooth that I can barely find the seam after it’s all done.
I attached the work piece to the wooden beams of the frame with small nails. The beams supporting the work piece were bolted to aluminum brackets through elongated slots that allow accurate vertical adjustments of each corner. After surfacing on both sides 20 mm thick board was reduced to 17 mm. If you increase the number of segments thickness loss can be further reduced.

For concave side just flip the router jig (I reattached the router base with screws).

I found it is much easier to make passes along aluminum extrusions than working across. The bridge has to be twice as long as the width of the work piece (my was too short, so I attached the router off center and worked from the opposite sides).

I used 35 mm diameter surfacing bit. It works fine on the convex surface. On the concave side the router has to be tilted like so:

When tilted, flat bottom bit produces shallow elliptical grove rather than rectangular one. In this case passes must be made along the work piece, not across, to have seamless transition.

Final product:

If the rail was circular (a large ring around work piece), one could produce spherical (bowl/dome) shape.

7 replies so far

View watermark's profile


484 posts in 3273 days

#1 posted 03-03-2013 06:43 PM

Great ingenuity there!!

-- "He who has no dog, hunts with a cat" Portuguese proverb

View Bruce Taylor's profile

Bruce Taylor

21 posts in 3269 days

#2 posted 03-03-2013 06:59 PM

Boy, do I have a lot to learn!

-- Captain Bruce, Washington State

View Viktor's profile


476 posts in 4749 days

#3 posted 03-03-2013 08:08 PM

P.S. Here is the bed for which the curved board was made

View a1Jim's profile


118308 posts in 4908 days

#4 posted 03-03-2013 08:29 PM

Good thinking. Well done.


View RogerInColorado's profile


321 posts in 3285 days

#5 posted 03-04-2013 12:24 AM

Very cool and very creative. I can see lots of applications for that.

View gfadvm's profile


14940 posts in 4021 days

#6 posted 03-04-2013 02:27 AM

Very innovative jig! I always wondered how to route concave/convex profiles. Thanks.

-- " I'll try to be nicer, if you'll try to be smarter" gfadvm

View Bernie's profile


422 posts in 4168 days

#7 posted 03-04-2013 02:38 AM

Beautiful simple jig – love it. Thanks for sharing. I’m sure I’ll be using it in the future.

-- Bernie: It never gets hot or cold in New Hampshire, just seasonal!

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