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Suggestions wanted, how to make concave body
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10123&t=43059		 Page 1 of 1
Author:  lactose [ Wed Mar 26, 2014 3:15 pm ]
Post subject:  Suggestions wanted, how to make concave body
On a recent test I did with 2x4s, I made a butcher blocked body with each piece cut with a concave curve by the band saw. Then I glued them together, but it was a lot of work getting the pieces leveled out. My finger planes did not have a curved bottom, and scraping and sanding was going way too slow. Should I buy a bent (curved) chisel or round bottom plane, or other idea ? The attached pic shows an idea of hanging a router over the block. Thanks.

Attachment:
wood_concave.png
Author:  Chris Pile [ Wed Mar 26, 2014 4:38 pm ]
Post subject:  Re: Suggestions wanted, how to make concave body
Get yourself a Four-in-hand rasp. It has a curved face, and a flat face - with rasp teeth on one end, and bastard file teeth on the other. Works like a charm.

http://www.leevalley.com/en/images/item ... 901s1b.jpg
Author:  StevenWheeler [ Wed Mar 26, 2014 5:05 pm ]
Post subject:  Re: Suggestions wanted, how to make concave body
Maybe a scorp.

http://www.woodcraft.com/product/2001825/1305/pfeil-swiss-made-scorp.aspx
Author:  B. Howard [ Thu Mar 27, 2014 7:59 am ]
Post subject:  Re: Suggestions wanted, how to make concave body
Gouge out the majority with chisels and refine with rasps, scrapers and sandpaper. An approach like this will also allow you to vary the shape of the contour in all three dimensions to create something that looks nice but also feels comfortable. With a jig as suggested you are stuck creating a straight cylindrical relief and nothing more.
Author:  Quine [ Thu Mar 27, 2014 1:21 pm ]
Post subject:  Re: Suggestions wanted, how to make concave body
The router idea just looks dangerous to me. I'd do it like one of the usual archtop methods.... 1; Drill to specific depths at the edges, middle, center. Then use the holes as a guide for carving. Or 2; use a router and templates to cut terraced depths (like a stair case) then carve away the steps until smooth.
Author:  SJBikesaws [ Fri Mar 28, 2014 10:43 am ]
Post subject:  Re: Suggestions wanted, how to make concave body
Well, if it were me, I would mount it in the mill and cut terraces inward. For rough carving I use an angle grinder with a 40 grit flapper wheel (works great and FAST for alder, decent for maple, but burns mahogany pretty quick). When I hit wood that burns easy, I just take small bites or hit it with an air compressor blow gun while I carve to keep the wheel cool.

You could carve most of it out with a flapper. I am pretty precise with one and even carve necks with one, but I had lots of practice with and angle grinder after a decade of ugly welding. I am also not past pulling out a chainsaw to carve, I guess my methods are pretty unconventional.
Author:  Van Savage [ Fri Mar 28, 2014 11:31 pm ]
Post subject:  Re: Suggestions wanted, how to make concave body
I agree with using the angle grinder.
Author:  cphanna [ Sat Mar 29, 2014 7:26 pm ]
Post subject:  Re: Suggestions wanted, how to make concave body
You've got good suggestions from everyone and a particularly good insight from Brian Howard. If I were doing it, I would go with the gouge, round bottomed plane, scorp, scraper method. The reason I would do this is because I'd rather make shavings than dust and chips. And I would rather hear the hand tool blade against the wood than listen to the motor of a power tool. That's just what I would do. It doesn't mean the other ways aren't valid. They are. And, yes, I use power tools all the time for precision and repeatability, and sometimes getting out working stock. But I much prefer to make shavings in a case like this.
Patrick
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