Milling Spur Gear on Milling Machine

The gear blank is mounted on a mandrel which is supported between the center of the dividing head and one more center at the other end, as shown in fig. At a time one tooth space is cut by the milling cutter, and a dividing head is used to index the job to the next required tooth space. The cutter is chosen according to the module (or DP) and number of teeth of the gear to the cut. This cutter is mounted on the milling arbor. Before the gear can be cut, it is necessary to have the cutter centred accurately relative to the gear holding mandrel. One way is to adjust the machine table vertically and horizontally until one corner of the cutter just touches the mandrel on one side. Both the dials (of the table and the knee) are then set to zero. The table is then adjusted for the cutter to just touch on the other side of the mandrel with vertical dial showing zero. The reading of the horizontal feed screw is read. This reading divided by two gives the central position of the mandrel relative to the cutter. When the table is set centrally in this manner it should be locked in that position. The table is then fed vertically so that the blank just touches the cutter. The vertical dial is then set to zero. This is required to give the depth of cut on the job.

With these settings the machine can be started and traversed along the axis of the job to cut the tooth over the whole width of the gear. Depth is increased slowly until it reaches the full depth of the tooth. With the depth setting the backlash of the gear can be controlled suitably. After one tooth space is cut, the blank is indexed through 1/z revolution by means of the dividing head, and the process is repeated until all the teeth are cut.