Main shaft output nut

[Pete Ashby]

I am looking for help to identify a thread type on the Leyland Retriever main output shaft from the transfer case the thread appears to be 16 TPI @ 55' RH thread OD 31.75mm ( 1  1/4" ) the nut would be a 6 slotted hex @ 52.07 mm ( 2 3/64" ) a/c flats,  15mm total ht including 8mm deep slots.  The parts list is not helpful as it lists the nut but just says "special thread" I'm guessing this would be to fit a 1  1/4" W or 1 3/8" BSF spanner

Any ideas ?

Thanks

Pete

Edited May 8, 2019 by Pete Ashby

[Zero-Five-Two]

1 hour ago, Pete Ashby said:

I am looking for help to identify a thread type on the Leyland Retriever main output shaft from the transfer case the thread appears to be 16 TPI @ 55' RH thread OD 31.75mm ( 1  1/4" ) the nut would be a 6 slotted hex @ 52.07 mm ( 2 3/64" ) a/c flats,  15mm total ht including 8mm deep slots.  The parts list is not helpful as it lists the nut but just says "special thread" I'm guessing this would be to fit a 1  1/4" W or 1 3/8" BSF spanner

Any ideas ?

Thanks

Pete

Odd size that one. BS only use 55' UNF etc is 60', and on a Leyland  you would think BS.  That said, it is far too fine in TPI for BSF or BSP, and Whitworth is way too big. Zeus tables are pretty comphrensive and they don't list anything like it.

[Pete Ashby]

43 minutes ago, Zero-Five-Two said:

Odd size that one. BS only use 55' UNF etc is 60', and on a Leyland  you would think BS.  That said, it is far too fine in TPI for BSF or BSP, and Whitworth is way too big. Zeus tables are pretty comphrensive and they don't list anything like it.

Certainly is an odd size Rob, having failed to find anything like it in my copy of Zeus tables  I turned to my battered copy of the 13th Edition of the Machinery's Handbook (not an easy read at the best of times) the nearest I can come up with is some unusual American thread forms which does not seem very likely and as you note for the common UNF would be 60'.

To be fair I am measuring the pitch only with a set of thread gauges and not by the recommend 3 wire method ( don't go there never did understand this properly) however the 55' 16 TPI gauge seems to be the best fit.

Confused of West Wales.

 

[MB1944]

Could it be Unified extra fine series which is 16TPI but 60 deg.

https://www.gewinde-normen.de/en/16-un-thread.html

Regards

John

[David Herbert]

As it says on the parts list, this is a special thread, invented by Leyland for that particular application. I used to work for Fodens and they invented their own threads for that kind of thing if there was no standard one that seemed right.

Don't mess the nut up !

David

PS,  It couldn't possibly be UNF as that wasn't standardised until the early 50s. Before that the USA used American Standard threads from which UNF and UNC were developed but not all sizes interchange (like 1" UNF is 12tpi vs. 1"AF which is 14tpi).

Edited May 8, 2019 by David Herbert

[MB1944]

A little pedantic I think. The old SAE threads were standardised into the Unified system  in 1949, but that is not to say that this is not the thread in question.

John

[Richard Farrant]

6 minutes ago, MB1944 said:

A little pedantic I think. The old SAE threads were standardised into the Unified system  in 1949, but that is not to say that this is not the thread in question.

John

Leyland was a good old British engineering product, the Retriever would not have had any US type threads in it, only BSF , Whitworth and as in this case a special size thread of similar form to affor mentioned.

the only British built trucks of that period using NF and NC were Bedford as the were controlled by GMC and shared some mechanical components with Chevrolet.

I work all day either British vehicles of 70+ years and BSF is a pleasure to use. 

[Pete Ashby]

56 minutes ago, Richard Farrant said:

Leyland was a good old British engineering product, the Retriever would not have had any US type threads in it, only BSF , Whitworth and as in this case a special size thread of similar form to affor mentioned.

I work all day either British vehicles of 70+ years and BSF is a pleasure to use. 

No new fangled north American thread forms on the Retriever it's mostly BSF of a very high  grade steel and a smaller quantity of Whitworth all bolts have Ley Ltd stamped on the head real quality build.

 Do I take it Richard your money would be on a 55' pitch?  the TPI I'm fairly confident about. 

You can't beat a BSF or Whitworth thread no matter how long it's been sitting around they always come undone with only a little application of heat.

Pete

Edited May 8, 2019 by Pete Ashby
missing apostrophe

[Richard Farrant]

"Do I take it Richard your money would be on a 55' pitch?  the TPI I fairly confident about. 

You can't beat a BSF or Whitworth thread no matter how long it's been sitting around they always come undone with only a little application of heat."

 

Hi Pete,

I feel sure it would be 55 deg thread angle and the machine shop would be using the same cutting toos on all items such as shafts. My guess is the nut is reasonbly narrow and it would not have had enough threads on it using the standard BSF tpi for that diameter. I have come across this 'special' situation before. Like you, I still think BSF is far superior than what was thrust on us from over the Atlantic. In my 53 years in the trade I have had more trouble with NF threads than I ever have with BSF ............... and as for Metric, I have little time or use for it as I try to avoid modern vehicles nowadays.

[Pete Ashby]

Thank you all Chaps for your inputs useful suggestions one and all 

I'll see about getting a blank made up at 16 TPI with a 55' pitch and see how it fits

Pete