Official Luthiers Forum!

Hi

I have routed the channels for bindings and noticed on the back at the upper bout the channel goes really shallow(nearly half the depth lost).
I have dry fitted and looks bad, weird as the rest of the back is fine and is a constant radius. I am using a laminate trimmer with adjustable base camber which is adjusted to stay parallel.

2 questions

What caused this and suggested remedy, I will add its Bog Oak and hard as steel so not sure about filing the channel but will if its the best option

TIA

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Why not run your router over the areas a few times to get them to deepen? Alternatively, a file with a safe edge can deepen the channels without making them wider

Ed M

I usually get a small amount of this same problem (though not as extreme) on my back upper bought as well. I use a laminate trimmer, but I made a jig that functions similar to the LMI one that "floats" vertically supported by springs. If my sled that holds the body isn't adjusted so that the body sides are all perpendicular with the workbench the problem does get pronounced and I have to adjust and run the cut again.

How flat are your sides?

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

+1 for Occam’s razor. The sides may not be flat.

If they are, your cutter may not be cutting full depth depending on the angle of attack. Make sure the jig is perpendicular to the side at all times. It’s easy to go askew with it.


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Do you have a photo of the laminate trimmer set up you are using? I'm having a hard time picturing how this could happen if your sides are flat. My set up is one of those towers and the depth of cut is set using the cutter and bearings from StewMac. I get almost no variation in the depth of the cut. It's remarkably consistent in fact down to a few thousandths.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Seem okay Trevor, I had another go and set the angle sharper and seems to of cured it thanks

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we need to know your process

router cutter you use
the way you set up to cut your channel

we need to see if this is a technique or tooling issue

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

That sounds like a win. Well done!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I don’t even know what “set the angle sharper” even means I better look at my set up too, just in case.

Hope you keep us posted with the build progress.

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Time you enjoy wasting is not wasted time.

I as suspecting if you used a router without any modification the router learns from the back taper.
if you have a binding jig you didn't set it up properly
be sure to post pics of your technique so we can help

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it