Tipped tools having a tip with a curved edge, and an end mill characteristic, therefore
produce a true vertical face, are available, Photograph 8. Having removed the cast
iron skin I could have finished the surface with a HSS end mill but chose to do it
manually with a wide fine file.
Finishing the main faces
Having now rough machined all the surfaces, set up each casting as in Photograph
4 and finish their main face, if you have a tipped tool with a round tip this will
achieve a better result. To avoid having to machine too much from the faces they
do need to be set level fairly accurately, see Photograph 9 for a method of achieving
this. Of course, once the casting is secured the two plates and parallels are removed
so that machining can proceed.
Drilling the lugs
The next stage is a critical one and if not done with care the base and working face
will not remain accurate relative to one another when differing angles are set. First,
set one angle plate accurately at right angles to the traverse of the table by using
a square off the front edge of the table and then a second angle plate at right angles
to the first, Photograph 10, they do not need to be identical plates.
With the two castings added, Photograph 11, they need to be accurately positioned
relative to the machines spindle using an edge finder of some form, typically, one
with a lamp as seen in the photograph. Do ensure that the castings mate together
perfectly, that is with the eventual lower end of the large casting being level with
the main face of the smaller.
The drawings state a dimension of 38mm for the height of the hole in the lug relative
to the angle plate's faces. However, this is based on the thickness of the plate
being 16mm but having finished machined the faces my plates were still 18mm thick
and I saw no reason for reducing it further. This also, as the extra thickness would
be beneficial with regard to another modification I had in mind. I worked therefore
to a dimension of 40mm.