Official Luthiers Forum!

There are some pretty ingenious folks here!

Don't get me wrong, I love hogging out carved double bass plates by hand but I was wondering if anyone has an idea for a thicknesser. The drill press hole method to determine the correct depth really doesn't work out too well for me either. The plate is too big to wrestle with one hand as I use the other to rotate the drill press depth handle. And I don't want to build a duplicator because I never make the same thing twice. I am thinking vagulely about something that might use a router, on rails with some type of depth limiter that could be a stylus following the already carved topside of the plate. I'd like to get accurate to about a 1/4 mm or so.

Or maybe the router or a grinder with chainsaw cutter (Excaliber) could be mounted on a beam with a wide enough span for the whole plate to be able to move freely underneath it. A smooth rounded "mushroom" pad could be below it for the plate to ride on as it is slid back and forth or in and out as the cutter hogs out wood.

Am I nutz?

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Ken

Ken, even if you make a wide variety of plates, you can still rough out the inside quickly (after the outside is shaped) by suspending a router over a dowel pin. This will give you a uniform plate thickness to refine by hand, but much of the grunt work is done.

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Dave
Milton, ON

250 microns?!?! That's 1/100th of an inch....only CNC will get you that close.

You need some kind of overhead or pin router...even so, with the bit going at 15,000 rpm I fear for your workpiece if the bit grabs. I'd almost lean toward using a Saf-T-Planer on a drill press, but you'd need one with a really deep throat.

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The member formerly known as erikbojerik....

I've been hearing more and more about bass builders using chainsaws to rough out their plates. Find a guy in your town that carves bears and beavers out of stumps. (Travers City. There's probably one on every block ). These guys can get pretty accurate. I'd probably consider a Lancelot though. I know of several arch top guitar builders who use them.

Your question, however, is on the final thicknessing. I can't imaging that you will be able to get nearly the accuracy you need with any simple drill press method. You'll alway have to touch it up with the Ibex plane.

This would probably work fine for me. That is what I am after. I will always finish with a hand scraped finish.

Got any photos of this kind of operation?

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Ken

I do use an excaliber carver and like it for hogging out, but I would like to get a uniform 10 mm or so without stopping and measuring all the time. These are big plates, keep in mind.

+- 0.25mm not micrometers.

Does anyone have a photo of their thicknesser? What bit is best?

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Ken

Erik was correct, you're talking 0.01". Most guys running wood on a CNC router are barely
getting that tolerence, if at all, on 3D work.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Oops , sorry Eric, didn't mean to dis you. It appears that Bob straightened me out. Well... a quarter of a mm seems to be pretty big in my book when I am graduating my plates. Okay then how about a half of a mm?

What kind of bit? I have a box core bit that looks like it might do the trick.

I will see what I can come up with. One of the big problems with this is that dust collection is difficult.

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Ken

I use John Sargent's duplicarver design & use the pin router technique as the second step for archtop plates (also using a core box bit). I don't try for anything closer than .030" from my target. (You have to remember that if the cut surface is anywhere off perpendicular to the cutter axis - i.e. if you're holding it tilted in any way - the cut is deeper. Trying for unrealistic tolerances will end in tears.)
Yes, dust is an issue!

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Dave
Milton, ON

Thanks Dave,

I will probably use my grinder chainsaw for the very rough part but then move on to the pin router technique. Do you have a photo of your pin router set up? I would like to gather some ideas from an existing design.

Honestly, I thought I was being conservative by suggesting 1/4 mm. I guess I was thinking something like " that's 4 or 5 passes with a finger plane" or something. Oh well, silly me.

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Ken

Sorry Ken, no pics. Go to "tool plans & pics" in MIMF library for full details on the Sargent duplicarver (also other stuff there on pin routers).

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Dave
Milton, ON

Yes Dave it just looked it up and Jim Combra's pin router will work fine. I will have to increase the depth max and beef it up a bit. Thanks.

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Ken