Machine what will be the rear of the body and then bore and thread to suit the lathes
spindle nose. It is all but essential that you make a gauge to test the locating
diameter and whilst a little less critical a gauge for the thread also would be a
good idea. The thread is a little less critical as it needs to be slightly on the
large size to ensure that location of the finished body will be on the locating diameter
unaffected by the fit of the thread. If you would like guidance on this operation
see my pages elsewhere on the site.
Now remove and fit to the lathe's mandrel and machine the face flat also skim the
outer diameter and lightly chamfering the two outer corners. This completing the
turning requirements for the time being. I have given dimensions for the outer diameter
and body thickness but there is no need to work to these slavishly, once the surfaces
are clean that will suffice.
Before producing the T slots a decision has to be made whether to make just the four
for the jaws or also to include the additional ones to provide extra facilities for
holding the eventual workpiece. The viewer will see from the photographs that I have
included all eight as once one is set up for making the slots making the four additional
ones is a relatively quick operation. My advice therefore is to make the eight slots
and will describe the operations on that basis.
Machining the T slots
If the viewer has a rotary table large enough to use for positioning the slots then
this is the obvious the way to proceed but as I consider most will not have this
facility then another method has to be used. At first, this would seem a rather daunting
task with the cutter having to be accurately located and table stops set for each
slot individually. However, the method I eventually came up with avoided such a problem
and the slots were made very easily, probably as easy as using a rotary table. The
secret of its success is in the way the body is mounted onto the machine table enabling
it to rotate.
Marking at 45°
First, the body must be marked at its edges at 45° intervals, but how this is achieved
I have included on in Sk.1, see also Photograph 4. I would just emphasis the importance
of placing one of the original fixing holes 16mm above the centre line on the right
hand side as this ensures that they are machined out when the slots are eventually