The fuze is used in H.E. shell for a number of equipments and is of the igniferous type, with a graze mechanism in which the detonator is fixed and the needle is carried in the graze pellet. The body is of 0.97 inch gauge, with approximately eleven threads to the inch. In order to obtain detonation, a gaine is inserted in the base fuze-hole beneath the fuze, the following types having been met with:–

0.89 gram cyclonite gaine

1.8  gram cyclonite gaine

2.3  gram ballistite gaine

For safety transport and storage the screwed brass plug carrying the detonator is not inserted in the head of the fuze. Instead, an aluminium or black composition transit plug is fitted.

The cylindrical brass body is screw-threaded throughout its length for insertion in the shell, and has a flange at the head which is only part protruding from the fuzed shell. A screw-threaded hole in the head receives either the detonator plug or transit plug and leads to the interior recess containing the graze mechanism. The diameter of this recess is increased to form a shoulder near the base which locates the retaining collar, and be-low the shoulder it is screw-threaded to receive the magazine.

The brass arming sleeve has an internal circumferential groove to engage the prongs of the arming spring when in the armed position, and is fitted over the head of the graze pellet, where it is supported by the arming spring. In this position it prevents the needle moving towards the detonator.

The arming spring consists of a brass ring which fits over the forward end of the graze pellet and is shaped to form three prongs or arms which support the arming sleeve.

The brass graze pellet is in the form of a cup with two recesses cut diametrically oppo-site in the wall at the mouth to receive the needle bar, which is of steel, with a pyramid pointed needle formed at ist centre. A flange formed round the base of the pellet is cut away at four equidistant positions, with a semi-circular chamfer on the underside. At each of these position an inclined flash channel is drilled between the chamfered surface and the base of the interior of the pellet. A hole is drilled through the centre of the base to receive the stem of the sealing plug.

The copper sealing plug is shaped to seat in and seal the flash-hole of the magazine and is provided with a stem screw-threaded to two diameters for the assembly of the stirrup spring and attachment to the graze pellet. The stirrup spring is held between the head of the plug and a brass nut screwed on to the stem immediately behind the head. The up-per part of the stem is inserted through the hole in the base of the graze pellet and se-cured by a brass nut inside the pellet.

The steel stirrup spring has two inclined arms which are engaged by the wall of a conical hole in the retaining collar.

The brass retaining collar consists of a disc, of larger diameter than the recess contain-ing the graze pellet, with a tapered central hole to receive the stirrup spring. The collar bears against the shoulder in the body, and is secured by the magazine.

The brass magazine screws into the base end of the body, and contains a 0.8 grain per-forated pellet of gunpowder. A flash-hole formed in the head is tapered and provided with a soft metal seating to receive the sealing plug. The base is lightly closed by a brass washer, with a fabric disc on its inner side.

The brass plug is mushroom shaped, with a screw-threaded stem for insertion in the head of the fuze and a ring of knurling on the head. A central recess for the detonator is formed in the plug with a flash-hole at its base and a screw-thread in the upper part to receive the closing plug. The detonator is held in the lower part of the recess and has a copper shell closed at the top by a copper disc and at the bottom by a brass disc and white paper disc. The filling consists of a 1 grain pressing of gunpowder with a 1.2 grain sensitizing layer of detonating composition. The composition consists of mercury fulmi-nate 12.4 per cent, potassium chloarte 45.3 per cent, antimony sulphide 39.1 per cent, and grit 3.2 per cent. The recess is closed by two brass screwed plugs, with felt packing inserted between them.

On acceleration the sealing plug sets back in its seating and seals the flash channel, thus affording protection should the detonator fire prematurely. At the same time the arming sleeve sets back over the graze pellet and is retained in the set-back position by the prongs of the arming spring engaging in the internal groove in the sleeve. The graze pellet with its needle is then held off the detonator only by the arms of the stirrup spring bearing against the wall of the tapered hole in the retaining collar. On graze the momen-tum of the graze pellet forces the arms of the stirrup spring through the retaining collar and the pellet moves forward, thus causing the needle to pierce the detonator and re-moving the sealing plug from its seating. The flash from the detonator passes through the flash-holes in the graze pellet and enters the magazine. The explosion of the powder pellet in the magazine produces a flash which passes to the initiator filling in the gaine, and thus bring about the detonation of the gaine.