Whilst the obvious choice will be to use a fully machined angle plate to support
the casting for machining I am using a method I adopted for machining precision angle
plates. This is to use a form of "Cylindrical Square". The advantage of this is that
it is very accurate and is a viable method for the workshop owner who is yet to obtain
an angle plate. Providing the cylinder is turned exactly parallel and the base machined
in the same sequence then the cylinder will stand perfectly square to the machine's
table and may therefore be more accurate than an existing angle plate that may have
aged a little since is was first machined.
Photograph 5 shows the first of the two main sides being machined in this way whilst
the second side will be set up in much the same way but the parallel will not be
used due to the curved surface. All that will be needed is to set the top face reasonably
level to avoid more being machined from one end than the other Photograph 6.
With the two main faces machined then the ends can be machined, again using the two
cylinders as Photograph 7 illustrates. This automatically results in the end being
perfectly square to both main faces, something that would be more difficult to achieve
if using a single angle plate to mount the casting. The "Cylindrical Squares" were
made for a smaller milling machine with smaller T slots and a larger diameter would
have been preferable in this case but even so they stood perfect square to the table's
surface when checked with a precision square.
Mark out the base for the five fixing holes and drill and counter bore as per the
drawing, Photograph 8. Five fixings would appear excessive but no doubt in use only
three fixings would be used the additional holes just giving some flexibility.
If used as machined so far, then on a Myford Seven the lathe's gap is just insufficient
to permit the angle plate to be used fully to the edge of the faceplate and the corners
of the main face need some small rebates machined in them, at this stage I have chosen
not to do this.
The Lathe Only Workshop.
The method proposed by Hemingway, whilst a little slower, does have the advantage
that it suits the lathe only workshop owner, as I said earlier there are though some
similarities with the method I used.