How would you route this radius??

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Hi guys, as I cannot ww I spend my time trying to think about new projects and have them ready so that when I'm recovered I have plenty of them to make. LOL.

This is the seat of a small stool I'm designing and I have a doubt.

Is it possible to route the corners of piece "A" to obtain the rounded edges and corners of piece "B" using a radius router bit with a bearing? How? Being it curved the only way I think it coud work would be gluing two rods on the table router to make it glide in a circular way always at the same height (see sketch) but how to control it at the end of the piece? And what height should those rod have if this is the way?

FWW tab.jpgfmm 2.jpg

Any help will be appreciated.
 
Toni,

I would make a sled with the radius of the back of your piece so the piece would be supported throughout the routing process. It could be 1/4" thick at the center of the bit, then match the height of the ends of the piece. Raise the bit 1/4" to match the offset of the sled.
 
Easy to overthink this one. This is the job for the router in a table. And a hole in the table top very close to the diameter of the cutter. You want support for your workpiece as close to the cutting action as possible. I think there is something in my book that deals with doing it yourself router bases. The router table top is actually a router base - just bigger!

Before you rout anything, draw a pencil line in the middle of the edge which will represent the path of the router bearing.
Now envision the bearing path at always remaining perpendicular to the vertical center of the bit. For the bottom radius, run the piece with the face of the wood on the table. For the top, you will need to run it on edge. Do the bottom first so you get a feel for the feed actuan.

Do a dry run (router off) and 'rock' the workpiece along to keep the bearing on the bearing path line. You will be able to see the bearing folow the path you drew on the edge. Do another dry run with the piece on edge. You will no longer be able to see your pencil line, but at this point it is not necessary. If you do multiple pieces, you will likely only need your pencil line on the first piece, as it is there to teach you what your movement need to be to make the cut successfully and safely.

Be mindful of the rotation of the cutter and make sure you are feeding the workpiece INTO the cutting edge of the bit. If the first part of the cutting edge that hits the wood is the back of the edge, things will get out of control very, very quickly. True of all routing actions. Called climb cutting. Can be done safely, but this is not the place for it.

Now that your hands and your brain experienced how the cut can go, turn on the router and go for it. You will be amazed at how easy it actual can be.

The beauty of a router bit with a bearing to guide it is that you cannot removed too much wood. If the path of feeding the wood into the bit is not consistent, you will have 'bumps' on the routed surface. Just run it again. You can't remove too much wood.

The keys here are the diameter of the base hole, the direction of the feed path, and visualizing the action beforehand.
 
Fences and bearings together on a router table are counterproductive and can lead to unsafe procedures. Called the wedge maneuver powered by 23,000 RPM! Flak jacket, hardhat, drop to the floor and yell 'Incoming'!
 
Did a curved piece similar to your seat the other day. As Carol says try a dry run (router off). It will help you to visualize the cutting action and hand movement. Just be aware off tear out on your short ends (I'm assuming the grain runs the long side). Best to do short sides first before the long sides.
 
Thanks a lot to all of you. Specially to Carol, after your thorough explanation it feels much easier that I thought, specially if as you mention one cannot remove too much wood which was one of my fears, now I understand it, the bearing limits the invard cut and the table top limits the downward one, so need for special supports or whatsoever, just mind where my hands are as usual.
 
Maybe I am not following completely, but it seems like everyone produced a solution for the convex side, but nobody addressed the concave side, and the picture suggests that both sides need to be rounded. It seems like the solution would be to have the edge against the table, and perhaps a block of wood held behind the workpiece to keep it vertical.

Of course, with Toni's carving skills, the faster solution may be to just grab a pocket knife and whittle away.
 
with Toni's carving skills, the faster solution may be to just grab a pocket knife and whittle away.

I had a similar thought. Some things a just not intended to be perfect. Instead of the router, hand holding onto a sanding belt might produce the effect sought with more safety and less fuss.
 
Well, if I were tackling this I would first rough out the round over by hand. I would only do this on 1/2 of each face, the half that the router wants to tear out. A spoke shave and/or carving tools will do the trick. This roughing out will reduce the amount of material the "against the grain router cut" will have to make, reducing the chances of splintering out. AND THIS PIECE WILL BE VERY PRONE TO CHUNKING/SPLINTERING OUT!

After that, a jig with hold downs is the direction I personally would take in my shop. Something to add a bit of stability and security while running it on the router table. But with a compound curve that's probably not possible.

I have run curved parts on a router table against the grain with virtually no tear-out, but that was with a spiral straight cutter. I think this piece is a bit more likely to have massive chunks splinter away. Tricky. I can't wait to learn of what works!

Do you have a spare/extra? Whenever I make a part that has a process that concerns me I make an extra or two while I am making the "keepers". Not really helpful now, but this method has really saved me a lot of headache in the past.

-Hutch
 
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Even though I have several routers, and a Woodpeckers router table, I probably use a spokeshave for this job. It'd likely take about ten minutes to round over all sides of it. Minimal sanding, and it's done.
 
Maybe I am not following completely, but it seems like everyone produced a solution for the convex side, but nobody addressed the concave side, and the picture suggests that both sides need to be rounded. It seems like the solution would be to have the edge against the table, and perhaps a block of wood held behind the workpiece to keep it vertical...

Carol addressed that with roughly the same advice:

...For the bottom radius, run the piece with the face of the wood on the table. For the top, you will need to run it on edge...

Carol, is there any reason both the convex and concave sides couldn't be shaped with the workpiece on its edge? Of course, it seems to me the ends will be a bit trickier any way they get done.
 
Yes, they can both be run on edge. I suggested the other to help Toni build confidence in 'rocking' the piece past the cutter.

And yes, running the short ends first will help prevent tearout. The best thing for that though is a very sharp bit. There is a technique to handle short ends but it is hard to explain and I have no one to help me make a video to show it.

In retrospect, and this is for Toni, run the concave side first on edge. Then run the convex side. Opposite of what I said above. The reason is you will have more support for the concave cut that way. Wish Toni was closer, so I could walk him through this. If I ever get a shop again, Maybe I should make a series of YouTubes demonstrating techniques.
 
To Carol, Charlie, and the rest, thanks a lot for your suggestions, getting tear out is another of my fears so I will proceed as you suggest. I will post the process and the final results once my arm is healed enough to start ww which I am missing a lot.
Now I think everything is clear. Run concave side on edge and short ends first then run convex side either on edge or flat face, trying on a dummy piece first. Although if it doesn't feel safe I will take Jim's suggestion and use a spokeshave eventually.
 
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