I’ve been trying to identify this item which looks like a base plug but of course could be something different. Measures about 1 3/8 inches in diameter, fine threads on the outside, two holes for a spanner, one screw, and a central hole with several smaller holes that lead to the opposite side. I’m assuming it’s ordnance related but maybe it’s part of a large optics or instrument. Recovered from the Courcelette battlefield. Any ideas appreciated.
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Base plug?
- Thread starter Infanteer
- Start date
Eggburt1969
Well-Known Member
Don't quote me on it, but I've had a look at the battles around Courcelette and it doesn't seem American forces were present.
As such it may be a 'British' No. 85 (Number 85) series time and percussion fuze. As far as I can tell, the No. 85 was based on the M1907 series of US combination (powder train time and impact) fuzes.
If it was a No. 85 it would be the assembly labelled as '4' in the diagram below.
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Eggburt1969
Well-Known Member
Hmm, I looked through quite a few sectional diagrams of the No 80 series (Mk. V, VII, XI, plus some of the No. 80/44) and checked what's supposed to be different between the Mk. I to Mk. V models, but none show or mention that sort of base plug? As such, what Mark is that No. 80 fuze?
If not the base plug of a No. 80, could it be that someone has just used one from a No. 85 or M1907 series? I don't have technical drawing with dimensions, so can't check if the base plug thread sizes are compatible.
Alas I don't have that fuze anymore and no more pics, just checked all my other No80s and like you say they are different, so it could be a No85 base
The find shown in the opening post is indeed a base plug for a No.85 fuze...
https://www.bocn.co.uk/threads/unknown-ordnance-item-british-ww1.82368/#post-202856
https://www.bocn.co.uk/threads/unknown-ordnance-item-british-ww1.82368/#post-202856
Yes, it does appear very similar. One difference I can see is that the center of the base plug on the No85 in the drawing and the example on the other thread are hollow, whereas my example is closed with a dome of brass. Without cleaning the mud from the piece, I don’t know if it’s truly different or if there’s a separate piece of brass stuck in there.
Thanks for the help everyone!
Edit: My example is solid in the center like that in the photo of the No80 shared by Andysarmoury. I have several No80 fuzes and none have that version of base plug, so that must be a different variant.
Thanks for the help everyone!
Edit: My example is solid in the center like that in the photo of the No80 shared by Andysarmoury. I have several No80 fuzes and none have that version of base plug, so that must be a different variant.
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Perfect, that settles it. Thank you very much!
Eggburt1969
Well-Known Member
I was going to post in this crudely highlighted version of the diagram, which highlights the shape of the No. 85's (and hence M1907 series') base plug, but was beaten by the better photos.
Anyway, hopefully the highlighted diagram makes it easier to see that the shape of the No. 85's base plug is as per the muddier versions first posted by Infanteer.
The reason Infanteer's muddy original is bulged in the middle is likely due to the pressure that was reached within the brass structure when the black powder charge deflagrated. The pressure was high enough to plastically deform (bulge) the less well supported central area of the plug, which sits below the impact mechanism (which can move once it has armed).
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Thank you, the highlighting of the diagram makes it much more clear. I’m a bit out of practice in interpreting technical drawings. And I agree with your reasoning of why there is a bulge on my example.