EMPLOYMENT: Mechanical Impact Base Fuze for Polish 3.7-mm A.P. shell. (See fig. 605.)

DATA:

Over-all length: 2.0 inches.

Maximum diameter: 1.0625 inches.

Threaded length: 0.5 inch.

Number of threads: 7 LH.

CONSTRUCTION: The upper body, which extends into the projectile, houses a fixed firing pin and a chamber into which is slipped a detonator pellet with a detonator on top of it. The lower body is threaded to engage the threads on the projectile. The detonator pellet has two indentations on the side to hold locking balls and a groove near the base which engages three vertical extensions of a spring which surrounds the pellet. Compressed composition explosive beneath the pellet acts as a booster. Surrounding the base of the detonator and the small spring is an iron ring, on the outside of which is fitted a stirrup spring. Near the top of this ring, are two holes for holding the locking balls. The two locking balls engage the indentations in the detonator pellet and are positioned by a brass ring which surrounds the whole assembly.

ACTION: Set-back causes the brass ring to bear against the stirrup spring located out-side the iron ring. When set-back has been overcome, the brass ring has been driven to the base of the fuze creating a clearance into which the locking balls are thrown by cen-trifugal force. The detonator pellet is now held only by the three spring extensions at the base. On impact, inertia forces the detonator pellet of free itself from these spring ex-tensions and to move forward against the fixed firing pin in the top of the fuze.

Figure 605 – W. Z. 36