My metal ruler was wrong.

[modeller_masa]

 

I bought several metal rulers (Up) $1 each. I wasn't surr of the accuracy of them, so I tested them with my stock rulers (Down). 

 

Surprisingly, my favorite metal ruler, which has been used for 10 years, was wrong. 🤪

 

 

I examined every rulers I own and discovered that only this old ruler has a different scale...

 

 

I've used it since I was an international student. It was a bit of an awkward truth... I'll check every ruler I buy. 😆

 

[bruce d]

Masa, it happened to me too, but in the workplace. It was an expensive lesson.

Thanks for posting. 

Edited March 7, 2022 by bruce d

[JohnLea]

Is there a definitive way to check a ruler.  What if your favourite is correct and the others off?

[Gregory]

How much precision do you need?

 

Even with the OP example I am having trouble seeing where the error lies as the two examples are shifted.

 

When I take the image and line up the markings, they appear pretty close to me..

 

My altered image.

 

If you have two rulers that are different, how do you know which one is wrong?

Edited March 7, 2022 by Gregory

[starlight]

It could be the case that the "zero" has worn down over time on one of the rulers.

 

If you own calipers I would probably just check the ruler against that, since it will typically be made to higher accuracy than the ruler. You can also buy gauge blocks for a reasonable price. A pair of 1-2-3 blocks is cheap and I've found them to be very useful while modelmaking.

 

-starlight

 

[Dziadeczek]

Masa, you did not align both rulers precisely - hence you have this discrepancy. Go ahead and ALIGN them again. I have a feeling that everything will be OK, judging by your photographs.

[modeller_masa]

Hello, John Lea.

I would say that the digital vernier calipers are the best way to scale models.

 

Gregory. It is a trick of the angle of the camera lens. I just compared every ruler I have, and the old ruler's error was only noticeable.

By the way, I found and know that the 10 years old ruler has a +1mm error at 30cm, and your question led me to examine the new ruler (the above ruler) again. I found an error of -0.2~0.3mm at 30cm. It is barely noticeable, but from now on, I can't resist caring about the error. 😂

[modeller_masa]

Hello, starlight. The Lego blocks are also the best reference gauge blocks under no pressure.  

 

Hello, Dziadeczek. I moved the line of sight vertically both 0cm and 30cm. I'm sorry that the pictures I took may be confusing. I checked rulers manually, and only the old ruler was noticeably wrong. 

 

 

[Oldsalt1950]

When it comes to rulers, yes they will be a little off but within tolerance. However, when you take a measurement, don't start at the bitter end of the ruler. Start at the 1 " or 1 CM mark and take your measurement, then subtract 1 from the reading. The ends are always a bit off.

[modeller_masa]

 

 

I added test results.  

[Diver]

When I went to high school and took shop classes, we were always told that Rulers run countries, and Rules are used for measuring.  I like my Starrett rule.

[Bob Cleek]

9 hours ago, Gregory said:

If you have two rulers that are different, how do you know which one is wrong?

The best way to be sure is to spend the money to purchase rules from one of the recognized quality manufacturers. Accurate rules are intended for use with the desired distances taken up with a pair of good dividers. The divider points make accurate measuring easier as small distances can be seen on the rule's markings. Rules should be handled with care and not used as straightedges, especially not for cutting. 

 

A reliable top of the line brand is Starrett. Their instructional bulletin is a gold mine of knowledge on measuring in the shop:    tools-rules---bulletin-1211.pdf (starrett.com) . They have a separate catalog for rules: Precision Rules, Straight Edges & Parallels (starrett.com) Starrett's competition since forever is Brown and Sharpe. One of their six-inch pocket rules will run you around $23.00 at Walmart, but you'll know it's exactly six inches. Brown & Sharpe 599-313-603 Stainless Steel Stainless Rule, 6" Length - Walmart.com On the used market, another very high quality U.S. rule manufacturer to keep an eye out for is Theodore Alteneder & Sons of Philadelphia, which is no longer in business. Similar names from the past are Keuffel and Esser, Dieitzgen, Post, and Bowen.

 

Modeler's will find triangular architects' scales handy. These have six scales, two on each face of the three sides of the triangular-section rule. The scales permit picking up the scale distance directly from the rule without needing to convert measurements to scale each time you take up a measurement.

 

Top 10 Best Scale Ruler (topportalreview.com)

 

Once upon a time, the manual drafting instrument manufacturers made a wide range of scale rules for architects and engineers. (Another type were  "shrinkage rules" made for patternmakers, whose measurements had to take into account the shrinkage factors of various casting metals.) These rules weren't of the newer triangular pattern, but, rather, each flat rule had two scales, one on each edge. They were beautifully made of boxwood and came in cased sets. There are out there drifting around. If you ever see one for a price you can afford, grab it, because they aren't making these beauties anymore.

 

 

 

 

 

 

 

Edited March 8, 2022 by Bob Cleek

[Jim Lad]

In the end, a minor discrepancy in the accuracy of a ruler doesn't matter at all, so long as you always use the same ruler for your project.

 

John

[Shotlocker]

"One rule to rule them all...one rule to bind them."

[starlight]

30 minutes ago, Diver said:

When I went to high school and took shop classes, we were always told that Rulers run countries, and Rules are used for measuring.  I like my Starrett rule.

 

Having heard this specific admonition as well, I decided to finally look it up. It turns out that "ruler" as a measuring instrument is well attested to in the historical record. 

 

For example this line from the Wycliffe Bible (circa late 14th century): 

"He graueth diligently..bi þe kunnyng of his craft..licne it to an ymage of man, or to sum of beestis; it he comparisowne þurȝdrawinge with a rewler, & make þe colour of it with red & broun."

 

And in Early Modern English, from mathematician Robert Recorde's The pathway to knowledg, containing the first principles of geometrie (1551):

"More easyly..may you fynde and make any suche line with a true ruler, layinge the edge of the ruler to the edge of the circle."

 

As I understand it, both "rule" and "ruler" trace their origin to the Proto-Indo-European "hreg", and then to the Latin "rego", and so forth.

 

All this is my overly pedantic way of suggesting that grumpy shop teachers were simply annoyed that "kids these days" didn't use the same words as they did. 

 

-starlight

[JohnLea]

Good stuff.   I enjoyed the thread.

[Dsmith20639]

I generally use dividers to take or transfer measurements, particularly from plans. I use a digital caliper that reads in fractions of an inch to measure thickness and width of planks. I rarely, if ever, use a ruler for measuring when constructing a model. Also its becoming more difficult for me to read the smallest divisions on a ruler due to my age (77) and gradually failing eyesight.

[Roger Pellett]

An old trick from the pipe fitter trades where wooden folding rules were still used.  Pipe fitters seldom used the first inch of the rule as the end was likely to worn.  No, everything was not built one inch short.😀. They just moved everything over one inch.

 

 

I too like using triangular architect ‘s scale as I like to build directly in scale dimensions.  As this scales have 10 different scales and one regular inch scale,  there is a possibility of measuring with the wrong scale.  To minimize this, a spring paper at least assures that the scale is laid down with the correct side up.

Roger

Edited March 8, 2022 by Roger Pellett

[Bob Cleek]

3 hours ago, Roger Pellett said:

I too like using triangular architect ‘s scale as I like to build directly in scale dimensions.  As this scales have 10 different scales and one regular inch scale,  there is a possibility of measuring with the wrong scale.  To minimize this, a spring paper at least assures that the scale is laid down with the correct side up.

Yes. The triangular "architects'" and "engineers'" rules have grooves cut down the middle of each face. Their purpose was to hold a couple of purpose-designed spring clips that served as grips so the rule could be picked up and set down with the chosen scale always "face up." The spring clips could be set in the grooves so the scale face desired was instantly identifiable. I've only seen pictures of these spring clips in drafting manuals. They're scarce as hen's teeth these days, I suppose, but the grooves remain. As noted, the common spring binder clip serves as well.

 

[modeller_masa]

Argh... I can read replies regarding measurable rulers, but it is hard to read replies regarding unmeasurable ruler literature.

I can't partipate in all replies, but thanks to all for very useful and interesting posts.

Edited March 8, 2022 by modeller_masa

[Dr PR]

This reminds me of when I was a Freshman in college. My room mate was an engineering student, because his father was an engineer (drove a locomotive).

 

I has a cheap dime store plastic ruler, and another more substantial ruler given to me by a friend. The heavier ruler had an inch scale and another in picas (my friend's father was a printer). I noticed that if I lined up the two rulers with the zero marks even there was a difference of about 1/32 inch between the 12 inch marks.

 

I asked my room mate to see his ruler - another cheap plastic one - and it gave an entirely different reading! My room mate insisted that his was the correct one. When I asked how he could know he said it was because his "engineer" father had given it to him. He wasn't the sharpest tool in the box and flunked out after one semester.

 

This experience created a doubt about measurements that is still with me today. In the scientific and engineering work I have done I have always known that EVERY measuring device has some error. And this applies to every measurement of length, volume, weight, concentration and so on. The idea of a perfectly accurate measurement is fantasy. The trick is to know how much error, or how accurate the measuring device is, and take that error into account.

 

Even in CAD programs, where measurements may be given to 15 decimal places or more, there is always a tiny round-off error because computers do not have an infinite number of bits in each memory location. And calculation programs like Excel that can calculate to 30 decimal places are plagued by round-off errors in calculations that cause tiny errors that add up over time.

 

I have several ordinary rulers and yard sticks, seven architect and engineering scales, and three calipers. No two give the exact same measurements, although the more accurate pieces disagree much less than 1%. And of course they change dimensions with temperature changes, so each device doesn't always give the same measurement.

 

And then there is the WAY you make a measurement that can generate additional errors. But that's another complicated topic on its own.

[shipman]

Interesting. I used to work in the print industry. My go to ruler is indeed a UK print industry standard Rabone Chesterman 'Type Scale' which is what I was educated to be conversant.

A very useful instrument. A Pica is 1/6th of an inch. Hot metal compositors relied on these. A Pica consists 12 'points', ie 72 divisions per inch. Commonly  these typescales had 8 and 10 point divisions plus millimeters.  So you get a range of divisions not found on any other ruler.

I've just offered mine next to a couple of cheap plastic rules. Over 140mm (4.5inches) one is ok but the other is .5mm short.                  

[Roger Pellett]

In heavy metal fabricating trades, structural steel, piping, ship fitting, etc.  Work was generally done to a tolerance if 1/8in.

 

In building riveted ships, closer tolerances were required as a 1/8in misalignment in a riveted hole was unacceptable.  In British yards, the practice was to punch holes in one plate erect it on the building ways and then temporarily hang the mating plate, using a paint stick through the punched holes to mark the mating holes.  The mating plate would then have to be taken back to the plate shop to be punched.  An expensive process.

 

In the 1890’s an American shipbuilder named Washington I. Babcock building Great Lakes ships in Chicago, developed a system where all rivet holes, for both mating plates, could be layed out on the mould loft floor.  This system allowed Great Lakes Shipyards at the time to be the most productive in the World.

Edited March 8, 2022 by Roger Pellett

[BETAQDAVE]

5 hours ago, shipman said:

. A Pica is 1/6th of an inch.

That's opposed to using elite and pica typewriters, where elite was 12 characters per inch and pica was 10.  I always thought that 1/6th scale was a peculiar system of measurement to be used for modeling when I had to build my first model of the Wanderer from the A.J. Fisher plans.  I had to make a custom ruler just to build it.  Luckily, they had the fittings kit that matched. 

[Duanelaker]

16 hours ago, Roger Pellett said:

An old trick from the pipe fitter trades where wooden folding rules were still used.  Pipe fitters seldom used the first inch of the rule as the end was likely to worn.  No, everything was not built one inch short.😀. They just moved everything over one inch.

 

 

i have been a union pipe fitter for over 15  years now, and i was actually taught to "cut" an inch by a carpenter.   Alot of people dont realize that the hook end tab at the end of a tape measure can cause errant measurements if you are pushing it against, or pulling it if you are not aware of what you are doing.  I pretty much always measure by "cutting" an inch, gives me much more precise measurements.

 

[shipman]

In typography a font is measured by height not character width.

A Pica is derived from the height of the metal slug that carried a 12 point font (back in the disappeared world of movable type used by printers)

All this is obsolete but the terms are still used today and a type scale is still a useful device.

[Charles Green]

In shops where I have worked no one shared measuring tools of any kind.  Doing so was a sure-fire way to create doubt in anything done on any particular project.  The only thing that mattered was being within tolerance of the inspection gages.  Even the finest calipers were called "guess sticks". 

 

All this being said, Starrett sells a large variety of "rules" (their terminology) graduated in Imperial fractions to 1/64 inch and in decimals to 0.01 inch as well as in 12ths, 24ths, 48ths, and 50ths and 1/2 mm.  They come thick, thin, flexible and in lengths from four to one-hundred-forty-four inches.  Metric rule lengths from 150 to 1800 mm.  With or without hooks.  Any number of them compared will match well beyond the limit of vision.  

[robert952]

Ah, the lengths some people go to when explaining measurements.  😉

 

Sorry, I couldn't resist the pun.  This is a great thread with a lot of information.  Thanks to all for participating.   

 

 

 

 

[Roger Pellett]

British Model Builder Brian King, published a book several years ago describing his modeling techniques.  He specializes in Early 20th Century Warships.  He prefers to use scales graduated in 1/16ths of an inch.  It is his opinion that it is more accurate to interpolate by eyeball between these than to try to pick off 1/32nds or 1/64ths.

[BANYAN]

On 3/8/2022 at 6:12 AM, modeller_masa said:

Hello, John Lea.

I would say that the digital vernier calipers are the best way to scale models.

 

But only if you know the callipers are accurate.  Many of these are not certified as accurate, so which is the more accurate?