So Here We Go.... Rules Or Scales

[rfdes]

I have seen alot of mixed information regarding this on the internet. I'm professionally an electronics engineer and I've always understood that a rule measures absolute lengths while a scale is used for 'scaling' purposes. Being a beginning hobby machinist, I keep hearing many machinists scolding others to always use the term 'machinist scale' as opposed to 'machinist rule'.

I guess it really doesn't matter one bit but I would like to know WHY it is referred to as a scale as opposed to rule?
Jim
Largo, Fl.

 

[RJSakowski]

I have seen alot of mixed information regarding this on the internet. I'm professionally an electronics engineer and I've always understood that a rule measures absolute lengths while a scale is used for 'scaling' purposes. Being a beginning hobby machinist, I keep hearing many machinists scolding others to always use the term 'machinist scale' as opposed to 'machinist rule'.

I guess it really doesn't matter one bit but I would like to know WHY it is referred to as a scale as opposed to rule?
Jim
Largo, Fl.

Back in the sixties in high school drafting class we used scales. If we referred to them as rule or rulers, we would get our knuckles rapped with one. We also got our knuckles rapped if we used them as a straight edge. Your explanation of the differentiation is very plausible. Perhaps the old timers use the scale terminology because in those days, machinists got their prints from the draftsmen and the draftsmen only used scales.

Haven't seen any tape scales lately!

Bob

 

[Franko]

As far as I've seen there are two types of scales. Architect's scales in fractions and Engineer's scales in decimals, used for drawing scale drawings and plans.

As far as I know, and I've used rules and scales all my life, rules are for measuring length. Persnickety machinists need to lighten up and quit scolding people for silly stuff.

 

[Tony Wells]

I am guessing here, but I think the term scale comes from the old days when mold makers used "shrink rules", which are used to scale up patterns to allow for shrinkage in the casting process. You can google for Starrett shrink rule and get more information. They are available in different ratios, or scales, according to need.

In these parts, most machinists call them scales in general use. That's what I always heard, so that's what my habit is. I don't go around scolding people if they call them rules though. That is what Starrett calls them, and I figure they know a little about them.

There are also things called "Steel Rule Dies" which use what originally may have been someones flex-scale. But it was known as a rule at the time, hence the name. It's a useful thing to know how to make. There are prepared strips used in their making now.

 

[Bill Gruby]

Call me "Persnickety" if you must, but when someone enters my shop, on the door are the rules. Number six states you measure with a scale. Number seven says, "The above is in English no metric".

"Billy G"

 

[dracozny]

The only obscure difference I could find ~ "Machinist's rule: A multiple scale ruler used to measure distances or components that do not require precise measurement." So based on that I suppose we are trying to say a rule is less accurate than a scale. yet every dictionary I have says they are synonyms in this regard. If we are drawing on paper use what you got. the dimensions are often written down anyways. On the work use the appropriate tool for the job, often a Caliper for low tolerance and a micrometer for tighter tolerances.

 

[MozamPete]

Back when I was a draughtsman, in the pre CAD days when we use ink and polyester sheets, a scale was a ruler the was was at other than 1:1. If you had a drawing of a component that say had a detail drawn at twice life size (2:1) and you wanted to measure off the drawing you would use a 2:1 scale so you would be able to directly read the required dimension. You would never use a scale to measure anything in the "real" world. The real would is at 1:1 so you would use a ruler (or tape measure).

 

[RJSakowski]

The only obscure difference I could find ~ "Machinist's rule: A multiple scale ruler used to measure distances or components that do not require precise measurement." So based on that I suppose we are trying to say a rule is less accurate than a scale. yet every dictionary I have says they are synonyms in this regard. If we are drawing on paper use what you got. the dimensions are often written down anyways. On the work use the appropriate tool for the job, often a Caliper for low tolerance and a micrometer for tighter tolerances.

The reference to scale in your quote refers to the different sets of divisions found on a machinists rule (1/8, 1/6, 1/50, etc.). As Peter said, a drafting scale is typically a three sided device with six different scales on it. The scaling would be 1:1, 2:1, 10:1 so the draftsman didn't have to do any math to correctly draw. I don't know specifically about the accuracy of a draftsman's scale but they were made of wood and there use was to make a reasonable facsimile of the required part so there was not a requirement for accuracy. A machinists rule is usually made of stainless steel and is used to lay out machining work where there is a need for accuracy. If I need accuracy, I would use the machinist's rule.
Actually I haven't picked up a draftsman's scale in many decades even though I still have several.

 

[uncle harry]

The reference to scale in your quote refers to the different sets of divisions found on a machinists rule (1/8, 1/6, 1/50, etc.). As Peter said, a drafting scale is typically a three sided device with six different scales on it. The scaling would be 1:1, 2:1, 10:1 so the draftsman didn't have to do any math to correctly draw. I don't know specifically about the accuracy of a draftsman's scale but they were made of wood and there use was to make a reasonable facsimile of the required part so there was not a requirement for accuracy. A machinists rule is usually made of stainless steel and is used to lay out machining work where there is a need for accuracy. If I need accuracy, I would use the machinist's rule.
Actually I haven't picked up a draftsman's scale in many decades even though I still have several.

I also fondly remember the pre-CAD drafting days & scales. Often a notation was made on a drawing "Do Not Scale" thus drawings weren't considered highly precise. (An exception would be polyester layouts done with higher quality drawing machines for layout verification). Another notation often used was Not to Scale abbreviated as NTS. More often than not it implied "Not too sure"!

 

[randyc]

By "polyester" I suppose that "mylar" is meant. Mylar became the standard for drawing stability rather than vellum paper, at least for the larger drawings that were produced at the Westinghouse Marine Division and other aerospace/defense companies where I was employed.

There was also a coated woven linen fiber medium that was very sturdy and superior to mylar for heat resistance but the coating could quickly be abraded away, especially with the electric erasers that became universal in the 'sixties. I recall that by the late 'sixties, linen was being phased out.

Linen media, as I recall, was used primarily for inked drawings while mylar could be used for both ink and pencil. The mylar drawing surface had a "tooth" - a roughened surface - so that graphite pencil lead would slightly abrade and imbed the particles that then constituted the drawing lines.

Linen media required that the surface first be treated using a fine powder called "Pounce" before inking. The pounce slightly roughened the smooth coating on the linen so that it absorbed the ink. (Without pounce, the inked lines would tend to "bead up" so continuous lines couldn't be produced.)

Old-timers may recall drafting pencil lead hardness classifications: for example, 5H was often used for construction lines, 4H for center lines and dimension lines and 2H for object lines and H for lettering. There was also a product consisting of fine particles of rubber erasing compound contained in a cloth bag but I don't recall what we called it.

The bag was coarsely woven so that the particles could be released as the bag was squeezed and manipulated over the drawing. The resulting fine particles were then lightly brushed over the surface of the pencil drawing with a drafting brush (another tool that has disappeared with the usage of CAD). The purpose was to absorb the fine dusting of pencil graphite that inevitably spread over the drawing surface, to keep the drawing cleaner.

Man, does this thread bring back memories. Here are a few manual drafting tools that I still own and sometimes even use, LOL. There are also two Dietzgen compasses and a pair of dividers out in the shop that find occasional use. In the center of this photo is a triangular architects scale. This one is special because it was first used by my Dad then passed on to me. The scale is approximately ninety years old.