project report for fabrication of drill jig

SPLIT-PIN DRILL JIG
A commonly-used means for preventing nuts coming loose from bolts in service is the use of split pins. It is is inserted between the castellations of a special castellated nut, and through a hole in the bolt, until the head of the pin fits between two castellations. Then The split ends of the pin are then bent over for locking the nut onto the bolt. A disadvantage of this method is that when the nut is tightened on the bolt, the gaps between the castellations may not line up with the pre-drilled hole in the bolt.
As a solution to this, split pins is used to assemble a nut onto a bolt, tighten it to the required specified torque, and then drill, freehand, through the bolt, using the gap between the castellations as an approximate guide. But If the drill breaks off in the bolt, the rectification process to remove and replace the bolt and nut is difficult and time-consuming.

In this present invention a jig for drilling a split-pin hole in a suitable position, in a bolt which has a castellated nut assembled onto it is provided. The body of the jig may be manufactured from a bar of metallic material which is machined, or otherwise formed, internally to form a hexagonal internal hole. It may also be manufacture from a standard hexagonal socket as ordinarily used for tightening and loosening nuts. he jig has one radial hole through its wall, which hole may be coincident with the centre of an internal flat surface. A drill brush of appropriate size is secured to guide the drill bit required to drill the split-pin hole. In practical use, the procedure is:The jig is placed over the nut and bolt so that the axis of the hexagonal hole in the jig is substantially coincident with the axis of the bolt. The jig is pushed down onto the nut and bolt until a Iocation means, which is part of the jig, engages with the nut and locates the jig in a suitable position to enable the drilling operation to take place. A locating pin may be inserted into each hole.

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