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Lathe – techniques – trepanning
Trepanning is the process whereby a round part is cut out of another part by removing a thin ring of material.
It might be done for any one of several reasons. It may be that a hole is required in the larger part yet it is worth keeping as much of the material removed as possible. It may be that the part removed is the part that is wanted but this is the easiest way of doing this.
Trepanning is usually thought of as a job done on the lathe. The workpiece is fitted to the face plate or held in a chuck. The cutter moves in a line parallel to the bed of the lathe.
That’s the easy bit. The real problem in trepanning is the cutter. The cutter will be cutting out in pieces a ring shaped piece. This means that if the cutter is the width of the ring the inside edge of the cutter must not cut into the inside part. Similarly the outside edge of the cutter must not cut into the outside part. At the same time the cutter must be strong enough to reach right through the material. It is also necessary that as small amount of material must be cut, firstly to save time and, secondly, not to waste material.
It is shown elsewhere that trepanning is a process that can be done on the milling machine .
see Trepanning on the milling machine