Mk 12 Mods 0-3

Projectiles used in

Over-all length, inches

Diameter, inches

Threaded length, inches

Threads

Material

Weight, grams

Arming speed, revolutions per minute

Description: The fuze consists of a nose and a fuze body, held firmly together by a metal jacket, which is crimped over at both ends, and separated from each other by a thin metal disc. The firing pin and firing pin detents are assembled in the nose portion, while the lower body portion of the fuze contains the rotor detent, rotor, detonator, and booster. The booster is held in the base of the fuze body by a metal closing disc, which is secured in position by the crimped-over ends of the fuze body.

Operation: In the unarmed position, the striker is held upward by a pair of firing pin detents, and the detonator rotor is held out of alignment with the firing pin and the booster lead-in by a rotor detent. When the projectile is fired from the gun, centrifugal force moves the firing pin and rotor detents outward against their springs, unlocking the firing pin and the rotor. Centrifugal force then causes the rotor to revolve about its pivot until brougth up by the stop pin. In this position, the detonator is fully aligned with the firing pin and the booster lead-in. On impact, the exposed firing pin is driven into the de-tonator, which initiates the booster lead-in and the booster. The fuze is designed to function on light duralumin sheets.

Remarks: The Point Detonating Fuze Mk 12 Mod 1 is identical to the Mk 12, except that an extra striker-support piece is set in a groove in the nose. Mods 0 and 1 are now obsolete. Mods 2 and 3 differ from Mod 1 in that the striker is held in the nose assembly by crimping over the end of the nose. In the modified Mk 12 (Mods 2 and 3), to decrease the sensitivity of the fuze, a washer has been crimped above the washer. Thus on im-pact, both the crimp and the washer must be broken.

Figure 81. Point Detonating Fuze Mk 12 Mods 0 - 3