UNC/Whitworth - not always interchangeable

[bobc]

Got a flange mount motor from Taiwan with studs on. clearly 1/2" diameter "get some 1/2 UNC nuts" says I.
Wouldn't fit. I thought whitworth only had minor thread form differences to UNC. It does in every size between 1/4" and 1.5"
EXCEPT half inch
bugger - whitworth 12tpi, UNC 13tpi. America WHAT WERE YOU THINKING ???????

 

[DAND214]

Metric?
Not much made now that isn't metric.

Dan

 

[Punx0r]

They're not actually interchangeable anyway Thread form and angle are different. They will fit together but not properly.

 

[Chalo]

I'm not aware of anything still being manufactured with Whitworth threading. That's a legacy standard now, like 27 inch tires or cottered cranks.

 

[amberwolf]

FWIW, various forum members have found that there are assorted Chinese products that have threading and bolt sizes that do not match any "standard"; either they are some sort of internal standard, or they are simply formed incorrectly; it's not known which.

 

[Hillhater]

FWIW, various forum members have found that there are assorted Chinese products that have threading and bolt sizes that do not match any "standard"; either they are some sort of internal standard, or they are simply formed incorrectly; it's not known which.

Ahh ! ..exclusive hand made , custom built, just like antique guns ! :lol:

 

[Punx0r]

Badly formed would be most likely.

I'm not aware of anything still being manufactured with Whitworth threading. That's a legacy standard now, like 27 inch tires or cottered cranks.

It's still crops up on a surprising number of things but not so much in the U.S., I think. You may find it on some camera lens threads, the odd pipe fitting and (apparently) stage lighting suspension bolts. Oh, and the Meccano toys In the UK most pipe threads are based on it (BSP).

I don't think there's much reason to use it other than legacy/backwards-compatibility. It's coarser than a similar sized metric thread, which can be useful, but not that much more than a standard metric coarse.

 

[bobc]

Seems unbelievable that before joseph whitworth introduced it mid 1800s there was no standard for threads, engineers just did whatever they wanted (hence the "antique guns" thing). He did a lot of standardisation and development of engineering drawing and left a huge legacy in Manchester where I was at college (I lived in "Whitworth park" one year). There were several "de facto" thread standards around by his day and his standard drew heavily on them to minimise disruption in migrating to his new standard. He invented the "rounding" on the thread peaks & valleys making things stronger & less prone to fatigue. Bizarrely his nuts & bolts had different angles - I'm sure he had his reasons...

 

[Chalo]

For what it's worth, Italian bicycle thread standards feature the same 55 degree threadform as Whitworth, with an oddball blend of inch thread pitches and metric diameters.