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What type of rules or scales do you prefer for guitar building? How exact do they need to be? Do you use mm's, decimal inches, fractional inches, what combinations? What increments are needed - 64th", .1mm? How long are they?
I'm going to start building #5 in the next month or so, and thought I'd get some rules or scales (some refer to the very accurate ones as "machinist scales" - but I don't want to bog down in names if it can be avoided) buying one every couple of weeks or so.
My thoughts are to have one that is 6", 2 ft, and 3 ft. As I might start making some classical guitars, it might be good to have Inch/Millimeter on one or more of them.
Is it more important to use the same measuring scale - is it enough to use the same one if you do it the same way all the time?
I'd appreciate insight on what you choose and what makes you choose a particular type or brand.
Thanks in advance.
By the way, what brought this on is that my eyesight has been changing over the past several years, and I couldn't see accurately enough anyway, and although I tried to be very precise, often it was hard to see enough detail for precision. I had cataract surgery this past Mon, and will have the other eye done tomorrow. Gosh what a difference. I won't be going overboard on this, so if there's such a thing as too much precision, I won't go there. Oh, I do recommend the surgery if you have cataracts. It's very, very safe and the whole world looks way better to me than it did a week ago.
Bob

Edit: corrected the title

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Bob
From the oldest town in Texas.

For the smaller stuff, if you haven't already got one, a 6"/150mm digital calliper will save a lot of eye strain. Probably the most used tool in my shop.

In these parts its easy to get rules that are inch one side and metres the other, but that seems rare in USA when I've visited peoples' shops there. I asked one guy for a metric rule and of the 20 or so measuring sticks he had in his shop, there was nothing with metric on (and he was building classicals)!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

I have a 36" graduated straightedge like this http://www.garrettwade.com/product.asp?pn=05S11.01&&SID=W4011000&EID=W4011001&utm_source=Google&utm_medium=ProductAds&utm_campaign=Google1&cvsfa=3928&cvsfe=2&cvsfhu=30355331312e3032&gclid=CO3H6f7Y4bcCFc5DMgodwGkALg
Use it for fret slotting, bridge placing, checking neck angle, flatness of various surfaces, as a knife guide for slicing veneers... it's cheap and it works.

7 inch combination square, which is a square, short ruler, and straightedge all in one.

I also have a 24" flexible steel rule, but I don't use it very often. It does have metric on one side, at least.

I prefer those marked in 64ths. the metric system is not so good for measuring by eye in woodworking. I can see and mark a 64th with accuracy and estimate a 128th pretty well, that's a resolution of .016" accurately and .008" with a plus or minus of.003" or so. Compared to the metric system where 1mm is the finest resolution you can see by eye as the next division would be ten segments within that. So there you can accurately measure .040" and guesstimate at .020" for the half millimeter. I have one rule marked in 100ths but seldom use it.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

Some rules have 0.5 mm graduations, usually for the first section of the rule. You can split that by eye (if you really need to) to get 0.25 mm's.
The only time I can think that I require that kind of accuracy is when making a fretting rule - and I use magnification for that.
Perhaps it's just my age but I find find the very fine markings more of a hindrance. A 1 mm division is perfectly adequate for me. I can guess the rest.
Digital calipers

I've never had a problem using it for building everything from sheds to boats to guitars. I suspect most of the rest of the world hasn't, either, as it's what gets used virtually everywhere but the USA.

I have Toledo brand satin SS rules, 150mm, 300mm, 600mm, 1000mm all graduated full length in 0.5mm increments, eye-ballable to 0.25mm (10 thousandths) on one edge, 1mm on the other. All the accuracy needed for the longer lengths on guitars. (They're also part graduated in 50th and 64th inches on the other side, which I never use). I slot fretboards using CNC'd templates. If more accuracy is required, it's usually on small parts, which is digital calliper country. For measuring out string lengths for intonation purposes I use a precision 600mm brass measuring "stick" and measure out from that for the extra length with digital callipers.

I can relate to that!

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Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

6", 12" and 18" satin chrome flex or rigid rules. metric and imperial
One center ruler, local hardware store.
A couple of wooden 18" steel edge rulers from public school.
one Stumack attack string spaceing rule...highly recommended...especially if you into
building all different sorts of things with strings. Me hates doin the maths.
One surveyors tape...has 10 inches to the foot...
Two wooden and one aluminum yardstick from the 1950's with silk screened numbers...real funkie. Every once in a while me will joint the edge of the aluminum one...Just to have somthin thats somewhat really straight around here.

Lets see...bout a half dozen or so assorted tape measures from the local lumberyard, hardware or Wally Mart .

And finally, about a year or so ago me breakded down and bought some digital calipers. Yes is true.

Truth be knowen me uses the 18 inch and the wooden yard stick the most.

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Audiences and dispensations on Thursdays ~ by appointment only.


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That would be tenths of a foot, not inches. I much prefer tenths of a foot over inches...

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A man hears what he wants to hear, and disreguards the rest. Paul Simon

I accord you your privilege to prefer what thou wilt.

However the correct term for one tenth of a foot on a surveyors measuring tape is still called one inch.

When ever me use to have a smart azz on site, me would hide his tape and say "here use mine" Let them do a few cuts, then say, "hey, theres your tape, give me back mine" Then watch the smart azz try and figure why non of his cut don't fit.

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Audiences and dispensations on Thursdays ~ by appointment only.


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Now that's a concept I can appreciate, imperial metric! Ten inches in a foot, ten tenths in an inch.
Incidentally, that is exactly the system I use in my day job as a civil engineer/surveyor.
I do recall some of the oldtime surveyors using survey inches....

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A man hears what he wants to hear, and disreguards the rest. Paul Simon

Ya Roger...real old timers...like me eh...
Oh ya me forgot....when doing break out me prefer to use a No. 68 Upson or a No. 61 Stanley Same difference.

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Audiences and dispensations on Thursdays ~ by appointment only.


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My rule is to never use a scale that reads over 175 lbs.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker