With those precautions having been taken note of, I machined the two faces as shown
in Photograph 2 , having set them reasonably level so that they were machined equally.
I often comment that relying on a single clamp is to be avoided if possible and that
one too many is much better than one too few. In this case though, the compact nature
of the assembly made it acceptable, do note though that the machining forces are
towards the angle plate, not away or across. I did consider that some workshop owners
would not have an angle plate large enough to permit more clamps to be employed so
decided that I would like to illustrate a method within the bounds of what would
likely be available in some cases.
It may seem obvious that the next face should be the large main face but I decided
that the top of the web should now be tackled. The reason being that it was very
likely that the main face and the top of the web, would only be nominally parallel,
so by machining the web first the two surfaces were trued up with the minimum of
metal removed, Photograph 3.
Next, I chose to mount the casting onto two square posts when machining the main
face, Photograph 4. To do this the surface machined in the last operation was placed
firmly on the machine table ensuring that the larger face now being machined was
parallel with the top of the web already machined. It is worth considering that posts
such as these can find many uses on the milling machine so are worth making. You
will see that I have used a form of clamp that I rarely use but their pivoted end
piece makes them ideal for dealing with the slightly sloping surface of the casting,
again note that the cutting forces are towards the posts. Whilst the casting is setup
in this way it would appear an obvious time to make the two slots, but as they need
to be equally spaced about the vee, not yet machined, and being super cautious ,I
delayed the process just in case the vee did not end up in the position I anticipated.
Next task was to machine the faces of the vee being, I thought, a relatively easy
operation other than to measure the result during the operation. Unfortunately though,
I had overlooked the fact that the projection of the cutter from the milling spindle
was insufficient to avoid the top edge of the casting fouling the underside of the
milling spindle. I could have used an old high speed steel end mill in the cutter
chuck which would have given me the necessary clearance and would anticipate that
this would be the method chosen by most. Having machined the surfaces at either
end of the vee about to be made the cutter would not be breaking through a hard skin
so would not anticipate too much of a problem with the method.