Next, holding the body's shank in the milling machine vice, machine the 8mm wide
slot in the bottom, seen being carried out in Photograph 13. The short length of
bar is used for aligning the bore with the axis of the machine table. The bar does
not have to be a close fit, the screws clamping it against the side of the bore will
ensure that the bar is in line. It was of course removed before the slot being made
broke through. Also, as the shank had been turned using a tool with a radiused tip,
the body would not sit cleanly on the top of the vice jaws. Because of this, a washer
with a larger hole than the diameter of the shank was placed on the shank to overcome
this problem. This can be seen in the photograph.
There remains just two parts, the feed screw and the dial, that require making before
finally finishing the complete assembly. These are straight forward parts to make
and need no comment from me other than to say make the 20mm dimension on the feed
screw longer, say 22mm, so that it can be reduced gradually on final assembly to
establish a backlash free feed screw assembly.
Finally clean up the parts, removing burrs, etc. and you are ready for assembly,
Photograph 14. This photograph shows the extent of the parts required, including
the tapping jig, and as can be seen there are some complex parts. However, using
the methods described above manufacture of the parts was certainly easier than their
shapes would imply.
One last task is to drill the 3.2mm hole (D) in the body and through the feed screw,
hole B. The purpose of this is to enable the feed screw to be locked with a short
Tommy bar so that the screw (H1) that fastens the dial can be tightened.
Being put to use
Having completed the head I tested it out machining the bores in some gunmetal parts
for a small steam engine that I was making. This operation can be seen in Photograph
15. I am sure though that some viewers will rightly say this could have been more
easily bored with the part mounted on the faceplate, or in the four jaw chuck. This
I agree with, but I was searching for a job not only to prove the boring head, but
also to illustrate using a boring head on a lathe mounted milling head that I had
recently designed and made. This can be seen elsewhere on the web site.