M-1 Helmet Shaping Operation II – Trimming Operation

Big Red here with a question from "Lloyd Christmas"...

    So, TAKE FIVE!

    Lloyd asks,

    "Big Red, At what point in the process did helmets undergo the Trimming Operation?"

    Good question Lloyd…….So, let's look at the process thus far....

    The steel maker rolled out helmet steel, cut the sheets into 16 ½-inch discs, coated them with oil and banded them into bundles of 400 for delivery to the fabricator for processing. Discs were assigned a “lot and lift” number upon receipt at the fabricator and were sent to a small punch press where their assigned number was embossed in each sheet with a fine-line stamp. If selected discs from the lot passed the initial steel quality inspection, they were delivered to large presses that pressed the discs, two or three at a time, into 7-inch deep pots in a single operation.

    These freshly pressed helmets retained the excess metal, called "hold down" from the disc, which formed a brim around their edges. The Trimming operation was used to remove the hold down.

    So, the first major operation was the initial deep draw followed by the second major operation which was the trimming operation.


    Of special note:

    The hardness achieved in the steel after the initial draw approached the hardness of the steel used in the trimming dies. This reality made the occurrence of chipping or nicking of the trimming dies extremely common. Damaged trimming dies left small notches on the edges of the helmet and the highly stressed nature of the visor area made it extremely susceptible to immediate or delayed cracking if notches were present.

    Notches left in the area of the helmets visor was the primary culprit behind the phenomenon of “Service Cracking” a.k.a. “Age Cracking” in the production of the M-1 helmet. Determining the cause and finding ways to prevent Age Cracking occupied a significant amount of time, money and effort on the part of all the specialists involved in the fabrication of the M-1 helmet.

    Sure thing Lloyd, I see you got both the trimming and the chipping down pat!

    Remember Lloyd,

    if your friends want to know how you gained your intel, tell em


    Big Red Says!


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