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

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.

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.

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.

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).

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.

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.

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"??

sophiecentaur said:

Is there anything at all interesting about 17/32"?

13.5mm is about 17/32"

sophiecentaur said:

Is there anything at all interesting about 17/32"??

Ha ha. I have these in my box, I'm sure I never used them.


This one I have used.

gmax137 said:

Ha ha. I have these in my box, I'm sure I never used them.
View attachment 340101

This one I have used.
View attachment 340102

BSF? Best Spanner Forever?

https://en.wikipedia.org/wiki/British_Standard_Whitworth

More than most people ever wanted to know. Although Whitworth threads are long out of fashion, Mr. Whitworth is the guy who really led the charge on standardizing thread forms.

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.