1st Day 18Pr ~

[Gspragge]

It was a sad day in the plant ~ I was conflicted wether to purchase this or not?
Clearly a poor investment - yet interesting in a cruel way (either to my wallet or some past unfortunate lad :tinysmile_cry_t4
Okay I clearly dramatise, it wasn't that bad --

What is the opinion of the assembled Peers ?

 

[starshell]

Could it have been an apprentice piece, practising machine skills?? Mind you, in the urgency of war, would they have employed apprentices? Or someone just accidently over doing the cutting tool adjustment...
Very interesting piece either way.
Cheers!

 

[2pounder]

from personal experience as an apprentice, a setter set the machine and tools and all one had to do is work the levers. could be a setting fault, loose tool not clamped properly, I've done that on my lathe.

 

[Gspragge]

There must have been lots of apprentices early on with the rapid expansion of the shops making these. This may inpart account for the many more 1915 dated
lamps and such things compared to later year dated "rejects" that one finds. I'm sure as explained there could be a lot of ways this could happen.
While an accident and not made as a teaching aid - though it could have been used as such in the shop - If you don't pay attention this happens and you'l be "docked" ~
At any rate some one took it home - Hey look my first one:tinysmile_fatgrin_t ~ we'll never know.

 

[Alpini]

Could be also a problem with the cast or forged blank which had a too small diameter for machining near the ogive. With sharp pictures it may be visible if that's the case.

The outer shape of the shells were copy-turned. So the setter couldn't have done anything wrong which led to such a failure.

I guess it was rejected prior to attaching the driving band. Is the mouth still threaded?

 

[Darkman]

Does the brass cap screw in? Is there a pusher plate inside? According to a book I have on early shrapnel shell manufacture (1915), the shell body sides were initially turned straight or parallel. Then after the pusher plate was inserted, the body was reheated and forged again to cone over the mouth. The shell was then finally turned in a lathe to neaten the ogive and cut the fuze socket adapter thread.

 

[Gspragge]

Here are more images. The top is threaded for the adapter and the push plate is trapped inside as desribed above.
I wieghed it against a comparable projectile. The only thing keeping accuracy from being closer was the band on one,
if I had a loose band to add to the one without a truer weight difference would have been perhaps found.
As it is they both weighed in at 8 pounds 5 ounces each ~ So I learned nothing ~ :tinysmile_hmm_t:
At what point was the adapter machined to it's final shape, was it in place on the projectile for this operation as it seems
to appear here ?

The unfinished adapter weighed in at 11 1/2 Oz. A finished one at 9 1/2 Oz. So the reject is 2 ounces over standard weight on the adapter side of things. If someone has a weight for the band itself then we can do some subtractions from both projectiles and get
a decent weight comparison. At this point 2 ounces come off the reject to equal the finished projectile, if we can deduct the weight of the band from the finished one then we have it ~

I have added two pages, one giving a finished weight which is much lower than the weights I'm getting. I checked my scale with a 12Pr practice shot which came in at 12 1/2 pounds and a 3Pr practice which came in at 3 1/4 pounds. So I'm not sure how to read a finished shell - is this the empty forged body ?

Aside from nearly cutting the top off of the projectile , the accident brought the body under the minimium diameter limit at the point of damage. Minimum Dia. is 3.28" cut = just under 3 1/4" = 3.24". This of course can not be reversed so rejection was the only action to take. Ironically the inspecter or machinist enitials on the base are "IQ". D'oH :banghead:

I steel wooled all the loose surface rust off of it and it looks cleaner and a little more like the day it was born, I'll just give it a coat of wax and it should be good for years now.

Some one posted a visual description showing the steps of 18pr manufacture, in particular the prior insertion of the push plate, this was quite a while ago.
If you have this can you repost it, I have it but can't find it of course. Maybe explains when the adapter was machined to shape as well ?

 

[TimG]

The machining sequence comes from the 'Process Manual' from the Ministry of Munitions. It shows that the profile is completed prior to the driving band recess being cut. However, these manuals were for guidance more than 'thou shalt.'

TimG
View attachment 18lbsh.pdf

 

[Gspragge]

Are there more drawings in this sequence ?

 

[Gspragge]

Related to this post is a Lathe tool or fitting I picked up today.
It screws into the threaded end of the projectile to centre it on a lathe for
final machining to spec, maybe something like this was in use when my first day
example went pear shaped ? hing like this don't seem to hav esurvived.

 

[Gspragge]

So much for my spelling and typing abilities ~
However I found this image taken moments before things went wrong -
I would think that the above tool was in use, but it's not close enough to show it,
white arrow to where the tool ought to be.
So which one of you dated her ? :xd: