What is the purpose of two units of mass in the Imperial system?

[sophiecentaur]

If you hunt around, there are real-neat 'Metrinch' spanners that have a sorta-crinkly jaw that grips both eg 3/8" and 10mm 'Across Flats'. Also, they'll usually grip fixing that was one of those before 'wear, tear & rust'...

Tangential: Any-one ever seen an Octal slide-rule ? Or how to craft such ??

I bought a 1" / metric equivalent a while ago. It cost a lot but it did the job (strong enough and a good fit when the right way round. It's in a box somewhere but I haven't needed it for a long time.

 

[Nik_2213]

My pair of 3/8"-10mm 'Metrinch' spanners came into their own assembling several flat-pack workshop-type trolleys. The many M6 nuts / bolts connecting tray sides to risers were not 'close tolerance', and often rejected my 'proper' 10mm AF spanners & drivers. The wider 'Metrinch' tolerance sufficed. And, usually, cleared enough flash / burr from nuts and bolt-heads for the 10mm tools to then grab and tighten.

( A 10mm nut-driver in budget 3.6 V cordless screw-driver saved me almost an hour per trolley... )

 

[MidgetDwarf]

Merica!!!!!

 

[Baluncore]

Merica!!!!!

I hale from the anagram, Mercia.

 

[chrisbroward]

Bumping this because I found some new info!

Apparently (digging through other forums, and looking at old textbooks from archive.org) -- there actually used to be TWO systems of English units taught in the United States, and Great Britian.

One system used pound as a the force unit (Avoirdupois), and slug was the corresponding unit of mass. One pound-force will accelerate 1 slug to 1 ft/sec^2. On earth, 1 slug will weigh 32.2 lb (Avoirdupois).

System two used the pound as a unit of mass, the corresponding unit of force was the POUNDAL. One poundal will accelerate 1 pound-mass to 1 ft/sec^2. One poundal is the equivalent of 1/32.2 lb (Avoirdupois) or 32.2 pound-mass will weigh 1 lb (Avoirdupois).

 

[gmax137]

Engineering textbooks (US 1960s and 70s) explained all this in the first two pages. It really isn't complicated.
Do you know about kips yet, lol.

 

[sophiecentaur]

This thread should be filed under 'History and Politics'. There's a high proportion of opinions and 'instances' and very little Science.
The reasons for having a range of units in any system is convenience and usage. There's a lot of inertia in the choice and use of terms in Engineering because of the way it has been taught - many vocational courses can present a topic in a very insular way ( no time to go in depth) and the same can be true about apprentisships (loose specifications of course content which can be delivered by non- academic staff). These factors lead to the survival of a loose approach to units.
I don't know the solution to this problem as the alternative costs more money.

 

[gmax137]

I don't know the solution to this problem as the alternative costs more money.

I don't think having several sets of units is a problem. As long as each is well defined and useful to those using it.

If (when) someone makes a mistake in their units, it is because they aren't being careful. It is not the unit's fault.

 

[sophiecentaur]

I don't think having several sets of units is a problem.

It's potentially a massive problem for communication between even clever peoplr. If you never have a problem then you are lucky or very smart.

 

[Ranger Mike]

Metrology is the Science of Measurement
Measurement is the language of Science
Measurement is a Universal Language