Why are SAE sockets formatted in fractions?

[RyanY]

A remaining question is why all major brand (and maybe all brands) ratchets and sockets use SAE fractions for the drive, regardless of whether they fit SAE or metric bolts.

I have 1/4, 3/8, 1/2, and 3/4 inch drive ratchets, not 6.35, 9.525, 12.7, and 19.05 mm drive ratchets.

 

[Blueshound]

I'm still trying to complete my fractional set. Anybody know a source for 1/3", 1/5" and 1/7" sockets? (German or Japanese only please. And I only buy knurled chrome). Thanks in advance.

 

[D60]

really boils down to remembering 2 numbers... 254 and 3937 and knowing what to do with them and where to place the decimal..

This. And knowing when to divide or multiply. Sometimes I choose the wrong one but fortunately the results are so outlandish I realize I screwed up immediately

 

[JWC86]

Don't Canadian carpenters use fractional?

While Canada has been technically on the metric system for quite some time most of the commonly used measurements are still in inches and fractional measurements or mixed and matched where one system makes sense or than the other, this is especially true in my industries in Canada.

25.4 gets punched into the calculator Al lot here, iykyk.

 

[JHZR2]

They used to teach fractions in grade school. Probably not anymore, replaced by some more important gobeldy-gook.

I can assure you they do. At least in reasonably good school districts.

 

[hrv]

I dont worry about it... I have a complete set of Metrinch that I purchased in 2005 and they are great...They fit both SAE and metric...They grab the walls of the bolt so even if they are stripped at the edges it still grips great to remove the bolt...

 

[John105]

Probably because it's always the way it's been done. Besides, fractions are simple once you understand them

people can't even understand mpgs today, let alone fractions like 13/16. Can you imagine asking somebody to explain mph?

 

[John105]

Like the snap on (not the brand) length guards on hair clippers. They're 1/8" based (#1 = 1/8, #2 = 2/8, etc).

I never knew that, but talk about dummying it down.

I once dealt with software back in 2000. It had a windows 3.51 appearance, and a UI showing a woman sitting in an office at a desk. Above her was a clock with an input field. I finally called the vendor to ask, does it really make any difference if I say 1/10, 10/100, 100/1000, 679/6790, and the reply was no. the only reason they have instructions to put an actual number in there was that they found the majority of customers do not understand math and they don't understand percentages. To illsutrate, we wanted 10% but were actually putting in huge numbers like 741/7410. 1/10 is much easier.

 

[Trav]

A remaining question is why all major brand (and maybe all brands) ratchets and sockets use SAE fractions for the drive, regardless of whether they fit SAE or metric bolts.

I have 1/4, 3/8, 1/2, and 3/4 inch drive ratchets, not 6.35, 9.525, 12.7, and 19.05 mm drive ratchets.

The same reason spark plugs even in the US and UK were always metric threads with 14mm being the most common, Ford used a lot of 18mm. Bosch invented the spark plug and made it with 18mm and 14mm threads while it was under patent it was fitted to many engines of the day and became a standard. An American invented and patented the ratchet as we know it, the square drive size I assume is a result of the most common used.
Hazet for one also uses metric for ratchet drives.

HiPer fine-tooth reversible ratchet​

Square, solid 12.5 mm (1/2 inch)

Reversible ratchet​

Square, solid 10 mm (3/8 inch)

Reversible ratchet​

Square, solid 6.3 mm (1/4 inch)

 

[MSCH]

This. And knowing when to divide or multiply. Sometimes I choose the wrong one but fortunately the results are so outlandish I realize I screwed up immediately

exactly... its like someone saying how big is a micron.... I say 1/25400 of an inch, or .00003937...

there are those two numbers.. again... and why sometimes it is easier to express things as a fraction than to use the decimal equivalent. LOL.

easier one is converting pound to kilos or vice versa... 110kilos being 220 lbs... you are either doubling the kilos and adding ten percent
or dividing pounds in half and subtracting ten percent..

 

[Trav]

exactly... its like someone saying how big is a micron.... I say 1/25400 of an inch, or .00003937...

there are those two numbers.. again... and why sometimes it is easier to express things as a fraction than to use the decimal equivalent. LOL.

easier one is converting pound to kilos or vice versa... 110kilos being 220 lbs... you are either doubling the kilos and adding ten percent
or dividing pounds in half and subtracting ten percent..

100kg is 220lb kg x 2.2 (2.205)

 

[MSCH]

100kg is 220lb kg x 2.2 (2.205)

yeah, if you want to take it out to a large set of decimals... 100 kilos is 220 lbs is sufficient for most people..

now when they say some one weighs 15 stone, then I am out of my depth..

where id all the colloquial measurement go?
I can still remember my grandma saying we need a peck of tomatoes..
what was a peck. was it 1/2 a bushel?

 

[Hall]

They used to teach fractions in grade school. Probably not anymore

Sounds like something from a Facebook post that is 100% false. I have school-age children.

 

[thastinger]

This is totally one of those sitting on the toilet pondering life questions but it’s stuck in my head.

I recently had to work on a project which required me to buy and use SAE sockets. I really only work on fairly modern cars and motorcycles which are by and large metric so never really used SAE. I noticed when grabbing sockets from the box and bringing them over to the workpiece I struggled initially a little with assessing how much larger a socket was in proportion to another because the denominator was different so lost perception of scale, a quick way to solve this would to use decimals. Why don’t they do that? I’m sure there’s a reason and I know if you work in standard all the time it becomes second nature but always was curious why they never just did decimals vs different fractions it seems like it would be easier to delineate between sockets like metric.

SAE sockets are in fractions because the bolt heads are sized in fractions

 

[Hall]

yeah, if you want to take it out to a large set of decimals... 100 kilos is 220 lbs is sufficient for most people..

I presume you made a typo in your earlier post when you said "110" and "220", otherwise, 2.2 isn't a "large set of decimals".

now when they say some one weighs 15 stone

All of my extended family (cousins, aunts, uncles, etc) are in Northern Ireland and the older ones always referred to people's weight in "stones". I guess they only cared about weights being close 'cause there's almost no accuracy in a "stone" unit !

 

[K-Man]

A stone is 14 pounds. Seems that it's used only in Britain and only when referring to people's weight.

 

[Kira]

1) I remember guys stating that the Canadian plywood they were working with was metric and created problems while building flooring. I never gave it another thought. Any Canadians want to report?

2) Don't ever forget the 1/4-20 accessory hole in the bottoms of the world's cameras. Thanks Kodak.

3) Someone tell me where the 15 ounce box of raisons came from? (been 15 ounces for ever).

4) Fat, flabby Annie was incredibly big, she weight just about 16 stone....then a quack dietician went and put her on a diet now she looks like skin and bone. The Kinks


Re Hall's post (#53): People love to disparage school systems as a general rule.
Embroidery was mandated at my school and I'm not sad to see it go.

 

[K-Man]

I suspect the real reason the US did not convert most things to metric was all the legacy Imperial stuff in use. The industries that benefitted did change to metric. New US vehicles did start the process in the late 1970s. (My 2011 Ranger is metric.) But other industries saw costs to change, not benefits, so those didn't change. Imagine if you needed a plumbing or electrical fitting, or lumber or plywood, and you had to try to match legacy stuff after everything went metric.

Europe essentially was metric all along as industrialization began in the 19th Century. The English–speaking world stuck with Imperial during that era, so it became established in everything.

At this point there is little benefit to changing the American stuff that isn't already metric.

 

[MSCH]

I presume you made a typo in your earlier post when you said "110" and "220", otherwise, 2.2 isn't a "large set of decimals".


All of my extended family (cousins, aunts, uncles, etc) are in Northern Ireland and the older ones always referred to people's weight in "stones". I guess they only cared about weights being close 'cause there's almost no accuracy in a "stone" unit !

I see it now... I sure as hell did a typo on that one... and now it is too late to edit... my apologies.

 

[SHOZ]

SAE sizes are great for those odd metric or rounded fasteners. Rounded metric allen heads can usually have a SAE pounded down into them to save the day. The manual transmission drain plugs on Hyundais is 15/16" though it's nominally a sloppy 24mm.

And I still find some SAE sizes on almost every car or mower I've had even brand new 2023 stuff. usually the 7/32" as found on the new John Deere muffler shield, the seat bolts are still SAE threads and heads though that is probably for backward compatibility.