If just holding the material in the chuck to skim the outer diameter it will be necessary
to use a longer length of material so that the required length can be machined at
one pass. There will then be a short stub left in the chuck after parting off the
part to the required length. To avoid the possibility of two stubs that may not find
a use you could use a fixed steady to support a longer length. The part would then
be machined on the free end of the bar. For this approach see my pages on using lathe
Before proceeding with the parts for the boring head, make the tapping jig shown
in Sk. 1, ensuring that the bore is a close fit on the two parts just made. Only
the important dimensions are given on the sketch as other dimension can suit any
material that you have to hand. The purpose of this fixture will become apparent
as you read through the project.
Next cut a 76mm long length of 30mm for making the Body (1) and face one end. If
you require to use the reverse jaws in the three jaw chuck, then facing the end with
this level of projection should be avoided. Because of this, first centre drill the
end and support this with the tailstock centre. With this done it will be possible
to face the end knowing that the part will not be prised from the chuck. Reverse
the part in the chuck and repeat the process.
Cover the lower end with marking blue and scribe a line across this passing exactly
through the centre. Using a vernier height gauge and V blocks is the idea method.
Next mark out and drill and tap the two M4 holes (E), doing this 6mm deep at this
stage. Do note that the line scribed on the base will run in line with the bore eventually
to made and that the position of the holes are important relative to this. Next place
a patch of marking blue where the bore is eventually to be made and scribe a line
through this 15mm up from the base. Do this on the side that will have the 10mm diameter
The next stage is to mount the part on the faceplate for boring. Whilst the method
I propose will not be possible on a lathe smaller than 3 1/2" centres, it can easily
be overcome by making the body in two parts. I will describe this alternative construction
at the end of the article. Even so, the method of manufacture will still follow very
closely what I am about to describe.
Fix two fences on the faceplate as shown in Photograph 2. The important requirement
is that the fences are parallel and the centre line of the two pass exactly through
the lathe's centre. The distance between them however is relatively unimportant.
Working as in Sk. 2 will achieve this.