Even though I believe that most will purchase a closing ring, making just the holder
to suit their particular lathe mandrel nose, I am including drawings for the closing
ring should the economics of purchasing one change. Of course, as I commented, the
ring has some complications and some viewers may like to attempt to overcome these
as a challenge. The dimensions on my drawings have been taken from the rings I have
and to the best of my abilities, and equipment. I cannot guarantee that they are
precisely to the written standards that obviously exist. For those who would prefer
a smaller version of the chuck, closing rings for at least ER20 and ER25 sizes are
If you are purchasing a closing ring then there is just one item to make, the Collet
body, if not, then two, or three if you include a wrench.
Lathe Collet Body.
The drawings as dimensioned suit the spindle nose of a Myford series seven lathe
and may need modifying for other lathes having a similar chuck mounting method. The
manufacturing method will though be identical. However, I am not detailing the method
in depth here but if needed see for guidance
If not already available do make plug and thread gauges to check both the internal
parallel bore and the thread making them as close a replica of the lathes nose as
is possible. Photograph 3 shows typical examples. Whilst the parallel bore needs
to be made a very close fit the thread can be a little on the loose side allowing
the parallel portion to provide the chucks location.
The plug gauge should be as close to the lathes mandrel diameter as is possible,
but must not be under size as you may end up with a bore that is smaller than the
lathes mandrel which would of course make it impossible to fit.
Now, place a piece of material in the four jaw and knurl the outer diameter, make
the internal thread and parallel bore, Photograph 4. Before removing the part from
the chuck transfer it to the dividing head and drill the holes for the Tommy bar,
Photograph 5. Click on this link should you be interested in details for making the
dividing head seen in the photograph.