Having machined the first end turn over and machine the second end similarly. Do
in this case ensure that the first end is firmly in contact with the milling machine
table. Repeat for the second casting. Do not be concerned with dimensions the machining
is just to achieve a reasonably clean face, but any shallow blemishes left will be
removed at the finishing stage.
We now come to a major problem, at least for most I would assume. The main face now
needs to be machined fully so overhead clamps are out. If the viewer has a split
vice this would be ideal but will need jaws at least 55mm deep due to the lugs on
the rear of the castings. After much consideration I came up with the idea of using
two angle plates and using two long studs between them to achieve the required grip.
Photograph 4 show the set up with the part being partially machined. Setting it level
for machining is not critical but would suggest using three jacks made from a T-nut
and a screw for setting and holding it sufficiently level whilst the part is being
clamped, the jacks serving no purpose once the part is secured.
If the viewer does not have two identical height angle plates then the taller can
be spaced away with a piece of packing just wide enough for the cutter to pass the
casting's edge. Again the process is repeated for the second casting. I would suggest
that two identical angle plates are a worthwhile addition to any workshop as they
can often find a use together.
Mount the casting again generally as shown in Photograph 3 but this time with the
long edge horizontal and machine the edge. Do ensure that the short edges are at
right angles to the machine table. Turn over and repeat the process but this time
with the long edge on the machine table or suitably raised using a parallel if the
angle plate is too high.
Mount the main casting, the larger one on which the workpieces will mostly be mounted,
onto the machine table and machine the edge as in Photograph 5. The purpose of this
is as an accurate surface for the edge of the base casting to mate with. Whilst not
detailed on the drawings it is likely that a similar, but much narrower, strip will
be needed on the base casting to ensure the two castings mate adequately.
Revised hinge design
This now leaves the lugs to be machined on their inner and outer faces. However,
I chose to revise the method for the hinge assembly as shown on the CES drawings
as I was not confident that I could easily achieve the fit between the inner and
outer lugs that I feel is essential.