caliper

[johnakay]

digital caliper/vernier question.
I've had a couple of Chinese digi calipers.
the problem is that it doesn't show what I need.
when setting frets distances example...37.0457mm I can only get 37.00 or 37.1.
not sure if the .0457mm make much difference,
if the stewmac calculation states 32.758mm I just make it 32.7mm.
I'm not clued up on these.
I just make cigar box guitars to keep me occupied during none biking seasons.
can you get calipers with these type of measurements.
having said that I don't really want to pay a small fortune for one.

 

[Memmeddu]

digital caliper question.
I've had a couple of Chinese digi calipers.
the problem is that it doesn't show what I need.
when setting frets distances example...37.0457mm I can only get 37.00 or 37.1.
not sure if the .0457mm make much difference,
if the stewmac calculation states 32.758mm I just make it 32.7mm.
I'm not clued up on these.
I just make cigar box guitars to keep me occupied during none biking seasons.
can you get calipers with these type of measurements.
having said that I don't really want to pay a small fortune for one.

You don't need calipers, you either need 0.001 micrometers, gauge blocks a 0.001 indicator and a granite surface plate

 

[RichardM]

Metric, four decimal places!

 

[m_c]

Any decent caliper, even of Chinese origin, should manage 0.01mm measurements.

However, within a couple tenths will be more than good enough for guitar frets.
Guitar fret positions are far from perfect, and tune is greatly influenced by the player. How hard they fret, and play the strings has an effect on how in tune any given note is.

If you want to get geeky about guitar frets, have a search for True Temperament frets, which aim to compensate for how each string reacts to each fretting position.

 

[voipio]

A decent digital caliper should be able to resolve down to 0.01mm, or 10 microns, or about one fifth of the thickness of a human hair. If the cheap Chinese calipers you have won't give repeatable readings to 0.01mm resolution, and don't show the ability to increment by 0.01mm at a time when moved carefully, then chuck them out and get a decent caliper. Having said that, the positioning accuracy of frets in a wooden guitar neck isn't going to come even close to that, what with the thickness of the scribing tool tip, and the errors introduced when sawing a slot for a fret. There will be a host of other factors that will change the effective length of the string anyway, such as playing style, guitar construction and its mechanical behaviour under tensile stress.

The smallest change in musical note discernible by a human is about 25 cents, or about 1/4 or a semitone. That is equivalent to 1/4 of the distance between frets, and should give some idea of the accuracy required.

 

[Misterg]

not sure if the .0457mm make much difference,

It won't. 0.1mm is plenty accurate.

Eyeballed to better than 0.5mm works fine provided you measure all the fret positions from one end (0-1, 0-2, 0-3, etc. rather than measuring 0-1, 1-2, 2-3).

 

[johnakay]

ok thanks. as for eye balling is even worst.

 

[Misterg]

I've used a long steel rule taped to the slotting jig under under the neck blank and read the measurements off against a razor blade fixed to the end of the blank.

Dunno if you can make it out:

(Made the last one on my CNC though.)