The Mudcat Café TM
Thread #152511 Message #3567379
Posted By: JohnInKansas
16-Oct-13 - 07:43 AM
Thread Name: Measuring string gauges...
Subject: RE: Measuring string gauges...
A micrometer should work quite well, and there are a couple of styles available that would be suitable. The traditional "C-Clamp" that screws a plug down against the part to be measured, usually a 0 to 1" range, works quite well, although some people have a tendency to screw down too tightly and on a small wire it's possible to flatted the part you're trying to measure - and also damage the "mike."
The "Caliper" type that has parallel jaws, with one that slides in a slot in the other to change the gap should work quite well for measuring strings, and may be cheaper in most markets.
"Feeler gages," as the term is used in the US, are a selection of metal strips of various thicknesses, and are quite useful for measuring the gap between two things, but very difficult to use for an accurate measurement of thickness or outside diameter.
Either kind of micrometer can be accurate to within 0.001 inches with a decent quality one. The better "C-Clamp" shaped ones can get easily to 0.0001, but most such require that you read a "vernier scale" to interpolate between 0.001 markings on the barrel, or sometimes have a dial indicator (that usually needs re-zeroing for each use). Caliper types commonly have a "dial indicator" (sometimes a vernier) built in and may claim finer resolution than more basic models, but in the quality commonly offered for sale at reasonable prices their limits are somewhat suspect beyond 0.001 unless you've paid big bucks for them.
BARE STRINGS can be measured as accurately as you're likely to need, since the wire diameter is the gauge. For wound wires it's a little more problematic.
The wire diameter increases for a bare wire as the intended pitch goes down. Most instruments are designed to hold a fairly specific tension, pretty much the same for all the strings. As the strings get smaller, the tension gets lower, and for small (high pitched) strings that's not really a problem. The core wire, for the most common materials, needs to be above about 60% of yield strength, up to about 80%+, in order to "resonate" well in a plucked string like on a guitar; but this limit is less applicable for a bowed string - hence the ability to use "gut" strings more easily there.
The requirement for a fairly specific tension> in all the strings above a particular "weight" (below some pitch) dictates that all wound strings intended for a particular kind of instrument will have very similar core diameters.
ALL WOUND STRINGS have a core wire sufficient to cary the intended tension, and in many cases the core diameter is pretty much the same for all the the wound strings on a given instrument. The weight per unit lengt is adjusted by wrapping wire around the core to change the pitch. The "winding" theoretically should not affect the tension or flexibility of the string on the instrument for which it's intended.
Since different wound strings may use different materials for the winding, and diffent wire profiles, the outside diameter measured over the winding may not be really representative of the "effective gauge" of the string, although variations for similar strings intended for the same kind of instrument probably don't vary enough to make much difference. Various sellers may have slightly different meanings for their usage of the term "gauge."
For good sound, the most critical thing is that the sring must be absolutely constant in diameter and weight per unit length. A lumpy string never sounds good. For wound strings not purchased and used promptly, the lumps may be due to dirt and/or corrosion inside the winding where it's not easy to tell its there, so the "spares" that have been in the case for a few years may be a little disappointing when you have to put one on.
John