First, relating to a Myford lathe only, I will comment on the diameter shown as “X”
on the drawing. This in theory needs to be a close fit within the bore through the
lathe's mandrel but I found on my lathe that the bore reduced over a short distance
being larger at the entrance and further into the bore passed the reduced diameter.
The body could be pushed passed this as the slits would allow it to reduce to enable
this but this would then necessitate the Stop Bar Holder being pushed in from the
chuck end, not really practical. There was therefore no option other than to make
the end a diameter that would go through the reduced portion. I have recollections
of having read that the split ring that secures the head adjustment can result in
the bore reducing. Whilst the outer end was made to a reduced diameter the short
length (4mm) next to 20mm diameter was made to fit the outer end of the bore.
Cut a piece of 20mm diameter just over 85mm in length and place in the chuck, face
end and turn the 16mm diameter by 15mm long section. Remove and return to the chuck
this time holding it on the diameter just turned leaving a gap of around 1mm between
the end of the jaws and the 20mm diameter, centre drill the end. Support with the
tailstock centre and turn diameter “X” over the 40mm length, smaller at the end if
required, see above. Reduce the central part of this to 12mm diameter as per the
Now skim the 20mm diameter just sufficient to ensure that it is concentric with the
other diameters turned and support this using the fixed steady. Remove the tailstock
centre and drill though about 9mm diameter followed by producing the tapered mouth,
Photograph 3, you can now return the top slide to its normal position.
With the deepest available boring tool produce the 10mm diameter, hopefully at least
50mm deep, at this point then there are now two options. The 10mm diameter can be
extended by drilling through with a 10mm drill, as I did, with the bored hole as
guidance or reversing in the chuck and opening up the bore from the other end, a
little over 10mm in diameter as concentric bores will of course not be possible.
As stated above I went down the 10mm drill route but this drilled marginally under
size and the Stop Bar Holder would not pass through. I then took a length of wooden
dowel sawed down this a short way and inserted a length of emery paper wrapping
this around it. This makeshift lap was then placed into the bore with the other end
in the drill chuck and the lathe started up and run for about ten seconds moving
the lap backward and forwards. After doing this a couple of times the Stop Bar Holder
entered with ease.