No5 Mills Grenade Centre Tube Thoughts

[siegfreid]

I'm often asked for No5 centre tubes by collectors & quite often they end up not fitting the grenade they were intended for . Usually this is due to the fact that they won't screw all the way in . The reason for this is the MASSIVE differences in casting tolerances . If you look at the pictures I've included , you can see the top of the det. tubes can be as much as 4mm lower on some compared with others & the slope of the end is much more pronounced . This means they foul the inside of the body before they screw all the way in . Some also have more threads than others . The difference on brass tubes is even more pronounced . I know some early grenades did n't have the internal recess at the top for the tube to fit into but I don't think that explains all the problems . I can only assume the tubes were made to fit the individual casting runs by the hundreds of different makers & were never meant to be interchangeable in the first place . This problem never occurs with No36's as all parts seem to be interchangeable irrespective of manufacturer .
I know Tom has been doing a lot of research on WW1 Mills & , perhaps , he could shine a light on the subject .
I hope this is of some interest to all those avid Mills collectors out there !

 

[Nismosonic]

I have 3 No5 Grens and an early 23, ive noticed that all of the bodies are slightly different in form and shape also. Im sure this would have a bearing on the dimensions of the internals. seems to become more standardised by the arival of the 23MkIII and the 36.

 

[Snufkin]

Mike,

A great display of the variation on No.5 centre pieces.

As is often seen, No.5 (and thereby 23 MksI and II) castings can vary significantly in shape, so the cavity inside the crown varies accordingly. The aluminium centre pieces do appear to have been made for the corresponding casting runs, and although dimensions were specified on the engineering drawings, it corresponds that the form would be tweaked to match the internal space of the grenade bodies.

The key external dimension of the centre piece was its height (2.71 to 2.73 inch), and as long as there were three threads available in the mouth of the grenade to hold the base plug, and the inspection gauges fitted, that part of the grenade was passed. However, the grenade might still be rejected for many other reasons.

To all intents and purposes the No.5 was hand crafted, and both raw casting and finished article rejection rates were high (typically around 30% quoted by some firms). A number of manufacturers expressed their dislike of it for being a troublesome item to produce. After the war, Frederick Vickery, Managing Director of Vickery's Patents Ltd, and a highly competent engineer, described the No.5 as "a thoroughly bad mechanical job". His efforts, along with those of James Gibbons, produced the No.23 MkIII and No.36, which far from being a mere improvement, was a substantially different grenade (in terms of manufacture, filling and safety of use) to the No.5 family.


Tom.

 

[siegfreid]

Tom.
Brilliant information . Just as I suspected , the No5's were not in the finest tradition of British engineering ! I'm sure there are many collectors out there that will look at the examples they have in a different light . Keep up the good work on the research . Mike