Official Luthiers Forum!

Interesting. I haven't noticed any depth reduction, and I haven't chamfered any inside corners on any of my binding.

That hasn't been an issue for me.

I actually don't like the idea of an inside bevel, why reduce the gluing surface area?

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Old growth, shmold growth!

I'm on my second StewMac cutter, at over 100 instruments between the two. Haven't worn out a bearing, yet.

If I think a top will be splintery(after a while, you get a feel for wood...) I'll cut the top's purfling channels with a 1/4" downcut spiral bit using a hand held Porter Cable 310, with a simple wooden "finger" clamped to the base as a bearing/guide. Works great, costs nothing. There isn't any taper to the top's surface, so a hand held router works just fine for the purfling channels. I've never experienced a situation when routing a back that required a spiral bit.

I also don't like the idea or the bearing being so far away from the cut; even the best factory acoustic guitars have sides that are slightly less than perpendicular, and often slightly "wavy", enough so that the cut will not be true every time. Bearings are also a much quicker method of changing the cut depth, and 100% consistent, every time, where you'll be adjusting, and making test cuts, adjusting, more test cuts, etc... for every. single.cut. with the above system.

Anyone have a source for bearings for the stew mac rig? Need some intermediate sizes that they don't sell. Have wraped with tape to build up diameter, but would prefer the proper size bearing.

I'm with you all the way on this.

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Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

No, I just took my latest acoustic out and measured it. It's exactly 3/16th's in height all the way around the back of the instrument at all the 20 or so points of measurement that I measured. That's exactly the height it was when I made it, so my binding ledge was absolutely consistent to the binding all the way around the instrument.

But I agree, if it WERE there, I would likely consider it irrelevant as well and likely wouldn't true it up.

So what causes that for you guys? Does it have something to do with the sliding carriage system? Just curious.

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Old growth, shmold growth!

I just think that the bottom edge is already thin enough, chamfering it would reduce it further. If binding is 3/32 wide and the chamfer removes even as little as 1/64th of an inch, that would actually be roughly 15% of the gluing surface area of the bottom edge.

But I guess it doesn't really matter though, it's not going to come unglued.

To each his own!

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Old growth, shmold growth!

I forgot to mention that I'm extremely nearsighted. I can read the microprinting on check signature lines.

No kidding.

At that magnification 3/16th might as well be a foot, it takes up my entire field of view.

So yes, I can see exactly where the binding lines up to the ruler, exactly in the centers of the black index lines.

Yes, zero variation.

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Old growth, shmold growth!

Ah, standard practice for cabinetmaking.

OKay, I can see that, if indeed it's not truly structural on an acoustic guitar.

However, I notice a difference in response of the box when I rout for bindings, that is restored somewhat when tghe binding is glued.

To that end I've endeavored to develop as tight and complete a binding ledge joint as is humanly possible, to minimize the possible impact of routing for bindings, to the best of my abilities.

That's one reason Ive started making my own bindings, as I've been unhappy with the trueness I get from manufacturers.

Maybe it's in my head, but I think every bit adds up to a whole.

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Old growth, shmold growth!

The issue is not your eyesight. It's the fact that you are using a ruler to measure. That's not an accurate enough form of measurement to detect the variation.

Sure it is. Even if the ruler is not exactly 3/16th, the distance between the two points of measurement stays the same at that point on the ruler, so I can detect whether or not the binding is that particular distance. It lines up on the center of the black index marks. They're not very wide.

I can see a thousandth of an inch difference with my eyeball at that distance no problem.

Hard for you to believe, I know.

But just so you are aware I got my dial caliper out, measured it, same result. .190 all around.

I measured a point, locked the caliper, checked all around.

Frankly,I'm a little surprised myself, considering that the final sanding shoulkd have likely caused a s little more variation, but no.

I'm very careful about that too, though.

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Old growth, shmold growth!

I'm sorry but you cannot see one thousandth of an inch with your bare eyes. If you really could then I want you to come work for me. I'll save a fortune on measuring tools.

My eyes are like magnifying glasses.

A thousandth of an inch is the thickness of a sheet of paper.

I can see that easily.

It actually comes in very handy when adjusting nut slots and other tasks that require close vision, such as fret polishing and other tasks.

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Old growth, shmold growth!

what can you see with a magnifying glass?!? That would be like a microscope!

Okay, a microscope then.

When I was a small child and my eyes were more flexible, I could actually see onion cells.

Onion cells are very large though, comparatively.

Blind as a bat otherwise.

Can't do that anymore though, as I'm getting older and the lens has progressively stiffened some, but I can still see the paper thickness increment.

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Old growth, shmold growth!

Paper is typically .002"-.003"

Not the one I measured.

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Old growth, shmold growth!

Trevor Gore recommends it in his book as well.

A few other advantages to the slight chamfer is that the first point to wear on the router bit is the very edge, such that most channels are actually slightly chamfered and not as sharply defined as you think. And finally, there will likely be some fine dust or other foreign matter that will make its way into the channel as you're gluing the binding, and the chamfer gives this stuff a place to hide instead of hindering the fit, leading to better fitting bindings.

How do you guys make the chamfer?

I was playing with some scrap binding material yesterday using my block plane and couldn't quite find the right way to hold the material.

Easier to do before bending, but I've done it after as well. Just hold the binding in one hand and run a sharp razor blade (as in, mini scraper) along the edge of the binding. It's not difficult to get uniform results along the full length of binding.

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sweat the small stuff.