In most of the methods of cutting cam, first the cam contour has to be scribed on a cam blank. Then the following methods could be used :

(1) On drilling machine : In this method first the points are prick-punched around the periphery of cam at a distance of half the drill diameter plus small clearance of about 0.5 or 1.0 mm. These prick-punch marks are then punched deeper. Using a drilling machine, holes are drilled all around on the punched marks and the scrap material broken away and the surface file finished to the finish line of the cam contour. Final finishing operation may be done by sanding with a sanding disc held in a drill-press chuck. This method is used to cut a master cam.

(2) Once the master cam is made, other cams can be cut on a duplicator or other special machines.

(3) Cam grinders can also be used to finish the cam surfaces using a master cam. This operation is carried out after cutting or filing the cam on duplicator machine.

(4) Numerically controlled machines can also be used to cut a cam by suitable programming. The co-ordinates of many points on the cam surface are fed into a tape.

Using universal milling machine having [vertical attach­ment and the universal dividing head. This is the most widely used method for cutting master cams. In this method the dividing head is geared to the milling machine lead screw for cutting a helix and

an end mill mounted in the vertical attachment. The dividing head is rotated into the vertical position so that the cam surface is parallel to the centre line of the cutter (as shown in Fig. 16″47). It is impor­tant to note that the centre line of the cutter must always be parallel to the centre line of the dividing head. Now the table will move the cam into the cutter as the cam rotates. Depending on the lead of the cam, i.e. the rise in its surface over two angular positions, the gear train connecting the dividing head and the milling machine lead screw can be suitably chosen. If 2.5mm be the pitch of the lead screw and change gear ratio as unity then in one rotation of the dividing head or cam, the table will move 2.5×40=100 mm or a lead of 10 cm will be made on the cam. Changing the gear ratio, it is possible to obtain any lead of the cam. If a cam has two or more lobes then their leads over certain angular movements can be calculated and either the desired lead be obtained by changing the gear ratio, or choosing the gear ratio for higher lead, and for small lead the dividing head and the cutter position be inclined at angle θ with table. In that case, the lead on the cam will be lead of table x sin θ.