American Customary (a.k.a Freedom) Units vs Imperial vs Metric

[jabberwocky]

As a pro architect and hobby woodworker, I prefer imperial units. Aside from just being used to them, base 12 divides in half, thirds and quarters evenly, which are extremely common operations in design at both building and furniture scales. Base 10 divides in half and fifths and thats it. Most materials I deal with are imperial in the US, with some exceptions (like baltic birch plywood is generally metric thickness so what is sold as 1/2" is actually 12mm so a bit thinner).

Aside from that, eh. I'm reasonably good at mentally converting most common units. I model stuff in cad for 3d printing pretty regularly and most 3d printing software is metric so I either have to design in metric or scale it when I go to print. My shop has a full set of wrenches/allen keys in both imperial and metric and I run into both. Most bike hardware is metric. Shop tools are a mix (modern imported tools tend to use metric fasteners, older tools are more commonly imperial, but you find both everywhere).

I just remember that 1in is 25.4mm, 100km is 62 miles, 1kg is 2.2lb and I can mostly work backwards to convert things in my head and be reasonably close when I need to.

 

[jabberwocky]

On last Saturday, my mate Krzysiek was to replace the inner tube in his vintage bike. I wanted to help him with any tools I had with me. No chance! He needed a 15 mm wrench (and it got stuck inside his frame storage). He didn't use Presta valves but Schrader. He had to be self-sufficient!

Way back when I used to commute on a fixie, the cheap bolt on hubs my older bike had used 15mm nuts. Super common on bolt on track hubs in the US and Japan. I kept a shorty 15mm wrench from Sears in my saddlebag as a solution. Eventually put Phil Wood hubs on that bike which used an allen instead (still metric, but a size that most bike multi tools had).

 

[Stefan Mikes]

@jabberwocky: Before the hard times of nowadays, I bought Mirrycle mirrors for several times. As long as the product came from Amazon, all sockets were hex 3 mm despite Mirrycle is an American product. Once, I bought a Mirrycle from a strange seller in Germany. That crook sent me a mirror with imperial sockets! Yes, there was an appropriate hex key in the package. Once that little key was lost... (My brother keeps the mirror, he has got all tools).

 

[jabberwocky]

Bike hardware is almost entirely metric, even in the US. I assume its just because bikes historically were made in Europe so European sizing mostly drove the bus for standards. But there are weird exceptions. Pedal wrenches are generally 9/16". Bike chains are 1/2" pitch. Handlebar clamps are measured in metric but convert to standard imperial (standard 25.4mm is 1in, oversized 31.8mm is 1.25", etc). MTB tires are generally described using imperial (i.e. 2.4" wide) while road/gravel uses metric for widths. I think being a bike mechanic is probably a good way to develop mental flexibility when it comes to units.

 

[Stefan Mikes]

The bicycle was a British invention

 

[spokewrench]

Two normal steps are about a meter, depending on the length of your legs. Unless you are very tall and have very long legs a meter is an uncomfortably long step.

In the US military, a step has been 30" for generations, I believe. A meter is just about 40", so a step is 3/4 meter. Often, a pace is 2 steps, or 5 feet by military specs. The military quicktime cadence 120 steps per second, or 100 yards a minute, or 6000 yards an hour. 18,000 feet/5280 is 3.4 mph, or 5.48 km/h.

A Roman mile was 1,000 paces. It translates to 4860 modern feet, so their paces were abut 58".

 

[spokewrench]

A typical metric car wrench set. The 15 mm bicycle wrench is not here. I also think I needed M18 for the nuts for the hub-drive motor.

I don't think Torx has any relation to Metric or American sizes.

Hmmm... the set skips both 15 and 16mm. They're 12-point rings, so a 16 might have worked on an M15 nut.

It's nice that Torx isn't Metric or American. That way you don't need 2 sets!

 

[spokewrench]

@jabberwocky: Before the hard times of nowadays, I bought Mirrycle mirrors for several times. As long as the product came from Amazon, all sockets were hex 3 mm despite Mirrycle is an American product. Once, I bought a Mirrycle from a strange seller in Germany. That crook sent me a mirror with imperial sockets! Yes, there was an appropriate hex key in the package. Once that little key was lost... (My brother keeps the mirror, he has got all tools).

Within the last year, that happened to me on a new handlebar device. I think it was something where the screw was harder to reach than on a mirror. I think Torx was a worthwhile invention. Fewer sizes, and a fit loose enough to make it easy to connect.

 

[Stefan Mikes]

so a 16 might have worked on an M15 nut.

I don't think so

Regarding different sizes of bicycle parts, many are certainly inherited from English ones. Nobody, however, makes the fuss with, say, 27.2 or 31.8 mm. What is great are the standard hex sizes in cycling! For instance,

Pedal wrenches are generally 9/16"

Yes (we use 15 mm for that) but good pedals can be loosened/tightened with a hex 8 mm key.

As a pro architect and hobby woodworker, I prefer imperial units. Aside from just being used to them, base 12 divides in half, thirds and quarters evenly, which are extremely common operations in design at both building and furniture scales. Base 10 divides in half and fifths and thats it. Most materials I deal with are imperial in the US, with some exceptions (like baltic birch plywood is generally metric thickness so what is sold as 1/2" is actually 12mm so a bit thinner).

My late Dad would have certainly agreed with Jabber regarding the sizes of the U.S. construction material. I could've already mentioned that but he had to add an extra floor to the house of his old acquaintance in America and was charmed how easy everything was!

A question to you. We the Polish have funny names for these adjustable wrenches:

French (Left)
English or Swedish (right)
What are the proper English names for those?

Ya, we Poles have many funny names if you think of it... Allspice is "English Herb" But I digress.

 

[indianajo]

The single reason we havent fully accepted metric is because the French invented it.

Wong. I worked as a transmission mechanic during the changeover, 90's. GM metric threads were totally different than Chrysler threads, which were totally different than Mercedes threads, which were totally different than japanese metric threads. Ford stayed SAE for the time of my employment. So instead of a shop having bins of standard SAE threads, usually coarse, a lost nut had to be ordered from the dealer. A lot of times the ship time was 4 days from Atlanta or NJ. The shop I worked for stopped supplying bolts & nuts entirely. I had a warranty return because I lost a suspension nut into a hole in the A-arm or frame, I used a nut I found, and it fell off under the stress of road impact.
Imperial & SAE threads were totally different in the sixties. Bicycles followed UK practice in the sixties, followed by Chinese metric. There are still 3/8" x 26 tpi axles on rear on some bicycles, which was totally weird. Standard 3/8" thread under SAE was 3/8"x18 or 24 TPI.