Harold Hall
Workshop Processes
Vitally Important
Whilst photograph 14 shows how a chuck can be mounted there are limitations to its use in this way. If, for example, the workpiece seen in photograph 4 had been held in a chuck on a threaded adaptor then the action of milling the hexagon would be attempting to unscrew the chuck. This would certainly happen resulting in a damaged workpiece and broken cutter being highly likely. Its use typically would be to place holes on a PCD.
Positioning the rotary table and chuck (screwed on or with a back plate) will follow the same principles as with the Keats angle plate. However, a centre drilled plug, temporarily held in the chuck, would be required if the workpiece could not provide this facility.
For lighter applications the lathe's collet chuck could be used with the adapter seen in photograph 14, Photograph 16 showing an example. In this a small hand wheel for a model machine tool is having 4 holes drilled on a PCD.
Other methods of holding the workpiece, such as a vice or angle plate, will still have the essential requirement of positioning them on the rotary table to achieve the required aim. As the possibilities are numerous, it is impracticable to attempt to add any detail, the above suggestions should though point you in the right direction. I will though add that if a vice is to be used then a toolmakers vice is the ideal choice. This is because its unique method of fixing it to the machine table gives much more freedom in positioning it, a situation that should be evident from Photograph 17.
Vertical Use
Using the rotary table in the vertical position will be for most an infrequent method
and then the task is likely to be rather specialised, Photograph 18 though shows
a typical example. In this, a shaft is having a grove milled only partially around
it periphery which in the final assembly will engage with a fixed pin to limit the
shaft's rotation. Another example, but one that could also be done using a dividing
head should one exist in the workshop, would be to machine a hexagon on the end of
a shaft using a similar set-
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