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

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In summary, the purpose of two units of mass in the Imperial system—primarily pounds and ounces—is to provide a flexible and practical means of measurement for various applications, from everyday cooking to industrial contexts. The pound serves as the larger unit for measuring heavier items, while the ounce allows for more precise measurements of lighter objects, facilitating convenience and accuracy in trade and personal use.
  • #36
Cost-benefit analysis for adopting the metric system cold turkey probably does not favor the adoption -- in the U.S. A small country like Australia (13M in the 1970s) probably had a lot to gain. It more or less had to change. The U.S. doesn't have to change.

For the average citizen it would be a PITA. For industry it would result in significant cost. The long term benefit? Maybe not as much as people imagine. And the old system wouldn't simply go away in a couple of years.

I had always been a little embarrassed that the U.S. never made the full switch. But now I'm not so sure how important it really is.
 
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  • #37
JT Smith said:
I had always been a little embarrassed that the U.S. never made the full switch. But now I'm not so sure how important it really is.
It just costs a steady drip drip of money and risk by not choosing to get in line.
 
  • #38
JT Smith said:
For the average citizen it would be a PITA. For industry it would result in significant cost. The long term benefit? Maybe not as much as people imagine. And the old system wouldn't simply go away in a couple of years.
Said like a true addict. It will cost votes.

The aim is not to eliminate the old system, but to formalise the new.
The size of the country is irrelevant. Big countries make bigger savings.

The size of the industry is irrelevant. Big industries make bigger savings.
The automotive industry, in the US, left the US behind in the late 1970s.

The significant cost is not in changing, it is in not changing.
 
  • #39
JT Smith said:
For the average citizen it would be a PITA.
It would be no worse than learning to use a smart phone or drive a Zoom connection. There's a very sad rump of reaction against decimal in UK. There are even some politicians who promise to allow imperial units for food sales.
The 'average citizen' is well capable of this stuff when they have no option. It makes me cross (you may have noticed).
 
  • #40
Baluncore said:
Said like a true addict. It will cost votes.

You mean me? I use the metric system every day. But I also think that the old system works just fine for some things. The metric system as a panacea is a kind of groupthink.

I believe that the main reason for the U.S. not changing is about money. If there were money to be made by changing there would be change.
 
  • #41
sophiecentaur said:
. It makes me cross

To me, it's like being upset with those French people. You know, they have a different word for everything.
 
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  • #42
gmax137 said:
To me, it's like being upset with those French people. You know, they have a different word for everything.
Except the French have an interesting language and culture which is worth getting into. Is there anything at all interesting about 17/32"?? :wink:
 
  • #43
sophiecentaur said:
Is there anything at all interesting about 17/32"?
13.5mm is about 17/32"
 
  • #44
sophiecentaur said:
Is there anything at all interesting about 17/32"?? :wink:
Ha ha. I have these in my box, I'm sure I never used them.
20240210_073233_small.jpg


This one I have used.
20240210_073417_small.jpg
 
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  • #46
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  • #47
jack action said:
BSF? Best Spanner Forever?
British Standard Whitworth = BSW, standardised threads at 55°. Later, when metallurgy and machining tolerances improved, there was British Standard Fine = BSF, also 55°. The Whitworth spanners were marked for the size of the thread = the diameter of the bolt. That worked OK when Whitworth was the one and only standard.

60° UNC and UNF threads appeared in the US, then migrated to the UK during WW2. Obviously, the 55° BSW and BSF threads mismatched the 60° UNC and UNF threads. There were also a 60° BSC = British Standard Cycle thread, and (metric) 47.5° BA = British Association (of Engineers) standard threads.

With so many thread standards, a spanner in the UK, (wrench in the US), (key = clé in France), (key = schlüssel in Germany), (key = chiave in Italy), are now all specified Across the Flats = AF.
Some British spanners during the transition were marked with AF, as say 1/2"AF, to distinguish them from 1/2"BSW, or 1/2"BSF, but are now simply marked 1/2".

Standardisation has reduced costs and employment.
The number of inventory items that must be kept in stock as spares will fall gradually as old stock is used or scrapped.

I need a LH 1-1/4" BSF nut to repair an old saw bench. They used to be a commodity, but I could not find one available anywhere. It is not easy to cut left-handed internal threads in an old engine lathe, because the start of the cut cannot be seen.
 
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  • #48
jack action said:
And to complete this discussion:

View attachment 339508

Subway refuses to answer my questions about whether it's an International Footlong or a US Survey Footlong. A milligram of sandwich is at stake!​
good show
 
  • #49
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 ??
 
  • #51
Nik_2213 said:
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.
 
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  • #52
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... )
 
  • #53
Merica!!!!!
 
  • #54
MidgetDwarf said:
Merica!!!!!
I hale from the anagram, Mercia.
 
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  • #55
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).
 
  • #56
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.
 
  • #57
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.
 
  • #58
sophiecentaur said:
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.
 
  • #59
gmax137 said:
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.
 
  • #60
Metrology is the Science of Measurement
Measurement is the language of Science
Measurement is a Universal Language
 
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