The idea for this project stemmed from adding three square posts to the lathes faceplate
one of which had a clamping jaw as those seen later Photograph 1. The idea was to
use it as an alternative to the Keates angle plate. However, it was difficult to
set the workpiece to the position required there being three posts to adjust.
I largely overcame this by using four posts enabling the workpiece to be set one
axis at a time. This worked much better but the clamping force available bowed the
faceplate causing the jaw faces to splay a little at the outer ends. I considered
though that this could be the basis of a design if using a much more substantial
face plate and from these findings the subject for this project was developed. This
being seen in Photograph 2.
The drawings I have included suit a Myford series seven or any other similar size
machine having a threaded mandrel nose, but in this case changes are likely to suit
the lathe's mandrel. The design though is so simple that it should be easily adaptable
for both smaller and larger lathes, also, for lathes having a flange mounting arrangement
for its chucks, etc.. Some, who may likely use a four jaw only very occasionally,
may even make one in place of purchasing a commercial chuck.
The body (1)
This is made from a piece of 150mm diameter cast iron bar which I chose in favour
of mild steel as it would be easier, if dirty, to machine the tee slots using my
home made silver steel tee slot cutter having done this a number of times previously,
I did though eventually use a purchased cutter.
Drill and tap four M6 holes on a 100mm PCD and use these to secure the material to
the lathe's existing faceplate, do though check these dimensions against your faceplate
before proceeding. Also, ensure that the face is reasonably flat though in the case
of a very small error the faceplate itself will distort, not the material with this
being much thicker. However, if the error is substantial then machine it flat on
the milling machine, though as the material will have been sawn from a bar such an
error is unlikely. When mounting the material on the faceplate space it off with
thick washers, say 5mm minimum, as this will permit the boring and thread cutting
tools to break into the gap, Photograph 3.