Half-shim a classical nut?

AgedAngel · #1 10-21-2018, 03:47 AM

I have a bit of back buzz on my low A when playing a fourth fret C# together with a B-flat on the third string. In general, the nut height is quite nice, and I would not like to mess with it overall. Would it do anything terrible to the nut if I used a shim (paper-thin) on the bottom three strings alone?

Thanks for any suggestions.

AA

MC5C · #2 10-21-2018, 07:19 AM

A shim won't do anything to the nut except raise it a bit in a totally non-invasive, reversible way. I'd use a full length shim and raise the whole nut, rather than try to tilt it. You'll raise the nut around .004", which is a very reasonable step to try. If you want, you can just slide a piece of paper under the A string and see if raising the string that much makes any difference. With any back-buzz, I first look at the frets to be sure they are level, usually one is slightly too high or low and is causing the buzz, leveling the frets takes care of it. If the nut is indeed too low, usually you get a buzz when playing the open string - either a straight out buzz, or a rattle if you pluck with any power at all.

AgedAngel · #3 10-21-2018, 09:46 AM

Thank you. I appreciate the input.

AA

M Hayden · #4 10-21-2018, 10:07 AM

I agree that sliding a piece of paper into the A string slot will quickly determine whether or not it helps. Also, you might get a few straightedges and do the rocker test to determine whether there’s a low/high fret.

Mooh · #5 10-21-2018, 10:07 AM

I've laminated a piece of bone to the underside of a nut and sanded it to within a very fine tolerance on my 1" belt sander to a wedge shape. With well matched material clamped well with the appropriate amount of glue, the glue line will be virtually invisible and there won't be any auditory change in the instrument.

AgedAngel · #6 10-21-2018, 11:05 PM

Quote:

Originally Posted by Mooh

I've laminated a piece of bone to the underside of a nut and sanded it to within a very fine tolerance on my 1" belt sander to a wedge shape. With well matched material clamped well with the appropriate amount of glue, the glue line will be virtually invisible and there won't be any auditory change in the instrument.

I envy you your tools and your expertise. My own efforts are limited to sanding down a saddle.

As it turned out, I just went ahead and shimmed the entire nut. Took about fifteen minutes. And I discovered a small object lesson while I worked: the gentleman who sold me the guitar had had a custom nut and saddle worked up for the instrument, and he included the old nut and saddle and a couple of nut shims (one of which I used) along with the instrument. I noticed that there was a half-shim among the shims...and also noticed that the original nut had a hairline crack exactly where the half-shim would have ended.

So...half-shimming is indeed probably not a good idea.

Thanks to all for the suggestions, information, and help.

AA