Re: Sanity check- is the TM500 interface spacing .150" or .156"?

Chuck Harris

Fractional inches figures so heavily in so much of older US
engineering, that I am sure that it was really 5/32".

0.156" is simply 5/32" to 3 significant figures.

A milling machine from the era when these connectors were
designed would find it impossible to reliably cut the 0.00025"
residue between a 3 sig figs approximation, and the 5/32"
actual length.

That is why tolerances exist on all engineering drawings.

Your apocryphal British engineer is full of stuff. Given
enough time and money, anyone could cut that residual
difference, but to do so, with real world machines from the
era when Briton still tried to make motorcycles, would be a
waste of that money.

-Chuck Harris

Albert Otten wrote:

I once assumed that a clutch roller length, specified as 0.236" (5.9944 mm), was 6 mm. Totally wrong! This was the reprimand by a respected British motorcycle technician:
--- If a british engineer "aimed at" 1/4" x 0.236" then that is what he got.
If he wanted 6mm he "aimed at" 6mm and got 6mm
to think that they wanted 6mm instead of 0.236 is totally bizarre logic. ---

Tek mentions pitch 0.156" in the TM502A manual. However, I must say that 5/32" is better consistent with measured pitch of plugin edge connectors. I don't know how much the pitch might be affected by humidity or age.


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