[AT] Supposedly why our old tractors are not metric and a fairly simple tutorial

[John Hall]

Fun fact. Did you know metric pipe threads are actually in inches? They 
are actually 55 deg threadform (British Whitworth) but the pitch is in 
metric. And the real fun part is that the rest of the planet can't even 
decide how to spec them on drawing/print/blueprint. Different countries  
have different designations for the same thing. Off the top of my head, 
I think there are a combined 7 different ways of designating metric pipe 
threads (taper and straight), as opposed to just 2. Now we won't split 
hairs with short projection, dryseal or other specialty threads--lets 
stick to 99.999% of pipe threads.

FWIW, I have 30 years in a machine shop and have continually used both 
english and metric without an issue. Its the rest of the planet that 
makes a big ordeal out of it, we just grab a print and go with it. 
English, German, Japanese--its all the same--until we have to use 
Translate Google to figure out the notes.

One more fun fact. Next time you need some roller bearings for your old 
tractor and start measuring them only to find they aren't exactly 
english, convert them to metric--you might ought to sit down first.

I won't even get into European conduit threads--I've only had to do them 
twice.

John Hall