Harold Hall

Workshop Projects


If you are making the spindle at this stage then the 17 mm bore, etc. can be finished in the same way, and at the same time, as the bore in collet chuck body (S8 detailed earlier). If however, the spindle already exists it will be necessary to make a mandrel to replicate exactly the spindle end, Photograph 23. Whilst this is still in the chuck, screw on the adapter and machine the 17 mm bore, 22 mm outer diameter, etc., Photograph 24. Finally, drill for and fit the 3 mm diameter anti turn pin.


Collets L3 You will need one collet for each shank size that  you intend to use. That is from 8 mm, 10 mm and 12 mm if metric and or 5/16", 3/8" and 1/2" if imperial. Place a length of 20 mm dia. (or 3/4"), say 200 mm long, in the three jaw with the outer end supported by the fixed steady. Leave sufficient projecting from the steady to make a single collet.


Machine all the external diameters and bore to suit the shank of the cutter to be used. Make the 17 mm outer diameter a close sliding fit in the adapter, as it is this that ensures the cutter runs true, not the tapered end of the collet in the taper on the closing ring. If you have a number of cutters of the same diameter, measure their shanks and, as shank diameters are permitted to vary a little, choose the largest to use as a gauge for the bore.


Drill through at the core diameter of the thread eventually to be made. However, this thread does not have a lot of work to do so choose a drill size a little on the large side, say plus 0.3 to 0.4 mm. Part off, move steady and make another collet for the next shank size. Using a steady in this way avoids ending up with short stubs of metal in the chuck after parting off each collet. Leave the top slide set at the angle used, for eventually machining the taper in the closing ring. This can now be made prior to finishing the collets.


Closing Ring L2 Place a piece of 40 mm diameter in the three jaw chuck face the end and bore 22 mm diameter to the required depth and a close fit on the adapter, then through at 13 mm diameter. Increase the bore size and cut the 25 x 1 mm thread to be free running on the thread on the adapter.


Now, using the top slide at the angle set for the collets make the taper on the inner end of the bore. However, it will be found that the top slide is not set for machining the taper in the conventional manner. There is though an easy way to overcome the apparent problem, that is to position the boring tool upside down and machine the taper on the back face. This method works perfectly.


Finally, for this part, remove from the chuck turn end of end and return to the three jaw, face end to length and machine the outer taper at the angle already set, though of course it is of no importance.