Harold Hall

Workshop Processes


Having machined the three jaws thus far the second side of each tooth has to be machined. The process is very similar to that already carried out except that the position of the cutter relative to the jaw is much more critical and that it will be cutting on one side only. Do not forget to change the offset though if needs be and change the radius at which the cutter works. With regard to the latter, having previously worked out the two values, calculate the difference between the two and again traverse the cross feed by this amount. As you are now machining the inner curve which is the flatter of the two, the radius has to be increased. Do ensure that you move the cross slide in the correct direction. Again lock the table and remove the handle.


Set the inner fence so that after machining the first grove the resulting tooth width is definitely too thick. Measure the result to determine how much more has to be removed, measuring the chucks normal jaws to determine the required value. Use the screw in the inner fence to make the adjustment required and re-machine and measure the result. With the thickness of the tooth established machine the rest of the teeth and the other two jaws.


As the cut now only takes place on one side of the cutter reversing it will cause the cutting edge and the workpiece to move in the same direction, rather than opposing each other as is preferable. The back lash present may permit the cutter to grab the workpiece and move it forward rapidly, with such a small cutter it is likely that it will be broken. As the cut is relatively light it will be easy to avoid this possibility by using one hand to restrain the rotary table sufficiently to avoid the backlash being taken up. With the teeth on the jaws finished the difficult bit is done.



I say difficult and feel that the process is so easily open to errors and therefor wish to emphasise the following.


The offset may vary from one side of the tooth to the other, do ensure you calculate both and if so ensure you use the appropriate plug in the rotary table in each case.


The radius of the tooth also varies from one side to the other so do ensure that you reset this when machining the second side.