This is a direct action and graze fuze with a plastic body and is used in 5 cm, 8 cm, and 10 cm H.E. Mortar bombs. The fuze may be identified by the stamping "Wgr Z T" above the flange. An exterior view of the fuze showing stampings is illustrated in Fig. 2.

The principal parts are the body, needle, needle spring, inertia pellet with detonator, a large segment housing a detent arming arrangement, a small segment with an irregular groove, and a base closing plug.

The plastic body is reinforced at its forward end by embedding in it, a thin perforated sheet of metal shaped to a cone and joined by a metal clip. The body is bored centrally in three diameters. At the top two chambers, separated by a diaphragm accommodates the needle, needle holder and spiral spring and below these chambers, another accom-modate the fuze mechanism. The top of the fuze is closed by a laminated plastic disc.

The head of the needle is embedded in a plastic holder which has an annular recess on its underside to form a seating for one end of the needle spring. The stem of the needle passes through the diaphragm which also provides a seating for the other end of the spring.

The inertia pellet consists of a white metal detonator holder, upper and lower plastic bushes, creep spring, detonator and plastic washer. The detonator holder is cylindrical, has an internal flange at one end, and is bored centrally in two diameters to form cham-bers which accommodate the bushes, spring and detonator. The upper bush has and ex-ternal flange and is inserted in the holder from the bottom so that its smaller diameter protrudes and forms a guide for the point of the needle. It is retained in this position by the spiral creep spring. One end of the spring is seated against the shoulder of the upper bush whilst the other is seated on the shoulder of the lower bush. The lower bush, as-sembled from the bottom, bears against an internal shoulder in the detonator holder. The detonator is held between the lower bush and a plastic washer which is secured by turn-ing the base of the holder over the washer. A stud on the outside of the pellet engages a groove in the smaller of the two plastic segments surrounding the pellet. Diametrically opposite the stud, the forward end of the pellet is cut away to partly accommodate a ball which locks the pellet in the unarmed position.

The large segment accommodates the arming arrangement which consists of a metal de-tent, spiral spring, plastic seating disc, steel ball, U shaped spring and a detent catch.

The detent is cylindrical, partly tapered towards a flanged base and has a flat on one side. It is accommodated in the top of a long chamber and its forward movement is limi-ted by the flange which bears against a shoulder in the chamber. The flat retains a ball in a radial hole, thus locking the inertia pellet in the safe position. The detent is retained in this position by the spring which has a seating disc at its base end. A shorter chamber accommodates the inverted U shaped spring and detent catch. The catch is held bet-ween the spring and two longitudinal projections formed in the segment.

The base of the fuze is closed by a screwed plug with a transparent disc closing the flash hole.

Before firing. – The inertia pellet containing the detonator is locked and held away from the needle by the steel ball.

On firing. – The detent sets back, and its flange is engaged and held by the detent catch under the action of its spring, thereby freeing the ball and releasing the inertia pellet.

During deceleration, the inertia pellet creeps forward but, through its stud, its movement is controlled by the irregular groove in the small segment. The pellet creeps forward until the upper bush bears against the diaphragm surrounding the needle. Further creep is then prevented by the creep spring.

On impact the needle holder compresses the needle spring and forces the needle on to the detonator.

On graze the creep spring is compressed and the detonator is carried forward by its hol-der on to the needle. The flash from the detonator passes through the flash hole in the closing plug to the gaine in the shell.

Fig. 2