Harold Hall

Workshop Processes



Hole boring

Sometimes it may be required to make a cut whilst the table rotates fully through 360°, either to bore a hole as in Photograph 19, or to produce a disk from a larger sheet. As the sheet may project from the edge of the rotary table it may be too large to swing on the lathe and is a useful alternative method.


The example in the above photograph is of the plate being bored onto which the chuck seen in photograph 15 is to be fitted. As this is just clearance for the boss on the rear of the chuck accuracy was not a requirement. However, as can be seen in the photograph, the rotary table was also used to position the three holes on a PCD for the chuck's fixings. Incidentally, do not be puzzled by the additional holes, these are there as it was being made from a piece of scrap that already had them in it.


The machining process

Carrying out the actual machining process follows closely to those when using the milling machine in its normal format, that is, ensure that the rotation of the table opposes the rotation of the cutter. However, do ensure that you have adjusted your worm/worm wheel engagement to limit backlash to a minimum. If this is not done then the cutter may grab the workpiece when it is returned to the start for a further depth of cut. This is particularly important when carrying out a task such as the radius along the length of the crank arm discussed earlier.


Having made your locating plugs and specialised clamps do retain these for possible use in the future even if at the time they require modifying for the task in hand. With that in mind see Sk. 4 for my suggestion as to how the problem with the Morse taper centre can be overcome.

Rotary Table Using


The viewer may find  my book The Milling Machine and Accessories, Choosing and Using Number 49 in the Workshop Practice Series of help as it covers the Rotary table in depth and all other aspects of choosing and using the milling machine and its accessories.


Doing this  from the very simple, workpiece clamps, to the very complex, dividing heads, and all aspects of the machine in between.