It could be considered as a vertical shaper, having only vertical movement of ram. It is generally very robust machine and there is also a possibility of tilting the ram by about 15° from its vertical position to permit machining of dies with relief. This feature is often used when cutting clearances in metal stamping dies.
It is mainly used for internal machining of blind holes or vertical machining of complicated shapes which are difficult to be produced on horizontal shaper. It is very useful for making key ways, machining in square holes, cutting of internal and external teeth on big gears, machining of dies, punches etc. The job is generally supported on round table which has a rotary feed in addition to the usual table movement in cross-directions. The stroke of slotting machines ranges from 300 to 1800 mm.
The ram can be either crank driven (slotted disc type as shown in Fig. 14.29 or hydraulically driven. Ram speeds usually range from 2 to 40 m/min and longitudinal and transverse power feeds range from 0.05 to 2.5 mm/stroke. Cutting action takes place in downward stroke. The pinion which is in mesh with the main gear gets its drive from a pulley run through the belt by motor.
The gear is coupled to the slotted disc. The circular motion of the slotted disc is converted into the reciprocating one with the help of connecting rod. The crank pin can be firmly set in a slot in the slotted disc at different distances from the centre of the slotted disc for varying the length of arm stroke.
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The position of the stroke is adjusted with the help of hand lever provided for the stroke adjustment. Slotting machine is usually provided with horizontal circular work table, but co-ordinate tables are also provided sometimes. The table is mounted directly over a bed casting and fairly heavy work may be placed.
Depending upon the functions for which slotters are designed, they could be classified as:
(i) Puncher Slotter:
It is of rugged construction, equipped with a powerful motor and can machine cut metal at a very high speed, on it without serious distortion. Circular table can be revolved by hand or power teed. It is graduated round its outer edges, and work can thus be mounted and turned to predetermined position.
(ii) Production Slotter.
(iii) Tool-Room Slotter.
In this case circular table is mounted on a pair of slides arranged on a saddle, and this saddle itself moves on another pair of slides on the bed casting. Thus, work can be revolved and also moved in two directions at right angles to each other.
Relieving tool used with slotters. Fig. 14.30 shows a relieving tool used to produce large internal surfaces from drilled holes. This tool, circular in section, nibbles at the hole and can cut in every direction at right angles to its axis as shown is Fig. 14.30.
