Treeline
New member
I'll weigh in on the metal / wood expansion thing.
Metals are good conductors of temperature, and each will have its own coefficient of expansion. So they tend to respond quickly and evenly to temperature changes. I expect that you will find, though, that the degree of expnsion with change in temperature of nickle-silver alloy (fret material) is pretty minimal. You're not likely to notice it at all, in fact, because the wood in which the fret is laid remains a bit elastic.
[I do know that chunks of milled steel about a foot long will expand or contract a few thousandths of an inch at the most with a change in temperature from a warm machine shop (where they were made to spec) and a cold winter warehouse (where the QC guy almost got the machinist fired for cutting them too short). Mystery was solved when they moved all the steel back into the warm shop and remeasured the units the next day].
What's at work here can be something else, and that is the ability of wood to take on and release moisture because of the change in relative humidity that accompanies a change in ambient air temperature. Hot air can hold more water than cold air. When wood gets cold, it dries out. In doing so, it will contract - a lot. A top can shrink as much as 1/8 " before it starts showing signs of stress. Thats a big number. A top that stays loaded at 10% R.H. is likely to split.
For everyone who's gotten raw fingers in the winter with those sharp fret ends that don't seem to bother in the summer, well, it's the fingerboard contracting as it dries out. Frets don't do that. [Probably means the instrument has been refretted, too, but that's a tale for another day].
So now apply these concepts to a laminated beam with one side finished, the other unfinished, and subject to constant stress. It's a wonder necks don't bend more. The truss rod is usually a two - way rod that, when tightened, acts to induce a reverse warp in the neck. Neck warping under tension? We make it better by adding a little more...
Hope it helps.
Metals are good conductors of temperature, and each will have its own coefficient of expansion. So they tend to respond quickly and evenly to temperature changes. I expect that you will find, though, that the degree of expnsion with change in temperature of nickle-silver alloy (fret material) is pretty minimal. You're not likely to notice it at all, in fact, because the wood in which the fret is laid remains a bit elastic.
[I do know that chunks of milled steel about a foot long will expand or contract a few thousandths of an inch at the most with a change in temperature from a warm machine shop (where they were made to spec) and a cold winter warehouse (where the QC guy almost got the machinist fired for cutting them too short). Mystery was solved when they moved all the steel back into the warm shop and remeasured the units the next day].
What's at work here can be something else, and that is the ability of wood to take on and release moisture because of the change in relative humidity that accompanies a change in ambient air temperature. Hot air can hold more water than cold air. When wood gets cold, it dries out. In doing so, it will contract - a lot. A top can shrink as much as 1/8 " before it starts showing signs of stress. Thats a big number. A top that stays loaded at 10% R.H. is likely to split.
For everyone who's gotten raw fingers in the winter with those sharp fret ends that don't seem to bother in the summer, well, it's the fingerboard contracting as it dries out. Frets don't do that. [Probably means the instrument has been refretted, too, but that's a tale for another day].
So now apply these concepts to a laminated beam with one side finished, the other unfinished, and subject to constant stress. It's a wonder necks don't bend more. The truss rod is usually a two - way rod that, when tightened, acts to induce a reverse warp in the neck. Neck warping under tension? We make it better by adding a little more...
Hope it helps.
