Monday, February 25, 2008

More Brace Carving

Last night I spent about 90 minutes carving the top braces, I am about 90% done with the carving. I just need to work the ends of the braces so they fit in the kerfing slots (which haven't been made yet) and then some sanding. Once it gets glued to the sides, it may be necessary to remove more material depending on how it responds to mechanical excitation (tapping).
The first chisel I bought was a 10mm (3/8"), this seemed to me the appropriate size. But acting on the advice of a fellow luthier, I later bought a 16mm (5/8"). After using them for the night, the 16mm definitely has the best feel. A larger chisel seems counter-intuitive to me, but gave me the best control. I don't think it has anything to do with physical size, but rather due to its larger mass/inertia.

Monday, February 18, 2008

Brace Carving

When I first began carving the braces I used the sanding dish as a base... until I made a few gouges in my sanding dish - *doh!*. I realized then that I needed a workboard: 1-1/2" thick piece of plywood cut out in the shape of the guitar with a cork shim around the edge to account for the slight radius on the top. So I made one, wasn't too hard. It has a 2x2 bolted onto the bottom down the middle so a vice can grip it. The workboard has threaded inserts in it so the 2x2 can be removed if desired. Next, I realized that my Harbor Freight chisels weren't going to work. So I ordered better ones, see previous post.
Finally, I needed a really small plane to help work the braces into a more triangular/rounded shape. The small kunz plane (3-5/16" sole) I have is just too big for this. I found an Ibex #2 flat sole (30mm) finger plane at Woodcraft on closeout, perfect. Couple this with my $10 gift card and it only cost me $27. This plane and the 3 chisels cost me $105 total, *sigh*. Oh well, they'll last a lifetime.
This picture shows the workboard being supported by the Versa Vice at an angle. Although this feels a bit high, not sure if I can use it this way. Alternatively I can clamp the workboard to the bench directly, but then it is more difficult to rotate it around compared to being in the Versa Vice.
Also of note, as you can see I covered the exposed areas of the underside of the top with heavy white paper to "protect" it from chisel error. Obviously a sharp chisel will slice through this if enough force is applied, but it does help.

Chisels

Initially when I began carving the top/back braces, I had a cheap set of chisels from Harbor Freight. Six chisels (1/4 - 1-1/2") for $4, what could I lose (besides the $4). I soon learned that besides the poor quality machining that was used to manufacture these third rate chisels, I just couldn't get them to hold an edge very long. So I checked their hardness: 48-50 Rockwell C... cheap carbon steel. Good chisels have a hardness of 58-62 Rc. So I spent some money and bought three Hirsch Firmer chisels (6, 10, 16mm which is close to 1/4, 3/8, 5/8") from Lee Valley for about $20 apiece plus shipping. Hirsch and Two Cherries are made in the same factory in Germany, and are essentially the same chisel. I have read multiple articles comparing various brands. They all agree that Hirsch/Two Cherries are the toughest (which means holds an edge longer) chisel available with the exception of the much more expensive Japanese chisels: iyori, blue and white steel. To achieve this added toughness, their hardness is higher (62-67 Rc) and thus becomes more brittle. A chisel as such may have it's place, for for what I do the Hirsch is perfect and reasonably priced. Barr and Crown also scored well. Crown is similarly priced at $15-20 each, but Barr generally cost a $70-80 each!

Saturday, February 16, 2008

Versa Vice

My brother-in-law Jerry gave me a Versa Vice a few months back, he even re-painted it for me! This is the original Versa Vice, not the current Parrot vice sold today. The main difference as I can see is that the original has taller jaws, whereas the Parrot vice has shorter, wider jaws. Anyway, I've always been hesitant to drill mounting holes for it in my melamine top. So I built a 6" extension using roller ball bearing drawer slides. That way when I'm not using it I can simply remove it from the workbench to have a clean top to work on.
This vice is so flexible compared to standard vices. It can rotate and pivot to just about any orientation... which will come in handy for shaping the braces on the top.

UPDATE: It is interesting, Brownells.com sells what looks like the Parrot vice (only painted green) for a LOT more money, they call it the MULTI-VICE. I can't figure out the difference. Brownells is a gunsmithing store.