Nose Fuzes No. 846 Mk I and No. 879 Mk I (Service)

Description: The Fuze No. 846 consists of a machined fuze body, bored centrally to house an inertia pellet, which contains the detonator and flash channel, a safety ferrule, a creep spring, and a fixed striker, which is riveted into the fuze body. One end of the creep spring rests against a shoulder on the inertia pellet, and the other end is located in a circumferential groove in the bore of the fuze body. The flash channel in the inertia pellet leads directly from the detonator to the magazine.

A magazine ring is threaded and cemented onto external threads on the base of the fuze body. A magazine containing a gunpowder charge is crimped to the ring. The maga-zine is closed by a cupped washer, the hole of which is aligned with the flash channel in the inertia pellet and is covered by a paper disc.

A hole in the fuze body at right angles to the central bore houses a retaining ball, and is closed at the outer end with a screwed plug. The inner end of the hole is of reduced diameter to permit the ball to protrude into, but not fall into, the central bore. A second hole, parallel to the bore, intersects the transverse hole and houses a transit safety pin, which retains the ball in such position that it projects into the bore and prevents the inertia pellet from accidental contact with the striker. The safety pin has a ring passing through its head to facilitate its withdrawal from the fuze.

The fuze has no external threads for fixing into the bomb, but is held in place in the fuze pocket by the threaded nose plug. Two recesses are bored in the boss of the fuze to engage two projections on the base of the nose plug. This locking arrangement ensu-res that the safety-pin hole in the nose plug is properly positioned over the safety pin and safety-pin hole in the boss of the fuze.

Operation: The transit safety pin in the fuze is removed and replaced by a longer safety pin, when the fuze is assembled in the bomb. This long safety pin is removed ma-nually when the bomb is placed in the Small Bomb Container before loading into the plane. The fuze is then armed. On impact with the target, the inertia pellet overcomes the resistance of the creep spring, bends the tabs on the safety ferrule, and impinges against the striker, to fire the detonator. The flash from the detonator passes through the flash hole in the inertia pellet, and  fires the gunpowder magazine, which initiates the bomb.

Remarks: Normally these fuzes are shipped in place in the bombs, thus requiring the long shipping safety pin.

The Fuze No. 879 Mk I is identical to the No. 846 Mk I except that it has five grams of aluminum powder in the burster well.

Figure 157 - Nose Fuze No. 846 Mk I