The variable stroke mechanism (5) as seen in photograph 19 could be replaced with
a single disk of steel having holes at different distances from the centre enabling
the ball race position to be modified and thereby the stroke length. Do note though
that there is no room above the ball race for the head of a fixing screw so the screw
would have to be fitted from the rear and with counterbored holes. The major disadvantage
of this suggestion is that the machine would then need to be partially dismantled
to permit the adjustment to be made. As the design is presented adjusting the stroke
length is very easy.
The other possible simplification is to mount the variable stoke mechanism onto a
mandrel that is mounted directly into the three jaw chuck eliminating the Input Drive
This would necessitate the machine being packed up on the lathe bed or the posts
increased in length. If this method was employed then the simplified variable stoke
mechanism would be a more practical proposition. For me, the disadvantage of the
arrangement is that it moves the machine back over the bed and into a less comfortable
operating position. Incidentally, the Input Drive Spindle is included in the design
as it is an essential item if being belt driven from a separate motor.
I subsequently decided to include a hold down feature to prevent the work lifting
and this starts on the next page.