who has gone metric?

12bolts said:
I have seen this written before, and it fails to explain to me how you can choose an arbitary number to convert mm to inches. I know its not much, but when you are already working to tolerances of less than 0.0001" commonly nowadays, how do you machine to such a broad tolerance?

Cheers Phil
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Actually, it's not really an arbritrayry number. It is just the ratio of the length of someones foot to the circuference of the earth on the meridian going through paris :)
Here is the Wikipedia entry on it:
http://en.wikipedia.org/wiki/Inch#Modern_standardisation

If it makes you feel better, the ratio is 25.4000000000000000000 :)
 
I learned with fractions and all of my metal working machines are inch machines. But with cars, motorcycles and ATMs they are all metric or a mix of both. I don't see the fraction system going away.
 
The metric system is clearly a cleaner, less confusing system to use as it's a base 10 system. With that said, I still use inches/Imperial when given the choice. Why? Because most of that around me is as such. Lumber is 2x4, 2x6 etc and sheeting is in 4' x 8' sheets. Insulation is manufactured accordingly to fit those sizes, etc. Plumbing is fractionally sized, conduit is inches & electrical wire is AWG (American Wire Gauge) rather than mm squared (mm2). My metric threaded car still uses 14" wheels/tires. on & on...
I work for a manufacturer of hydraulic components. It would be cost prohibitive to build an actual metric hydraulic cylinder in the US, due to the unavailability of metric sized tubing, seals and components. Yes it's available, but here it's gonna cost ya! And why? Because our industry is tooled for inch/imperial sizes, and it would be a great financial cost to convert! (And we all know who pays in the end, right?)
So it goes much farther than that caliper in my drawer, or knowing the ratio of 25.4/1. Until industry as a whole converts to using metric not much is going to change.:leaving:
 
Rods, leagues, inch, foot. All not exactly standard, but based on a measure of the human body, or how far a group of soldiers could walk in a day. Metric does not have that connection.


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12bolts said:
We have had the metric system here is Australia since 1974. I was 11 when they changed over. I still use both systems even now. My children know the basic imperial units and can convert some of them readily.

As honorable as this isyou will still need to use imperial measurements, parts and fittings. If you need to change out 1 stud in a part that has 20 more fractional threads, are you going to have 1 odd fastener, put a frational part back in, or will you change them all? On machinery that has imperial connections, (hydraulic line fer instance) are you going to fit 1 odd connection?


I have seen this written before, and it fails to explain to me how you can choose an arbitary number to convert mm to inches. I know its not much, but when you are already working to tolerances of less than 0.0001" commonly nowadays, how do you machine to such a broad tolerance?

Cheers Phil
Click to expand...

The US inch was defined as 1/39.37 meter (25.4000508mm) in 1866 and redefined as 25.4mm in 1959. The first definition is stll used for the survey inch: the difference is 2 ppm, or about 1/8" per mile.
 
Tell ya this; customer, come in with a broken metric bolt of 334938483 mm. which comes out to 3/8 thats what he gets. Never had in
school its stupid good thing is when a 1/2 rounded nut you bang on a 14mm. so .500 or 1/2 inch its easy than-- 14mm (.5 vs 14)
one half of anything is a half of it so why get all involved with carying a not book. I have some but I only got two in my head like
14mm is a 1/2, 10mm is 7/16 thats it..

1955 we were indroduced to the dewey decimal system in school, Oh boy- we learned it mastered it so it stays. showin my age yep

bottom line is, if you need this across the pond stuff dont come here...
 
GK1918 said:
Hogshead???? that is fractions period. circa 1920's Ford hogshead transmission cover
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I seem to remember that a hogshead is some type of barrel or keg for liquid measure. How Grampa Simpson knew this ?...probably from being stationed in the UK in WWII.
 
GK1918 said:
Never had in
school its stupid good thing is when a 1/2 rounded nut you bang on a 14mm. so .500 or 1/2 inch its easy than-- 14mm (.5 vs 14)
one half of anything is a half of it so why get all involved with carying a not book. I have some but I only got two in my head like
14mm is a 1/2, 10mm is 7/16 thats it..
Click to expand...

Actually....for a 1/2" bolt you would use 13mm & for 7/16" you would use 12mm unless your 11mm is worn enough to fit. :p
 
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