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Millimeters in an inch
http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=44219		 Page 1 of 3
Author:  Tom West [ Thu Sep 25, 2014 9:42 am ]
Post subject:  Millimeters in an inch
Anyone ever notice how many M.M.s there are in an inch. Does it have any relationship to one of our most popular scale lengths for steel strings...?
Tom
Author:  doncaparker [ Thu Sep 25, 2014 10:00 am ]
Post subject:  Re: Millimeters in an inch
No, I think it is just a coincidence. Take the standard scale length to which you refer (25.4 inches) and multiply it by the number of millimeters in an inch (25.4) and you get 645.16 millimeters. That is not a convenient, round number.
Author:  Colin North [ Thu Sep 25, 2014 1:27 pm ]
Post subject:  Re: Millimeters in an inch
I thought it was 25.34 inches?
Author:  wbergman [ Thu Sep 25, 2014 3:13 pm ]
Post subject:  Re: Millimeters in an inch
Everywhere I check it is 25.4 exactly, but I am always ready to be corrected. Is there another reference out there with a different conversion?
Author:  bluescreek [ Thu Sep 25, 2014 3:18 pm ]
Post subject:  Re: Millimeters in an inch
25.4 is the number
Author:  murrmac [ Thu Sep 25, 2014 3:28 pm ]
Post subject:  Re: Millimeters in an inch
bluescreek wrote:
25.4 is the number


John, we've just been through all this on the UMGF !

EDIT : just realised that there may be some confusion here ... Colin was talking about a guitar scale, not the number of millimeters in an inch ...
Author:  Mike OMelia [ Thu Sep 25, 2014 3:36 pm ]
Post subject:  Re: Millimeters in an inch
Just where exactly does the scale length come from? 25.4 seems odd when you stop and think about it. Wikipedia talks about METRIC ranges from 645 to 660 mm. Lots of European influence. 645/25.4 gives 25.39, or 25.4. My guess is someone chose 645 mm years ago. Specifying sub-milimeter makes little sense for a structure like a guitar (size wise).
Author:  murrmac [ Thu Sep 25, 2014 4:02 pm ]
Post subject:  Re: Millimeters in an inch
Mike O'Melia wrote:
Just where exactly does the scale length come from? 25.4 seems odd when you stop and think about it. Wikipedia talks about METRIC ranges from 645 to 660 mm. Lots of European influence. 645/25.4 gives 25.39, or 25.4. My guess is someone chose 645 mm years ago. Specifying sub-milimeter makes little sense for a structure like a guitar (size wise).


I wouldn't think that early standardization would have been formulated in metric terms. Spain, for example, did not adopt the metric system until 1849, by which time Torres had already been building for some years. My guess is that he adopted 25.6" as the de facto scale length for a classical guitar, rather than 650mm, which is chosen nowadays because it is a nice round number, but IMO is coincidence.

Martin would certainly have formulated their scale lengths in inches rather than in millimeters.
Author:  RustySP [ Thu Sep 25, 2014 4:25 pm ]
Post subject:  Re: Millimeters in an inch
My StewMac Martin long scale fret rule says 25.34"
I am gradually switching over to metric, just seems a whole lot simpler.
Author:  Joe Beaver [ Thu Sep 25, 2014 4:32 pm ]
Post subject:  Re: Millimeters in an inch
I've always figured the Martin scale was actually 25.34 (2X the distance from the nut to the 12th fret) but was referred to as 25.4 because that was about where the saddle went after compensation.
Author:  David Newton [ Thu Sep 25, 2014 4:51 pm ]
Post subject:  Re: Millimeters in an inch
How many leagues are in a mile?
Author:  wbergman [ Thu Sep 25, 2014 7:12 pm ]
Post subject:  Re: Millimeters in an inch
I find a reference of 3 miles in a league.
Author:  Lonnie J Barber [ Thu Sep 25, 2014 8:34 pm ]
Post subject:  Re: Millimeters in an inch
I use mm also much easier to read,remember,etc.


Sent from my iPhone using Tapatalk
Author:  Colin North [ Fri Sep 26, 2014 6:15 am ]
Post subject:  Re: Millimeters in an inch
wbergman wrote:
I find a reference of 3 miles in a league.

Not wanting to be pedantic (sic) but, "3 miles in a league" refers to nautical miles
1 (land) mile = 0.289658747 leagues.
Sorry, I've become a bit of a :ugeek: since starting to build guitars.
Maybe I should change my username to Sheldon...
Author:  David Collins [ Fri Sep 26, 2014 7:59 am ]
Post subject:  Re: Millimeters in an inch
Best explanation I've been able to come up with is that their scale lengths were originally reasonable round numbers of 25" and 25.5". Since Martin used to use the true "rule of 18" through the late 70's however, the final lengths end up shorter than they would with the 12TET spacing based on the 12th root of 2.

When they switched to the modern spacing, in order to keep their total lengths the same they simply shortened the base numbers to 25.34" and 24.84", giving them a slightly different fret spacing but maintaining the same final string length.

The listed numbers of 25.4" and 24.9" have never actually been used for any scale length calculations, but are simply single decimal rounded specs to be listed. It is loosely justified by saying that their description of scale length includes an average amount of compensation, but they are pretty much alone in this definition, and for all practical purposes these numbers are just rounded specs.

For more in depth discussion from the archives -

viewtopic.php?f=10101&t=37957&p=497710
Author:  Dave Fifield [ Fri Sep 26, 2014 5:54 pm ]
Post subject:  Re: Millimeters in an inch
1 inch = 25.41mm, not 25.4mm.....just sayin'..... :ugeek:
Author:  weslewis [ Fri Sep 26, 2014 6:03 pm ]
Post subject:  Re: Millimeters in an inch
about this much!!!!!! [:Y:] [:Y:]
Author:  dnf777 [ Fri Sep 26, 2014 6:43 pm ]
Post subject:  Re: Millimeters in an inch
I got used to using metric measurements when making violins, and find it so much easier to use. Millimeters are all you need essentially to cover the entire scope of most instruments. No fractions! :-)
Author:  Clay S. [ Fri Sep 26, 2014 7:46 pm ]
Post subject:  Re: Millimeters in an inch
"Millimeters are all you need essentially to cover the entire scope of most instruments. No fractions! :-)"

When I use millimeters I usually guesstimate 1/2mm's and 1/4 mm's. A mm is not that precise of a measurement, but by using the spaces as well as the lines you can get close enough.
Author:  murrmac [ Sat Sep 27, 2014 1:57 am ]
Post subject:  Re: Millimeters in an inch
Millimeters are useful in their place, (that place being in cabinetmaking and kitchen-fitting IMO) but have less of a place in guitar measurements (again IMO).

I like it that my nuts measure 1 3/4" , I don't want them to be 43mm or 45mm or whatever.

The beauty of the imperial system is that when exactitude is required, like in measuring action, and figuring out how much to remove off a saddle, or working out exact nut slot location for equidistant string spacing, then thousandths of an inch is a perfect unit of measurement for being as exact as you realistically need.

What does make me grit my teeth is when people talk about action height in terms of 1/32" and 1/64"... .001" is the way to go.
Author:  bluescreek [ Sat Sep 27, 2014 6:39 am ]
Post subject:  Re: Millimeters in an inch
You can see the generation separation here. Most of use old guys are used to the inch foot and yard it comes down to what you are used to and what you can work the best with. As a machinist I am used to the thou but microns works well too
Author:  Lonnie J Barber [ Sat Sep 27, 2014 9:51 am ]
Post subject:  Re: Millimeters in an inch
I'm an old guy but new to such precise measurements. So I find mm's much more simple to use. Now if I was a machinist then I too would find thousands. Of an inch much less intimidating.


Sent from my iPhone using Tapatalk
Author:  Jfurry [ Sat Sep 27, 2014 10:14 am ]
Post subject:  Re: Millimeters in an inch
We use the thous. At the shop. I thought when I got my own shop together I would change to mm. At this point in time ill stay imperial
Author:  David Collins [ Sat Sep 27, 2014 10:23 am ]
Post subject:  Re: Millimeters in an inch
Honestly, both systems suck - imperial because it evolved with no clear intention or engineering and ended up a garbled mess of irrational proportions. Metric on the other hand, sucks because it's built on the stupid base-10 numerical system we use simply because we have 10 fingers. You can't even halve a unit more than once without going past one decimal point, much less deal with thirds, sixths, and other rational ratios. If we had built our numerical system on base 12 (or even better 24), then metric would be more practical. As it is now, all we have to choose from is dumb and dumber (not sure which is which).

In practice I find thousandths of an inch a more reasonable sized unit for precision work on our scale, and 1/64" of an inch to be about the perfect dimension to still be reasonably viewed by eye on a scale. In theory it's far from ideal, but in practice I find it to be more visually ergonomic than 1 or .5mm marks.

For carpentry work, I would prefer we switch to "the Bob" as a unit.

In any case, the original topic was on how Martin arrived a the seemingly odd scale length numbers of 25.34" and 24.84" (or 25.4" / 24.9" as they call them). For this it doesn't matter what we prefer, but rather what system the makers were most likely to be using at the time they established these lengths. It appears that they started with simple 25" and 25_1/2" base numbers, but their primitive spacing formulas left the final lengths short at a less intuitive spec.
Author:  Tom West [ Sat Sep 27, 2014 10:46 am ]
Post subject:  Re: Millimeters in an inch
Dave Fifield wrote:
1 inch = 25.41mm, not 25.4mm.....just sayin'..... :ugeek:



Dave: Are you sure about that.........?
Tom
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