Thread question

10 UNF ? 3/16 BSF ? both 32 tpi as opposed to 31.8

Richard

You could look here:

2BA is pretty close. 0.81 pitch instead of 0.8 and 4.7OD

Ah, but is it Imperial? ;-)

Tim

If the British Association ain't Imperial I don't know what is :-)

John

Are you confusing yourself perhaps? The 2BA is close to a 5mm coarse but the

0BA is almost identical to a 6mm coarse other than the thread angle. They both have a 6mm o/d and 1mm pitch.

or 25.4 tpi in old money :)

Thanks, that did it - it's probably 2BA, as the pitch is a little bit more than M5, 31.36 tpi vs 31.8.

Sheeesh! There's a lot of threads about. Found this:

the comments by secondjeremy and Hybrid_From_Hell seem particularly apt.

-- Peter Fairbrother

"By and large at the end of the 1930's the British motor industry was using the BSF (British Standard Fine) thread standard for its fixings. Other parts of industry used BSW (British Standard Whitworth) threads but the head sizes were similar even if they had different size designations and the BSW head sizes had been re-calibrated.

One of the exceptions was Morris engines which used what was essentially a metric thread with BSF head. This is another story.

BSF threads are quite fine and so considered not the best for fixings in soft alloy castings - so its common to find a BSW thread used there.

All was happy until about 1948 when it was universally decided that the UK should standardise on the American Unified threads (UNFine and UNCoarse) The more common is the UNF thread which is finer than BSF and has smaller heads with the head being measured across the flats (AF)

In 1948 the Land Rover hatched and being the latest technology it used BSF threads for most applications.

In the late 50's or early 60's it was decided that the UK should now standardise on the Metric thread system - so the series 2 Land Rover was introduced with Unified (UNF) threads. In fact they seem only to have been applied to the new bits - so you find plenty of BSF threads which were left there to remind mechanics of their youth when they worked with BSF all the time unless they were dealing with a Morris."

John BA has its roots in metric dimensions

eg the pitch = 0.9mm^BA number

4BA pitch =0.6561mm 2BA pitch =0.81mm

Bob

To add a little more confusion, don't forget the thread angles. 60deg for metric and American threads, 55deg for Imperial (BSW and BSF) and

47.5deg for BA. So metric and BA aren't really compatible!

John

To add a little more confusion, don't forget the thread angles. 60deg for metric and American threads, 55deg for Imperial (BSW and BSF) and

47.5deg for BA. So metric and BA aren't really compatible!

John

And then there's the question of root and crest rounding (Whit / BSF) or truncation (American Sellars thread)...

AWEM

Then there is BSK, British Standard Kippers.

John S.

Ah, but you don't have to screw yourself up too tight to eat kippers - yummy.

AWEM

Only used for fin threads though....

Regards, Tony

Or sole use..................

Ah...sole....

Regards, Tony

I don't understand how you can so so flipper about this ?

Sorry you didn't see the joke

John