1/8 . The measures of SR

[Sisyphos]

Actually not a SR question.
I am from the metric land.
I am shavette user, but frequent on SR forum(s).
It has bothered me the sizes of straight razors I see on SR forums. 5/8, 8/8 etc.
I figured out myself that it measures in 1/8th of an inch. Can anyone from land of imperial measures explain why an inch is split in 8?

 

[rbscebu]

First an inch (25.4mm) is split into halves of an inch (12.7mm). Then each half of an inch is again split in half forming quarters of an inch (6.35mm). Each of those quarters of an inch are yet again split in half to form eighths of and inch (3.175mm).

That is the reason why an inch is split into eight equal parts

 

[Sisyphos]

This makes sense (in some way). Why not stop on 1/4 or 1/16?

I checked from Wikipedia:
'"The English word "inch" (Old English: ynce) was an early borrowing from Latin uncia ("one-twelfth; Roman inch; Roman ounce")."

"An Anglo-Saxon unit of length was the barleycorn. After 1066, 1 inch was equal to 3 barleycorns"

With this knowlidge it would make more sense to split an inch in 12 or in 3 !?

 

[Alum of Potash]

Yes, what he said ^. It' all about dividing things in half, or multiplying things by two, rather than a decimal count between reference points. 1 becomes 2, 2 becomes, 4, 4 becomes 8, 8 becomes 16, 16 becomes 32, and 32 becomes 64. After 64 it becomes tricky: 125, 250, 500, 1000.

I have a similar question in using the decimal system here in France. Why does a "demi" of beer from a keg measure 25 centiliters while a bag of coffee is sold as 250 grams? Why not 25 centigrams? And isn't a true "demi" 50 centiliters, as in demi-liter? Etc. (Actually, I think the "demi" of beer in the metric system is still dependent on imperial measure, 50 centiliters approximating a "pint" and 25 centiliters a "half-pint." Ditto for informal references to a "livre," or 500 grams, and a "demi-livre," or 250 grams, in the marketplace.)

Personally, I find it difficult to measure beyond 1/16" or 1/32" with the naked eye. An eighth of an inch is pretty convenient in comparison and to estimate. Perhaps that's why razors are described that way as a quarter of an inch would be too general or rough a measurement. Also, my understanding is that the measure is from where the razor's spine and edge meet the stone when lying flat. The rest of the spine does not count in the measure, which is why, say, a 5/8 razor from top to bottom measures a little bit more than 5/8".

 

[rbscebu]

Then you have the likes of @Slash McCoy who thinks in millifurlongs (201.168mm). Americans from the southern states are a strange breed.

 

[Legion]

I get more confused when you get Bengalls that say on the box 3/4, when they clearly mean 6/8

How did they get it so wrong??

 

[rbscebu]

I get more confused when you get Bengalls that say on the box 3/4, when they clearly mean 6/8

How did they get it so wrong??

Because there is no unicode number for 6/8 so Thomas Cadman's software automatically converts it to ¾ (U+00BE).

 

[Slash McCoy]

Then you have the likes of @Slash McCoy who thinks in millifurlongs (201.168mm). Americans from the southern states are a strange breed.

Actually we don't use milli-furlongs. 0.1 furlongs = 1 chain. A chain = 4 rods. A perfect acre is 40 rods x 4 rods, so it is a very handy unit of measurement. A bit of trivia for you. Mash your thumb down on a piece of paper and trace the outline. Measure it. It will be very close to one inch wide. You can calibrate your personal inch and never need a ruler again, if you are capable of dividing x 2 and powers of 2 up to say 128. The Ford Model T, the car that put the world on wheels, used tolerances of 1/128" and it was one of the most successful cars ever made in terms of sales and longevity. Plus, a pint of beer tastes better than 50 centiliters. Especially a 20 oz English pint, one very important part of why the US admires the UK in spite of their horrible cuisine. Well, TBF, I am partial to Beef Wellington and Yorkshire Pudding. I'll have about a 20 ounce slice, please, medium rare.

 

[Alum of Potash]

And now back to razors...

 

[cotedupy]

Haha this is a fun q. though I'm afraid the answer is: no really sensible reason.

Imperial measurements have very little coherence because they all evolved separately for different units and in different applications or professions. Many were based on things that people could use easily to measure stuff when precise mathematical instruments were expensive, like your thumb being about an inch as Slash said, or horses getting measured in hands.

The big problem is that they don't have a standard base, even within for example - units of measurement. An inch gets split in 8, but there are 12 inches in a foot, three feet in yard, 220 yards in a furlong, and then back again to 8 furlongs in a mile. I mean honestly!

And that makes doing sums in imperial measurements nigh on impossible, because western numeracy is built on Base 10, the Decimal System. To do calculations in other Bases you need to constantly convert between units, which is a right faff. So ideally you want your all your measurements to be built on the same Base as your numbers are... like the Metric System.

Furthermore many of the units in the Metric System talk to each other. A gram is the mass of 1 cm3 of water at 0 deg c. Which means you can easily calculate and do sums with things like density where the SI unit (mass / volume) involves more than one type of measurment.

The Imperial System is incomparably more stupid and bothersome.

 

[Gamma]

Inches are broken down, sometimes, to 1/64ths or finer, not just 1/8" increments.
I've always felt that differences of 1/8" are easier to differentiate by eye, than say - differences of 1/16". So maybe it's a more useful unit for marketing/retailing/etc.
To my eye, a 6/8 'looks' significantly larger than a 5/8. But a 20mm blade may look nearly identical to it's 19mm cousin.

Sorta reminds of the story behind 'Pieces of Eight' - the coins broken into 8 'bits'.

 

[Slash McCoy]

The Imperial System is incomparably more stupid and bothersome.

For people who can't do math, this is in many ways quite true.

However that does little to cancel out the benefit of having a real world every day baseline for many traditional measurements. For instance, if I know I need a 62' long piece of rope to make a new lifeline on a ship's gangway, I am not going to laboriously measure with a ruler or yardstick or even use a 100' tape measure. I will pull it off the spool fathom by fathom, and having done this before and "calibrated" my personal fathom, I will be within a foot when I mark for cutting. This is just an example. I was at a thrift store once, looking for a set of cognac balloons and I passed by an old man measuring pants. He would fasten the waist button, stick his elbow in, and stretch the doubled waistband along his forearm and note where on the edge of his hand the doubled waistband reached, for his personally bio-calibrated pants size. Just another example. Real world measurements in real life situations are much more relevant than the distance light travels through a vacuum in exactly 1/299792458 seconds. If I want to build a new shed, the process begins by stepping it off in yards and seeing more or less how it fits into the overall lay of the available area for construction.

Custom and tradition count for something, too. I have never heard of anyone asking a clerk in a liquor store for a 750 ml bottle of Wild Turkey. It's still a fifth. When you see a quarter acre lot of land, you know it is a quarter acre and you are not going to torture your brain figuring out how many hectares or how many square meters it is.

 

[StillShaving]

Intuitively I think it must be as previously stated. That going finer was deemed uncessary by most barbers and shavers. Arguably units of 1/16 could be useful at the lower and upper extremes of razor sizes, but it is hard to imagine that going finer (1/32") to be useful. Starts to be too hard to notice a difference.

I like how the same "scale" or terminology is used for clipper guards. I have walked into barbershops in foreign countries, where it was difficult to communicate about the haircut. Where pointing to a plastic electric clipper guards and asking for a number 4 (or whatever is the desired length) for a 4/8" guard made it much easier to get the desired haircut.

 

[StillShaving]

Another personalized calibration that I find very useful, is the distance between end of thumb and end if pinky when fully outstretched. Giving a perfect 9 inches if not stretched too flat. It is a nice and handy ruler with convenient units in that 2x is a 1.5 feet and 4x is a yard. I often use it when out shopping. I imagine most gents hand-spans are roughly close to that and one should calibrate their own personal ruler.

 

[cotedupy]

For people who can't do math, this is in many ways quite true.

However that does little to cancel out the benefit of having a real world every day baseline for many traditional measurements. For instance, if I know I need a 62' long piece of rope to make a new lifeline on a ship's gangway, I am not going to laboriously measure with a ruler or yardstick or even use a 100' tape measure. I will pull it off the spool fathom by fathom, and having done this before and "calibrated" my personal fathom, I will be within a foot when I mark for cutting. This is just an example. I was at a thrift store once, looking for a set of cognac balloons and I passed by an old man measuring pants. He would fasten the waist button, stick his elbow in, and stretch the doubled waistband along his forearm and note where on the edge of his hand the doubled waistband reached, for his personally bio-calibrated pants size. Just another example. Real world measurements in real life situations are much more relevant than the distance light travels through a vacuum in exactly 1/299792458 seconds. If I want to build a new shed, the process begins by stepping it off in yards and seeing more or less how it fits into the overall lay of the available area for construction.

Custom and tradition count for something, too. I have never heard of anyone asking a clerk in a liquor store for a 750 ml bottle of Wild Turkey. It's still a fifth. When you see a quarter acre lot of land, you know it is a quarter acre and you are not going to torture your brain figuring out how many hectares or how many square meters it is.

Some fair points, though I’d certainly say that for any kind of coherent scientific calculations you need your measurments to be in the same Base as your numerical system. It’s a complete mess otherwise.

For more day-to-day things other ways may be more practicable. And as you say for that - much depends on culture and tradition. Here in the UK for example no one would know what a ‘fifth’ or a ‘quart’ is (honesty - what is it a fifth of? I have no idea). We’d ask for a ‘bottle’ or ‘700 mil’ to differentiate it from a litre bottle, or a ‘half bottle’. Though in Ireland you might get a ‘naggin’ which is a 200ml bottle of spirits, and obviously in both countries we still use Imperial pints when ordering in pubs.

Likewise the only time I really use measurements of land is professionally, when talking about vineyard sizes. And we use hectares broken down into ares, not acres.

People in the US still use Imperial measurements a lot more than most other Western countries.

 

[Eastcoast30]

I think someone had already asked this question many moons ago!

 

[VintageGent]

As someone who works with both systems, IMHO the metric system is better for doing math (or, maths) on paper; for things that are not to human scale: micrograms per liter, kilometers to the moon. So it’s good for creatures such as engineers or astrophysicists.

But imperial measurements are better for humans, for describing things the human eye can perceive: the width of a hand, the length of a foot, a hog’s head of ale, the length of a furrow one man with oxen can plow in a day.

If someone says, how big was the snake you saw, you don’t pull out a slide rule and say, “between 17.3267 and 18.4291 decimeters.” You hold up your hands to indicate the space between them and say, “this big!”
Ok, so about 4 feet; big snake.

Metric = good for the classroom or lab
Imperial = good for the field

 

[VintageGent]

*I was speaking tongue in cheek, of course - for the most part. Both systems have their virtues and limitations, and a lot of what makes sense to you depends on which system you were raised with.

But it is true that the various imperial ststems evolved from very, very old roots, starting with agreeable standards drawn from the human body and nature. The metric system was designed by a committee, on paper.

 

[rbscebu]

I still often convert dollars and cents ($.¢) into pounds, shillings and pence (£/s/d). It shocks me what things cost now, £2/12/3 for a pound of butter! My father use to charge his clients in guineas with his clerk receiving the extra shilling.

Having learnt how to add, subtract, multiply and divide £/s/d in primary school gave me a much greater understanding of working in different bases when computer coding was required later in life.

 

[Brutus]

View attachment 1547996

The ingenuity of American engineers in the space program was demonstrated by the fact that they landed on the moon despite the imperial system, not because of it.