Bridge Shaving question

[TommyK]

Could be my astigmatism, but there is more neck wood showing at the edge of the guitar (red arrow), than nearer the sound hole (blue arrow).

 

Could be what your guit tar tech is seeing that leads him to believe it needs a neck re-set. Not sure this is re real problem or just my eyes.

 

A similar shot down by the bridge, showing the flatness of the top would be helpful in diagnosing.

[TommyK]

Could be my astigmatism, but there is more neck wood showing at the edge of the guitar (red arrow), than nearer the sound hole (blue arrow).

 

Could be what your guit tar tech is seeing that leads him to believe it needs a neck re-set. Not sure this is re real problem or just my eyes.

 

A similar shot down by the bridge, showing the flatness of the top would be helpful in diagnosing.

[brians356]

Vourot,

 

You still haven't supplied the action measurements I asked for. Sighting down the fingerboard or laying a long straightedge on the frets and seeing where it "intersects" the bridge top is ok but an inexact science, and there can be a hump at the neck/body joint area that can interfere with this method. Measuring the string and saddle heights as I described are the best inputs.

 

If you can lay hands on the guitar and have a 6-inch rule that can measure 1/32", write down those figures and report them here if you can spare five minutes!

[Boston004681]

An AJ shouldn't need the bridge shaved.

[onewilyfool]

Personally my bridge has never had enough hair to require shaving......but I've been lucky

[vourot]

Brians356, when I went and picked up the guitar the tech went over everything with me including measuring pretty much exactly as you had suggested. String height right now is at 5/32+. We went over all my options and he said to do it properly a neck reset would be required then he said I should have bought a Collings! He could get the action almost to where it needs to be but it would only be postponing the inevitable.So I took it to another shop and they said the exact same thing, neck reset. At the second shop they had an AJ which I played and was very impressed with it. No issues with that one and the action was perfect. So, I am going to take it to the "Guitar Doctor" down in Bellingham ASAP and have the work done under warranty. If it turns out anything like the other AJ I played I will be truly happy.

[brians356]

Well I guess I am beating a dead horse at this point. The pics you posted do look like the neck angle has come up, and what two luthiers have said is evidence enough. I just saw this as a chance to illustrate how anyone with a 6-inch ruler (or measurements someone else has taken) can use simple geometry to determine if a neck reset is probably needed.

 

A rule of thumb that is a starting point (as long as a bridge hasn't been shaved!) is this: Take the string height at the 12th fret of any string (e.g. 3/32") and double it (e.g. 3/16".) This would be the "ideal" saddle height (above the bridge top) under that string. So if a guitar's action is 3/32" at the 12th fret under the low E string, but the saddle is also 3/32" under that string, it means the neck angle has increased enough above ideal that half of the available height adjustment has been lost. And the "drive" on the top has been reduced somewhat in order to get a low action. This example is pretty typical; few people would say such a guitar definitely needs a neck reset. It is "borderline." But if the saddle height is less than the 12th fret string height, it is a definite red flag. That's why I was so curious about your guitar's measurements.

 

Where this falls down is if the bridge has been shaved, because we are using the original bridge top as a reference datum for the ideal geometry. The common rule of thumb derives from this geometry (for flattops): The plane of the fingerboard should be tangental with the [original!] top of the bridge. Note that when this ideal neck angle exists, you would not run out of saddle adjustment unless and until you lower the action to zero height, i.e. until the strings are laying on the fret tops!

[ajsc]

"he said I should have bought a Collings!"

 

Just a few 1,000 more, & you wouldn't have this problem?

I think I would have told this guy what he should kiss!!

:)

[ksdaddy]

There are two methods I use to assess the neck angle. Both are valid and I try to use both, not just one, lest I be deceived by lighting or 48 year old eyes. Both methods require the truss rod to be fairly 'spot-on' with as little relief as possible or the results won't be as easy to see.

 

One is the method rar mentioned earlier in the thread, sighting down the neck like a rifle barrel and seeing where the fingerboard would hit the bridge if the fingerboard kept on going...... an imaginary line. I hope to see that point very high on the bridge. If it's halfway down the bridge, there could be trouble. Note I said bridge, not saddle. Ignore the saddle.

 

The second is a little controvertial but I invite anyone to try it.

 

Fret it at the first fret and also where it meets the body, typically the 14th fret. Note the gap or relief at the 7th fret. This is the relief provided or controlled by the truss rod. The truss rod has no effect past the 14th fret, at least not in normal guitars. Now fret it at the first and LAST fret. There shouldn't be any noticeable difference in the relief.

 

If the upper braces or neck block are collapsing the of course there are problems a neck reset isn't going to cure anyway, so that should also be part of the assessment.

[rar]

The second [method] is a little controvertial but I invite anyone to try it.

 

Fret it at the first fret and also where it meets the body' date=' typically the 14th fret. Note the gap or relief at the 7th fret. This is the relief provided or controlled by the truss rod. The truss rod has no effect past the 14th fret, at least not in normal guitars. Now fret it at the first and LAST fret. There shouldn't be any noticeable difference in the relief. [/quote']

 

I haven't heard of this one before, but it certainly makes a lot of sense! Is it your own invention?

 

-- Bob R

[ksdaddy]

No, I stole it somewhere.