Japanese helmet sizes for homework assignment

[Dean Brock]

10

[Striking 9th]

Man is that a nice pick up Dean! How does it look with the cover on it? Well done.
Scott

[Jim B.]

Jim thats good info! I just had a conversation with Eric Doody regarding navy helmet sizes. Eric suggested that you'll find differences in shell sizes (measurements length/width) depending on the manufacturers. Certain shells were arsenal made & others were contracted out.

BTW, the dimensions I supplied above are for Army helmets I've seen. I guess it's even possible that the army and navy had different drawing callouts and tolerances. The fabrication process couldn't be that accurate, so I would guess that 2mm is probably the tightest we might expect. Eric's comment makes sense. Each contractor would have their own tooling, each of which would supply parts based on slightly different nominal dimensions. There would also be variations from operator to operator, etc.

A common policy in manufacturing is to set slightly tight tolerances on the blueprints *knowing* that the contractors will violate them sometimes. You can then buy off batches that run slightly out of tolerance, maybe telling the contractor not to do it again, or maybe not telling them about it so they won't be tempted to push even further out of tolerance next time. So I'm guessing that some helmets are also going to represent "out of tolerance" parts that were ignored, not caught, or approved for use by engineers.

Jim

[John Gordon]

I have seen references in some books to 3 sizes for Army helmets though I dont recall ever seeing a pic of one. Other than slight variations in manufacturers tollerances, has anyone seen/owned a "medium" sized Army helmet to confirm the dimensional differences. I read somewhere that a small helmet might be adjusted to medium through the soldier removing the padding pillows to gain a few millimeters of size. While on the topic of dimensions, is anyone aware of differences in the thickness of metal used in the shell between different manufacturers?

[Banzi64]

And machine die wear would change as more were produced