Big Red here with another question from "George Foreman"...
So, TAKE FIVE!
"Big Red, I was told that the German Stahlhelm took 7 pressings to shape. How many pressings did it take to shape the M-1 helmet?"
Great question George...
The same as the number of punches it takes to make a heavyweight champion...
The M-1 helmet program began with an experimental run to see if the helmet could be made from a flat disc of Hadfield manganese steel in a single operation on a large press. Little if any actual investigation was made into the feasibility of doing so in a large-scale mass production environment leaving the early days of manufacturing governed by trial and error. The, now iconic, shape of the M-1 helmet was created from a flat sheet of steel in three major press shaping operations.
In order to obtain the necessary 7-inch deep draw, the process began with a 17-inch diameter disc that later, was determined could be reduced to a diameter of 16 ½-inches. These discs arrived at the fabricator on freight cars and were received according to the heat of steel and lift numbers that were printed on each disc by the steel maker. Each disc was assigned a lot and lift number by the fabricator that was fine-line stamped into each disc so they would carry through the entire fabrication process and remain as a permanent record of the steel going into each helmet.
Discs were then delivered to giant presses where they were placed into position inside the press by an operator or a team of two operators depending on the number of punches the press contained, one, two or three.
Each disc is placed into a hold-down ring clamp to secure it over the lower die. The lower die was a ring into which the punch die would descend. The punch die made of high-carbon cobalt steel and later of high-carbon high-chromium air-hardening steel, was attached to a ram that pressed down into the lower die to form the shape of the dome.
All the working of the metal is done by the punch and hold-down in a single operation without heat in order to cold work the disc into the desired shape and at the same time harden the steel sufficiently to meet ballistic requirements.
Big Red Says!
FIVE'S OVER - MOVE OUT!