Al.
...When the bridge height varies, the string break angle does as well,
That assumes saddle height has remains constant.
String
break angle is a function of
saddle height, the saddle height is adjusted to yield the maker's action height spec but within the small variation in bridge heights the saddle is normally tall enough to give a good break angle.
Bridges are shaved to allow saddles to sit clear enough of the bridge to bring back some break angle to otherwise too-low saddles, but that then brings on the risk of a split bridge when/if the saddle slot is deepened to keep it from leaning forward too much under string tension, no?.
The result is usually still a compromise since the ideal combined bridge/saddle height which is supposed to allow for max string energy transfer to top is now less than the 1/2" "ideal"
(which probably also varies according to scale length)
which does have some effect on the string pressure being applied to the top, as does the overall weight of the bridge. Granted, all of this is probably minor, but it will result in deviation from the original guitar design, and makes each guitar have some variation in overall tone. I am not saying that this is large, but it is there, and may contribute to some guitars being "excellent", while others of the same model are merely "good".
Makes sense to me.
When it comes to resets, I don't like it when bridges are shaved due to the loss of the reference point. A person looking at a perspective guitar purchase can sight down the neck (or use a straight edge) and see that the neck angle looks fine.
And that's why the alignment check is only valid if the bridge+saddle height is reasonably in the neighborhood of 1/2"; because we've discussed before that the alignment check can be "fooled" by a shaved bridge and I'd say anything more than 16th under that ideal 5/16" bridge height is cause for closer examination.
From here:
http://www.frets.com/FretsPages/Musician/Guitar/Setup/NeckAngle/neckangle.html :
"This diagnostic method is very clear, but it doesn't account for the thickness of the bridge. If the bridge had been cut low in an effort to forestall neck angle work, then the straightedge might land right where it belongs on top of the bridge, but the neck angle may be less than ideal. I could measure the height of the bridge (not including the saddle) and hope that it's somewhere between 5/16" and 3/8," or I could use an even simpler method to check neck angle."
"If there's less than 3/8" between the string and the top, then there's neck angle trouble:"
"If the strings are this close to the top, it means that the saddle and/or bridge have been seriously lowered to compensate for a "shallow" neck angle."
My D25's about a 32nd
under as built, and the '40's about that much
over.
All of which is easily compensated for with saddle height and still yield good break angle, although with mine the combined heights are also approx. 1/32nd over/under as saddle height remained same but action is still factory 6/64th on bass E.
BY which one can deduce neckset angle on the '40 is little "steeper".
The converse is that some people have said about a piece posted for sale: "oh, the saddle's low, must need a re-set" when in fact the bridge height should be checked first, as the saddle is commonly shaved to lower action simply to suit an owner's preferences.
If they are fairly new (leaves out most of the members of this board), they may not realize that the bridge has been shaved. They bring it down to their luthier to have it set up, and the luthier tells them that the guitar needs a neck set AND a new bridge to boot.
Fair enough and I agree a shaved bridge is something that should be disclosed if the guitar's being sold (if the seller knows it), but this comes back to my original statement that I only see it as a viable alternative in limited circumstances: for a guitar for which the cost of a reset could never be justified except for "sentimental" reasons and/or to maintain playability until the owner can afford the full reset, with knowledge the bridge will need to be replaced at that time, too.
I realize now I should have been clearer that I meant this is for owners who intend to keep the instrument.
There's a lot of guys here who only have one, and I certainly wouldn't condemn 'em for shaving a bridge so they could at least keep playing until the could afford a reset on a guitar they never intend to sell, that's all.
I had this happen when I bought one of my first guitar purchases (a Lys L-18CW). The bridge was made of the darkest, most uniform piece of black ebony that I had ever seen; so black it didn't even look like wood, looked more like matte black plastic. I had the neck reset, and the bridge replaced.
Don't know about the inherent value of that guitar but yes it's definitely a shame to have to scrap a beautiful piece of wood like that. And for that I definitely agree it was probably a bad idea.
None of this is the only way to do things, just my own opinion.
Yeah our attitudes about the operation aren't mutually exclusive, and again I was only pointing out that I came around to seeing a couple of justifiable reasons for shaving a bridge but both of 'em were predicated on the owner intending to keep the instrument and genuinely needing to resort to the economy measure.
Counterpoint, sure it's entirely possible for a piece like that to wind up in an estate sale before the owner ever got the chance to get the reset done.
But if it wound up in Frank Ford's hands, or somebody like him, I suspect they would actually have enough brand knowledge to know what the original factory spec was for bridge height or else they'd resort to the generally accepted 1/2" combined b/s height.