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Special Edition Build Off: The Thumfinizenvette

#182
I'm just gonna leave this here...

IMG_20210228_121931.jpg
 
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#184
Yes! I got a few steps in then had to stop for the day. I think they're going to turn out OK.

I glued up the thick base and a contrasting top, let it cure, then made little perpendicular saw cuts to a centerline, and glued in slivers of rosewood for indicator lines. Then put them through the drum sander to clean them up. Next I drilled a 9/16" countersink to sit over the pot's nut. Then put a 1" hole saw in the drill press and drilled down the center until the hole cutter just barely kissed the surface - this gave me a 1/4" hole for the pot shafts centered on the saw mark.

IMG_20210228_150527.jpg


After that, I took them to the bandsaw and cut a slice off the edge such that it just barely kissed the saw cuts - this is important as it gives a path for the hole saw to eject wood chips, otherwise it just loads up and burns. Then I drilled little holes in from the side for set screws, and finally put them back on the drill press with the hole saw again, but with the pilot bit removed. I used the hole saw to cut until there was 1/16" of wood left holding the plugs in the stock, then I put the stock back through the drum sander which sanded off that 1/16" and released the knobs.

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Just have to give them a quick sanding to clean up the burn marks and round off the tops. Then I'll soak the rosewood sliver in thin CA to make sure it's stable, give them a few coats of finish, and they're done.

The maple knobs with bubinga tops are going on this bass. The other knobs are cherry with maple tops, they are going on two electric ukes I have in progress right now.

This might just be the last thing I need to change on this bass. It's really just spectatular otherwise.
 
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#188
dwizum said:
I buffed out the finish with some wax tonight and mounted the pickups, tuners, and bridge.

Just to confuse you simple minded right handed people, I put the pickups in backwards.

View attachment 3806605

Actually I did it for a good reason, because when they're this way around the wires exit the pickups right at the cavity opening. If I mounted them the "right" way around, the wires would have to travel along under the pickups to get over to the cavity.

On a different subject, I had a question in PM asking for more details on the radius routing jig. I want to say again that I basically ripped this idea off others who did it, but I'm happy to share my version.

I use it with my normal "rails" from my router planing setup. They're built up from 1/2" mdf cut into strips. There's a flat strip on the bottom to provide a base, and vertical strip that's 3" tall (I think?) that the router sled rides on. There are a series of shorter strips on the inside of the vertical, both to act as reinforcement and to act as "steps" to put thinner workpieces on top of.

View attachment 3806611

The rails are free standing, they're not attached to the table or each other. When I'm using this jig, I put a long bar clamp on each end of the rails to basically turn them into a giant clamp and clamp the workpiece in between them. I clamped a hunk of cherry between the rails here for demonstration purposes:

View attachment 3806614

That's shown with the router in my normal planing sled. The idea is that you move the sled back and forth and side to side and the blade is held at a constant height over the workbench, so it cuts the workpiece flat and true. I slide the router from left to right along the far edge of the workpiece, then move it towards the front of the bench an inch (the bit is 1 1/4") and slide it right to left. Then forward an inch, left to right and repeat as needed.

The radius jig works on the exact same principle, except the curved rails on the radius sled cause the router to move along a curve. So, basically, as you go left to right, you're cutting along a straight path. And every time you "index" a step forward for the next path, you follow a curve. The end result is that the workpiece is carved into a shape that resembles a slice of a giant cylinder.

I showed the curved sled earlier, here it is again:

View attachment 3806636

I drew the curve for the rails by making a giant "compass" - I tied a piece of string to the leg of a chair, and then tied a pencil at the desired radius, then I drew a curve on a piece of 3/4" mdf. Then I moved the mdf 1 1/2" closer to the chair and drew another curve, so I ended up with two parallel curves 1 1/2" apart. Then I sawed the curved rail, traced it, and sawed the other curved rail. I screwed the two curved rails together and sanded them to the line with a belt sander.

The end rails are just maple scraps. The platform in the middle is 1/2" plywood with reinfocement rails on it. The platform is screwed between the curved rails, it's removable so you can flip the rails over and use them for either concave or convex carving.

View attachment 3806642

View attachment 3806643

The trick with this is sizing and positioning the platform between the rails such that your router has enough adjustability in terms of depth in order to actually get the bit down to the workpiece. I found that I barely had enough travel with my router to get the bit far enough down, it only sticks down about half an inch below the rails - I actually had to shim the bass up off the workbench to get it close enough to the router.

View attachment 3806644

I used the common 1 1/4" diameter Freud mortising bit that most people seem to use for router planing. It worked great. The surface was completely true and even and just needed final sanding.

Hopefully this helps people understand how the jig worked - let me know if there are any questions!
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So, pardon the zombie thread action, but I wanna do exactly this. I've been looking around TB for examples and this is one of the simplest designs. I wonder (and anyone else watching please chime in, I PM'd @dwizum but didn't hear back, maybe he's on a TB break...) how do you keep the router sled from twisting? Or does the curved surface keep it from wanting to twist right or left?
 
#189
Reedt2000 said:
So, pardon the zombie thread action, but I wanna do exactly this. I've been looking around TB for examples and this is one of the simplest designs. I wonder (and anyone else watching please chime in, I PM'd @dwizum but didn't hear back, maybe he's on a TB break...) how do you keep the router sled from twisting? Or does the curved surface keep it from wanting to twist right or left?
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Routing the convex surface? I did that recently on my still-unfinished WBO build and had the same concern about the sled going off square. It turned out not to be needed, at least in that case. Going off-square tends to make the sled rise off two of the four contact points, so its own weight tends to hold it down and square. And if it does go off-square anyway, that moves the router bit away from the surface so at least it doesn't harm anything.

That's true on a convex face, but I think it works the opposite way on a concave face so you may possibly run into trouble there. One way around it is to clamp stop blocks to the lengthwise rails of the fixture, on either side of the sled, constraining the sled to only move perpendicularly, make one cut, move the stop blocks, etc.
 
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#190
Max Bogosity said:
Routing the convex surface? I did that recently on my still-unfinished WBO build and had the same concern about the sled going off square. It turned out not to be needed, at least in that case. Going off-square tends to make the sled rise off two of the four contact points, so its own weight tends to hold it down and square. And if it does go off-square anyway, that moves the router bit away from the surface so at least it doesn't harm anything.

That's true on a convex face, but I think it works the opposite way on a concave face so you may possibly run into trouble there. One way around it is to clamp stop blocks to the lengthwise rails of the fixture, on either side of the sled, constraining the sled to only move perpendicularly, make one cut, move the stop blocks, etc.
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I appreciate the insights. Were there pics of your fixture in the thread? I followed it and I remember seeing the carve, but not the fixture.
 
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