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After a two year hiatus, caused by numerous distractions (including taking up scuba diving), a few days off between holidays inspired me to clean my shop and finally get back to build #2. The box had been closed up and sitting there waiting for me to get up the nerve to cut the binding channels. I need to accept that building this guitar is part of the learning process and likely won’t be perfect.

Well this afternoon I took my hand-held shop-built binding cutter which features two bearings to ride against the sides and a 1/4'” down-cut spiral bit, and I cut the binding channels on both the top and bottom. When I was finished, I found considerable variation in the width of the channel, so I ran the cutter over the guitar again, but without any improvement.

On closer examination, it looks like the sides were not flat and square in the areas where the channels were not deep enough. Using the two bearings riding against the sides where the sides weren’t flat and square seemed to be the problem.

So the question is: did I miss a step somewhere? Should I have squared-up and flattened the sides before I cut the channels? It seems to me that this may have been the problem I had with the first build where after getting halfway through the finishing process, the bindings are not a uniform thickness. I did square up the sides in the process of filling the grain with System Three epoxy and sanding it level. Did I get the process steps out of order?

I realize that a different binding cutter may have given me an improved channel thickness, but that wouldn’t solve the problem I had on the first build.

The usual order of things is to block sand the sides before routing the binding channels. It's pretty near impossible to get a good binding channel cut if the sides aren't smooth and flat (I discovered the same thing on my first guitar!). Any dips or flat spots cause problems down the road.

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http://www.PeakeGuitars.com

I started to block sand them this afternoon, and I wll try cutting the channels again after I get that done.

Thanks!
Matt

There you go Matt - good plan. Since the bearings on your jig register off the sides any imperfections with the sides will show up as imperfections with the binding channels.

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Ann Arbor Guitars

Fret not. I have it on very good authority that this step has been missed once before and the binding channels considerably improved once the sides were sanded flat and smooth.

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Eagles may soar, but weasels don't get sucked into jet engines.

The variation in width came from not keeping the common centerline of the guide bearings and bit perpendicular to the plane of the cut at every given location. Because the bit and the guide bearings do not occupy the same vertical center plane, if the common horizontal centerline gets out of perpendicular to the plane of the cut at a given location the width of the cut changes. Depending on the adjusted offset between the guide bearings vertical centers and the bit vertical center and the difference in diameter of the bit compared to the guide bearings along with if you are in an inside curve or and outside curve at a given location, the cut may be significantly deeper or shallower than intended.

This is a common error made when someone cuts binding channels for the first time with an adjustable guide bearing system. I will try to find the time here in the next hour to sketch out this issue on cad and post. Once you see what is happening it is easy to avoid in the future.

If you use a pilot type guide bearing where the guide bearing is mounted on thee bit shank this will not happen. However you use this type of system you have to have a method or fixture that insures that the vertical centerline of the bit stays parallel to the sides.

So you see both systems have trade offs

Matt my friend here is a tip for you that I learned from Grumpy/Mario.

Before taking a block to your sides to true them up cut a very shallow binding channel just deep enough to make the sides proud of the top and back plates. Then when you true up your sides you are not sanding the top and back plates too which makes it go much faster and easier.

After your sides and waist area are trued up then you cut your binding and purfling channels to the full depth that you want.

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Ann Arbor Guitars

here is what happens.


if the guide bearings are equal or smaller diameter than the bit then the error is to the over cut side

incosistancys of the side will be reflected as well if the guide bearings path flow over them but more often than not the error comes from not keeping the common centerline of the guide bearings and bit in plane with the cut plane as you go around the body

Michael,

Thanks for the great diagram. I do understand the limitation of the lack of a pilot bearing on the router bit. Although I was very careful to try to keep the bearing/bit perpendicular to the tangent of the curve, I do suppose it is not possible to be exact. I did shut the router off and looked at where the bit fell and swept the router back and forth a bit on both sides of the perpendicular, that is when I concluded it really looked like it was the lack of a flat square side that was causing my problem.

Anyway, I spent much of today flattening out the sides, and hopefully I will be able to try to cut the channels again tomorrow.

Thanks to all!

Matt