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Shaping elliptical, curved chair legs

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Shaping elliptical, curved chair legs

Edited #1

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I am building dining room chairs (and a dining room table), and the chairs will be similar to the one below. It has been fun designing and dimensioning :)
2.jpg
The legs are both curved and have an elliptical profile. Because of this, they cannot be turned on a lathe. I have created a template, partly for marking out and partly a potential pattern for a router table.
Here is the "however" ... the wood is Rock Maple (or Hard Maple) and I have never routed this with pattern bits. I have read that it is not a good choice of wood for this method (tending to blow out and blow up at the suggestion of cutting into the grain).
When it comes to shaping, my preference is to use hand tools ... spokeshaves, etc. I have build a similar chair completely with hand tools in the past, an exact copy of Hans Wegner's "The Chair", even copying the mortice and tenon joinery with hand tools. This is a piece of furniture built in the factory with lathe copiers.
Mine on the left, original on the right ...
823x567
426x688
When it comes to the dining chair, you can see that I like the style :)
So ... shape the legs with spokeshaves, or what router bit and method can be suggested? 
Regards from Perth
Derek

Re: Shaping elliptical, curved chair legs

#2

Ellis Walentine

Ye gods, Derek. Could you have found a more complicated challenge?

Couple thoughts:  I can't confirm what you've heard about rock maple. The biggest obstacle to routing it is the fact that it tends to burn so you need to keep the router moving. Spokeshaving won't be too easy either. They call it "rock" maple for a reason.

As for the elliptical profile, I don't know how faithful you plan to be with achieving a reasonably elliptical section at all or most points on the legs. The fact that they are not of uniform width will further complicate the shaping. I'd probably use a straight pattern bit in one dimension to produce the (side elevation) shape, then mortise for the seat, then get a custom half-elliptical rounding bit matching the largest dimension of the shape (if this makes any sense), then smooth out any anomalies with your Dynabrade. If you want to be more precise than this, I'd suggest finding someone with a CNC machine; although, how you'd program it, I have no idea -- use a 3D scanner on on your prototype probably. 

In the old days, I had a couple pneumatic sanders -- one a two-ended two-bagger (one 3" and one 6" diameter) and a hand-held unit. These could be used with varied air pressure and grits to get just the bite needed for finish shaping on a project like this, although it is definitely in the workmanship-of-risk category. There will still be plenty of rasping and filing to clean up all the joinery. 

The end result will be worth the effort. I need to make six or eight chairs of a similar shape and size to go with the trestle table I built last summer, but I don't have the temerity (or the shop) anymore to pull it off. Maybe you could just make a few extras for me while you're at it.

Cheers,
Ellis

Re: Shaping elliptical, curved chair legs

#3

Derek,  may I suggest you start the process of shaping the legs with a Drawknife?  It would move a fair amount of wood to start and let you then proceed to the spoke shave as a finishing tool..P

Re: Shaping elliptical, curved chair legs

#4

Make a series of templates out of good multi-ply for each part of the leg.  Three or four should do it.  Shape to the templates and blend in-between with whatever turns you on.  

The legs don't have to be perfect.  The eye will impute uniformity.

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