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Experimental "Smooth" One Piece Mills Grenade 1915

roller63

Well-Known Member
Premium Member
My latest addition to the collection of note. An experimental "Smooth" one piece Mills Grenade patented in 1915. All cast iron/steel construction. Patented by Mills in the Summer of 1915. Patent No. 10515. The centre piece is cast integrally with the body, in an effort to save on manufacturing costs and assembly. Apparently there were two versions made, one in cast iron and one in aluminium. I am told that the patent allows for internal or external segmentation, but this example doesn't appear to have either ?
Most of the parts on my example seem to be No. 5 parts, ie. spring, striker, brass pin, ring, brass filler screw, lever with Reg. No. 616009 I think, not very distinct. The body of the grenade was definitely painted black at some stage, some paint remains. It looks like the det tube is brass.
The base plug is obv not the right one because it is a No 23 Mk 3 but it looks like it has been in the grenade for a very long time. Markings on the base plug are : No 23 III 6 18 M. M.
I was told this was bought in an antique shop in Wales, I have no further info on where or when.
Many thanks to Bonnex for technical information, patent No. etc and permission to use the info here and also the extra pic of another iron one and an aluminium one together.
Tony.SAM_0011.JPGSAM_0012.JPGSAM_0009.JPGSAM_0014.JPGSAM_0013.JPGSAM_0001.JPGSAM_0002.JPGSAM_0003.JPGSAM_0004.JPGSAM_0005.JPGSAM_0006.JPGSAM_0007.JPGSAM_0008.JPGSAM_0010.JPGMills One Piece.jpg
 
Well done Tony. I have seen several of the aluminium type but yours is only the second one I have seen in cast-iron. Mills produced a number of interesting designs which are covered by his patents (Rifle Percussion, Aerial, etc) and these illustrated documents are well worth a collector/custodian's time reading.

Nice base-plug too.
 
A great find there, Tony.

This proposed variant needed some major machining, including drilling of the striker tube through the blank casting (some images attached). Also significant casting skills were needed to make the body - the core, to form the inner cavity for the explosive filling, had to be made in a three section core-box. Then where the core was supported in the mould, three holes remained in the casting, which had to be filled or utilised - one was used as a charge filler hole. In addition to that complexity a second core was required to form the bottom cavity above the base plug, to allow the internal threads to be tapped. It was a manufacturing nightmare.

William Mills conceded this by proposing a simplification of a die cast tube insert for the striker. In detailed costing of materials and labour in July 1915, Mills described this variant as "Mills Improved - Fixed Centre, Die Cast Striker Tube", for which the cost came out as 19.10 pence (the proper old pennies of sd). The costing is shown, but even then the price of the base plug at 2.25 pence is omitted.

Compared to the cost of 22.75 pence of the early transverse cast "Mills No.5 MkI", the theoretical small cost reduction was more than offset by the manufacturing complexity.



Tom.
 

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Superb find - chances of finding one must be 1 in hundreds of millions .

Green with envy!

John
 
Well done Tony. I have seen several of the aluminium type but yours is only the second one I have seen in cast-iron. Mills produced a number of interesting designs which are covered by his patents (Rifle Percussion, Aerial, etc) and these illustrated documents are well worth a collector/custodian's time reading.

Nice base-plug too.

Thanks Norman and thanks again for your help with tech info etc.
 
A great find there, Tony.

This proposed variant needed some major machining, including drilling of the striker tube through the blank casting (some images attached). Also significant casting skills were needed to make the body - the core, to form the inner cavity for the explosive filling, had to be made in a three section core-box. Then where the core was supported in the mould, three holes remained in the casting, which had to be filled or utilised - one was used as a charge filler hole. In addition to that complexity a second core was required to form the bottom cavity above the base plug, to allow the internal threads to be tapped. It was a manufacturing nightmare.

William Mills conceded this by proposing a simplification of a die cast tube insert for the striker. In detailed costing of materials and labour in July 1915, Mills described this variant as "Mills Improved - Fixed Centre, Die Cast Striker Tube", for which the cost came out as 19.10 pence (the proper old pennies of £sd). The costing is shown, but even then the price of the base plug at 2.25 pence is omitted.

Compared to the cost of 22.75 pence of the early transverse cast "Mills No.5 MkI", the theoretical small cost reduction was more than offset by the manufacturing complexity.



Tom.

Thanks Tom, I'm really pleased with it ! Thanks also for your additional technical info as always. It makes interesting reading. As you say this variant must have been a nightmare to make, hence probably the reason it didn't go into production. You can see where the other holes have been filled on the body.
 
Superb find - chances of finding one must be 1 in hundreds of millions .

Green with envy!

John

Thanks John, it's nice to find something like this once in a while. It will take a prominent place in my collection. Don't stay green for too long ! :)
 
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Tony . Here's a pic of one I have . Basically the same as your except it has the curved profile lever & the iron plug is stamped No23 with no mark number & is MMCo & dated 7/16 . The picture on the right shows two with the same body profile but made of aluminium & the bottle shaped one is another Mills variant with only a base plug but also made of alloy . Now we know there's at least two ! Mike.
 
Very interesting Mike ! I think Norman has a cast iron one too, so we can say we know of 3 now ? Thanks for showing it and interesting to see that yours also has a No. 23 baseplug. Does anyone else have one ? Tony.
 
Very interesting Mike ! I think Norman has a cast iron one too, so we can say we know of 3 now ? Thanks for showing it and interesting to see that yours also has a No. 23 baseplug. Does anyone else have one ? Tony.

Once upon a time Tony. I only collect information nowadays. You are back down to two.
 
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