Big Red here with another question from "John Connor"...
So, TAKE FIVE!
John asks,
“Big Red, you referred to what you called a “nasty little production breakage problem” and said the problem had been plaguing the M-1 helmets manufacture from the beginning, what do you mean?"
Excellent question John,
Hadfield Manganese steel is a unique alloy steel containing an extraordinarily high manganese content mixed with high carbon. The principal advantage is that, unlike other steels that must be closely monitored through multiple heat treatments to become strong, it can be drawn into forms such as the M-1 helmet without annealing or heat treatment, and yet afford a high ballistic resistance. This steel has rapid hardening properties when cold worked and is capable of doubling in strength however, if the steel formula is not mixed correctly there will be a high incidence of breakage when forming it.
The old Doughboy style trench helmet only required a 4-inch deep draw to make while the new M-1 needed a 7-inch draw to form its pot shape. At the beginning of the M1917A-1 contract, in November 1940, the Production Engineers at McCord had experienced upwards of 25% draw breakage. Cooperation, between the Engineers and the steel manufacturers Metallurgists, enabled changes in steel and production habits that reduced breakage to an average of 1% by February, 1941.
Based on this short experience with helmet making, McCord’s Production Engineers were extremely concerned that attempting to make the M-1 pot design on a mass-production level, with a single draw, would create a breakage problem on a much larger scale. In March when production on the new M-1 helmet started, all those fears were realized.
Manufacture of the M-1, at the beginning of the contract, experienced production breakage in the initial draw and spanking operations upwards of 30%. After the helmet maximum weight limit was enforced in September 1941, and steel discs were reduced in thickness, production breakage increased to 35%.
Keep those questions coming John!
and remember,
Big Red Says!
FIVE'S OVER - MOVE OUT!
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