Classic cars forum & vehicle restoration.

[admin]

Would someone mind clarifying who/what/where/when various different threads apply to vehicles?? ie who used UNC, BSF etc?

ta
Rick

[buzzy bee]

I would love to know this too, I have loads of taps and dyes and dyenuts in alsorts of sizes and threads. What do the letters stand for, I know some, like unc, unf but what about bsf, bsp etc

[Uncle Joe]

I'll have a shot at this, using some of the old British Standards that I have, but due to there being so much information, can you all ask some specific questions?

I've seen Buzzy's question about what the letters mean, so:

UNC: Unified Coarse. UNF: Unified Fine. BSW: British Standard Whitworth. BSF: British Standard Fine. BSTP: British Standard Taper Pipe. BA: British Association. BSC: British Standard Cycle. SI: Metric (note that there are several metric standards - foreigners can never make their minds up)

Some people also shorten British Standard Conduit threads to BSC, but these are nothing to do with the other BSC, they are Whitworth threads.

Now then, does anyone have any comments, and have I left any out?

UJ

[admin]

The idea of posting this question was to get a summary in one place of the popular threads, and where you're most likely to come across them, say on American cars, or British stuff, or what period of vehicles they usually turn up on .. just a condensed quick reference if you like! I pick up the odd nugget of info along the way here and there, but a quick summary would be handy.

ta, Rick

[UKdave2002]

Per war Rolls Royce engines used to have thier own unique threads ! suppose nothing else would was good enough!

[Uncle Joe]

Rick, the trouble is, there is no hard-and-fast rule. Probably the most common threads that you will find are UNF/UNC. Generally, you will find these on all American, and most British cars. But, there can be a mix. One thing that struck me when Buzzy asked about the preload on his E83W was if the nut was for example BSF or UNF.

BA threads will usually be found on British electrical components.

Some cars eg Volvo, may have a mix of Metric and Unified. Then again, just to prove that the Metric system is c**p, an M5 nut off a 1955 VW may not fit an M5 bolt off a 1955 Citroen.

Its all something that you just have to learn.

Any other comments anyone?

[UKdave2002]

From my humble experience (mainly BMC cars) if it was designed before the war then generally BSW, designed post war up to the 70’s UNC/UNF, post 70’s some metric, 80’s onwards all metric.

The other thing people get confused with is spanner sizes and thread sizes, UNF spanner sizes are “AF” across flats width, where as I think Whitworth spanner sizes refer to the diameter of the bolt not the head, so a 9/16 UNF spanner is much smaller that a 9/16 BSW spanner.

Did the Mini retain its UNC/UNF threads right up to 1999? You used to be able to dismantle 95% of a mini with just 7/16, ½ & 9/16 AF spanners !

[Uncle Joe]

UK, I would have a tendency to agree with you as regards rough dates for the changeover from British to American.

The vehicles that I have been wondering about though are Fords. They were quite late on the British scene really, and I cant remember if they have always had UNC/UNF, or AN as its sometimes called.

Rick, maybe you can shed some light on this from your E83W experiences.

UJ

[UKdave2002]

Morris side valve engines have metric threads with BSF/BSW bolt heads!!!
This due to Morris using Hotchkiss engines (French I think)in the 1920's and then buying them out in 1923. I wonder how many damaged threads as a result of people not being aware of this.

[Uncle Joe]

That information is something new to me. I'd like to bet though that no-one who has missed the fact will admit to it!