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2PR & 6PR thread sizes.
- Thread starter RichardB
- Start date
My notes say use a 5/8" x 18 tpi Conduit which is 55 degrees but hard to find. Fits 2Pr vickers & tank & 6Pr 7 cwt & 40mm Bofors. Check before using.
A 5/8" x 18 UNF is 60 degrees and removes some metal from the V in the threads, but still works if you are re-tapping the primer threads to clean them.
The No 281 thread should be left hand but I do not have one to check diameter and threads but should be 55 degree form?
A 5/8" x 18 UNF is 60 degrees and removes some metal from the V in the threads, but still works if you are re-tapping the primer threads to clean them.
The No 281 thread should be left hand but I do not have one to check diameter and threads but should be 55 degree form?
If it is 5/8” x 18 tpi BS Conduit, there are used taps and die currently on eBay in the UK.
www.ebay.co.uk/itm/224773317218
www.ebay.co.uk/itm/205004524200
www.ebay.co.uk/itm/224773317218
www.ebay.co.uk/itm/205004524200
TimG is correct as 6Pr 7cwt is 7/8" x 14 threads Whit and is an odd size. My error in my thread book . Sorry.
The 5/8" x 18 tpi conduit IS correct for 2Pr Vickers, 2Pr tank and 40mm Bofors.
If the threads only need a clean then use a thread file or hand scrape with an 18 or 14 tpi tap of smaller diameter to remove rust. It saves buying a starter of finish tap.
Primers are usually only threaded for 1/2" approx. depth so easily cleaned.
If 6Pr threads are bent or badly damaged then retap with a 7/8 x 14 UNF which will remove metal but the No 15 primer still screws in nicely and nobody notices the thread difference.
The 5/8" x 18 tpi conduit IS correct for 2Pr Vickers, 2Pr tank and 40mm Bofors.
If the threads only need a clean then use a thread file or hand scrape with an 18 or 14 tpi tap of smaller diameter to remove rust. It saves buying a starter of finish tap.
Primers are usually only threaded for 1/2" approx. depth so easily cleaned.
If 6Pr threads are bent or badly damaged then retap with a 7/8 x 14 UNF which will remove metal but the No 15 primer still screws in nicely and nobody notices the thread difference.
As it turns out, the 6PR 7Cwt primer thread is not, 7/8" x 14 TPI, its quite a bit smaller, so i might try the 5/8" 18 TPI.
All is not lost, as the thread of the 95mm case is 7/8" x 14 TPI, and id guess the 17PR is also, although i didnt try.
So ill try to find a 5/8" 18 TPI next.
...As for the 2PR Fuze, I've not been able to find a LH 3/4" 12 TPI tap anywhere.
All is not lost, as the thread of the 95mm case is 7/8" x 14 TPI, and id guess the 17PR is also, although i didnt try.
So ill try to find a 5/8" 18 TPI next.
...As for the 2PR Fuze, I've not been able to find a LH 3/4" 12 TPI tap anywhere.
You must be wrong. The 6pr 7 cwt uses a No 15 Mk 11 primer in all my cases which is 7/8" diameter and 14 threads per inch.
What is the headstamp on your case if it has a smaller diameter primer?
If British just re-tap the threads to 7/8" x 14 UNF and do the primer too. You only change thread angles and nobody could tell the difference.
What is the headstamp on your case if it has a smaller diameter primer?
If British just re-tap the threads to 7/8" x 14 UNF and do the primer too. You only change thread angles and nobody could tell the difference.
I might have one, I have a lot of LH BSF and BSW taps.