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Forum topic by ravensrock posted 02-25-2017 06:40 PM 726 views 0 times favorited 21 replies Add to Favorites Watch
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ravensrock

465 posts in 1478 days


02-25-2017 06:40 PM

Topic tags/keywords: question

I’m making a matching arm rest for a metal porch swing. There is a dado along its length where it screws into the arm from the swing. Very simple if it wasn’t for the curve. The base of my compact router is too broad to follow the curve. Even the shoulder plane I have presents the same problem. Any suggestions?

-- Dave, York, PA, Wildside Woodworking


21 replies so far

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jbay

1856 posts in 735 days


#1 posted 02-25-2017 06:45 PM

It looks like the bottom is flat?
Turn it on it’s side and use a rabbiting bit with the proper size bearing to give you the desired depth.
Start at the bottom and move it up until you get the width you need.

-- If anyone would like to see my Portfolio, PM me and I would be glad to send you the link.

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Rich

1978 posts in 425 days


#2 posted 02-25-2017 07:33 PM

You don’t mention having a band saw as an option, but it’s made for that sort of cut. You would saw the long side to its shape, tape the pieces back on and then make the cuts on the side.

-- No matter how much you push the envelope, it'll still be stationery.

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ravensrock

465 posts in 1478 days


#3 posted 02-25-2017 08:04 PM

jbay- I can see how that could work. Might give that a try.

Rich- I do have a bandsaw. I already have the arm rest cut to shape. I’m wondering about the dado. Is that what you are referring to?

-- Dave, York, PA, Wildside Woodworking

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Rich

1978 posts in 425 days


#4 posted 02-25-2017 08:08 PM

I apologize. I didn’t read your post carefully enough. The rabbeting bit is a great idea, but to get that depth, it looks to me like you might need a bit extension.

-- No matter how much you push the envelope, it'll still be stationery.

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ravensrock

465 posts in 1478 days


#5 posted 02-25-2017 08:10 PM

I think you’re right. And I don’t think I have one of those. I’ll have to check.

-- Dave, York, PA, Wildside Woodworking

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Loren

9623 posts in 3483 days


#6 posted 02-25-2017 09:24 PM

I would be tempted to cheat by cutting some
thin strips of material and gluing it to the
bottom. It only looks to be 1/8” deep and
material that thick bends to mild curves
easily.

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Dave G

328 posts in 1884 days


#7 posted 02-25-2017 11:05 PM

In the time it took to talk this through we could have chiseled it by hand.

-- Dave, New England - “We are made to persist. that's how we find out who we are.” ― Tobias Wolff

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chrisstef

17024 posts in 2842 days


#8 posted 02-25-2017 11:13 PM

A router plane would get ya there. I guess the other option would be a router sled riding on a jig with the same radius as the piece.

IMO, Lorens got the ticket.

-- Its not a crack, its a casting imperfection.

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builtinbkyn

1921 posts in 776 days


#9 posted 02-25-2017 11:33 PM

As jbay said above, a table mounted router with a rabbeting bit and bearing, is the way to go.

-- Bill, Yo!......in Brooklyn & Steel City :)

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ravensrock

465 posts in 1478 days


#10 posted 02-25-2017 11:55 PM

Thanks for the suggestions everyone. I just got back from getting the right bearing for my rabbeting bit. I’ll give it a try tomorrow.

Loren- I like that idea. It is only 1/8” so if the rabbeting bit looks like it won’t work I’m going to give this a try. I would just have to take the eighth off the other face to keep the dimensions the same.

-- Dave, York, PA, Wildside Woodworking

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EricTwice

228 posts in 369 days


#11 posted 02-26-2017 12:06 AM

Why not try a router with a flat bottom mortising bit. You would have to make a curved sole plate and a fence for it. The sole plate should be roughly parabolic and the bit should rise from the center or high point. The top of the plate can be flat but not much wider than the diameter of the bit.

I think I would start by making a thick sole plate that is square and flat and then run the bit through it giving you a zero clearance plate and marking the cutting area. Take the plate off and clip the front and back on the band saw up to the hole where the bit comes through. Now the curved piece will run on the top and not bind on the front and back edges. Sand it smooth and countersink the attachment screws. The fence is just a flat scrap that fits your curved sole and can be clamped or screwed in place.

I think a router table would be too big and cumbersome to work. I would clamp the router in my shoulder vise, lacking that I’d use clamps to keep it from moving on the bench. I would run the wood across the router rather than the other way round.

-- nice recovery, They should pay extra for that mistake, Eric E.

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Tony_S

766 posts in 2919 days


#12 posted 02-26-2017 01:33 AM


Why not try a router with a flat bottom mortising bit. You would have to make a curved sole plate and a fence for it. The sole plate should be roughly parabolic and the bit should rise from the center or high point. The top of the plate can be flat but not much wider than the diameter of the bit. I think I would start by making a thick sole plate that is square and flat and then run the bit through it giving you a zero clearance plate and marking the cutting area. Take the plate off and clip the front and back on the band saw up to the hole where the bit comes through. Now the curved piece will run on the top and not bind on the front and back edges. Sand it smooth and countersink the attachment screws. The fence is just a flat scrap that fits your curved sole and can be clamped or screwed in place.

I think a router table would be too big and cumbersome to work. I would clamp the router in my shoulder vise, lacking that I d use clamps to keep it from moving on the bench. I would run the wood across the router rather than the other way round.

- EricTwice

This works to some degree but will leave a radial surface on a concave radius cut. Multiple passes (side by side)will leave a scalloped surface.
It works well if the surface is convex, as long as the radius on the router base matches the convex surface and the bit is perfectly centered. It typically won’t leave as clean a surface as the bit normally would when used in a normal manner.

OP
In this instance, a couple of passes with a rabbet bit, and it’s done.
One thing I would have done in this particular instance, is cut the the convex section first and clean it up, then cut the dado with the rabbet bit…...then finish the rest of the cuts.
This way, you’d have a larger, more stable surface for the router base or table.
It’ll still work though this way though.

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

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EricTwice

228 posts in 369 days


#13 posted 02-26-2017 10:00 AM

This works to some degree but will leave a radial surface on a concave radius cut. Multiple passes (side by side)will leave a scalloped surface.
It works well if the surface is convex, as long as the radius on the router base matches the convex surface and the bit is perfectly centered. It typically won t leave as clean a surface as the bit normally would when used in a normal manner.

- Tony_S

This is true. However, given a 3/4 bit and the shallow curve of the piece the scalloping would be minimal. Probably no worse than the lines left in the original milling, and could easily be cleaned up with sandpaper and a block if they are problematic. given where they are, you would probably never see them if you ignored them.

Unless your rebate plane has a curved sole, it is going to be problematic.

-- nice recovery, They should pay extra for that mistake, Eric E.

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Tony_S

766 posts in 2919 days


#14 posted 02-26-2017 11:24 AM


This is true. However, given a 3/4 bit and the shallow curve of the piece the scalloping would be minimal. Probably no worse than the lines left in the original milling, and could easily be cleaned up with sandpaper and a block if they are problematic. given where they are, you would probably never see them if you ignored them.
Unless your rebate plane has a curved sole, it is going to be problematic.
- EricTwice

I agree Eric. In this instance it wouldn’t really make any difference at all. More of a mention for someone who might want to try it on an exposed surface.
No idea on the rebate plane, never used one before, but I would think your correct, straight and curved don’t mix. I’d be surprised if it worked at all? A compass plane of some sort for sure.

My whole point being, not that you’re wrong…Your suggestion would work, without a doubt, I’ve done it.
But using a rabbet bit is much more efficient. I would be done 50 of them with a rabbet bit (or shaper)before your even done making the router base.
I’ve done it hundreds and hundreds of times, in both manners.

-- It is the mark of an educated mind to be able to entertain a thought without accepting it. Aristotle

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Ron Aylor

1775 posts in 483 days


#15 posted 02-26-2017 11:40 AM

I would just use a paring chisel and take my time …

-- Ron in Lilburn, Georgia.  Knowing how to use a tool is more important than the tool in and of itself.

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