IS THIS AN UNUSUAL No. 17 PLUG?

[Depotman]

I’ve seen quite a lot of No. 17 Plugs over the years, but never one like this, where a ‘band’ of the thread has been machined off. This has resulted in the plug having two, separate narrow lengths of thread. The stampings are as follows:

“No 17IM . GY . SH&S . 1942”

There is also a “Pb” over a “crows foot” and an inspector’s number of “A15”.

Can anyone throw any light on this item? Depotman

 

[TimG]

No. 17 I M - No 17 plug, Mark 1, M - Metal (Brass)
GY - Non lead free, not to be used on shells filled Picric Acid or Shellite.
S.H. & S. - SH&S - Samuel Heath & Sons Co., Ltd. Cobden Works, Leopold Street, Birmingham
1942 - Year of manufacture.
Pb over Broad Arrow - Pb is the chemical symbol for Lead, so I suspect it is something to do with its non lead free status.

I suspect at sometime the threads have been badly damaged and they've been removed (post service) so it will still screw into a projectile.

TimG

 

[Snufkin]

The Pb/broad arrow stamp was the gun ammuntion Lead Free Stamp, denoting less than .1% content lead, or such discretionary limit as approved.

As an alternative to Tim's suggestion - the threads may have been removed to allow the fitting of an O-ring for some reason unknown (pure speculation though).

 

[Depotman]

No. 17 I M - No 17 plug, Mark 1, M - Metal (Brass)
GY - Non lead free, not to be used on shells filled Picric Acid or Shellite.
S.H. & S. - SH&S - Samuel Heath & Sons Co., Ltd. Cobden Works, Leopold Street, Birmingham
1942 - Year of manufacture.
Pb over Broad Arrow - Pb is the chemical symbol for Lead, so I suspect it is something to do with its non lead free status.

I suspect at sometime the threads have been badly damaged and they've been removed (post service) so it will still screw into a projectile.

TimG

Thanks Tim, I'm not sure about damaged threads; the plug has been 'coated', and why bother to coat or re-coat a damaged plug? And why coat a brass plug anyway?

 

[Depotman]

The Pb/broad arrow stamp was the gun ammuntion Lead Free Stamp, denoting less than .1% content lead, or such discretionary limit as approved.

As an alternative to Tim's suggestion - the threads may have been removed to allow the fitting of an O-ring for some reason unknown (pure speculation though).

Thanks Snuffkin, perhaps a reasonable reason to coat or re-coat the plug? Not really a groove for a plug though.

 

[AMMOTECHXT]

I think the threads have been damaged as Tim suggests. Look especially at the lower threads and see the diagonal marks. I have seen such marks before and those were on No 221 fuzes that were difficult to remove from shell due to particulates (sand / rust) that were in the threads. The brass appears to be lacquered, presumably to prevent corrosion that might otherwise hinder insertion or removal of the plug.

 

[Alpini]

The lower two threads look like roughened with something like such a tool: https://rothenberger.com/rs-en/threading-accessories/threaded-roughing-pliers-from-3-8-to-2-56500.

So the groove may really be for a hemp sealing.

 

[Burney Davis]

The machining of the thread (or lack thereof) is deliberate, not as a result of damage. I have seen a number of different plugs machined in the same way. I have added another type of plug taken from a WW2 12pr 12cwt drill projectile. I can't offer an explanation as to why, but Alpini's suggestion that it could be for a sealing ring would seem plausable. Similar comment noted from Snufkin.