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

[Thomas Martin]

> On 25 February 2020 at 15:17 John Hall <jtchall at nc.rr.com> wrote:
> 
> 
> 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
> 
Well, John
Europe did adopt BSP (British Standard Pipe) threads
back in the 19th century, difficult to change horses now.
Quite a simple setup compared to the American system!
Did you know that the US has 11 diffent derivatives of
National Pipe threads? 
As for 11-1/2 tpi NPT, I bet many a lathe manufacturer
swore when Norton invented the quick change gearbox for
lathes and provision had to be made for that.
In fact would say I have cut more peculiar threads of US
origin that elsewhere.
That goes for bearings also. Both Caterpillar and IH used to 
get bearings, especially taper-roller, ground to  their
specific sizes, so that only they could supply, at a cost 
5 to 10 times the cost of a standard size! Extortionate!
Competition finally forced them into standardization in the finish.
FMC was another who engaged in the practice in another field.

Tom