Comparing the findings for the 20mm and 32mm bars is interesting as both
are almost the same length yet the deflection of the 20mm bar is considerably more.
This proving that it is predominantly the bar bending and not clearance in the lathe's
bearings that is the reason for the deflection that resulted.
Whilst the 20mm material was perhaps a borderline case but with anything smaller
it would be essential to set the steady adjacent to the chuck. From these examples
I hope the reader has realised the essential considerations when choosing which method
to use but it will not always be easy to decide. In this case, I can only say, if
in doubt err in favour of the method where the material is set to run true at the
point the steady is to be placed. I will continue with two examples of a steady's
use, one simple and one much less so.
Centring a bar.
If requiring to machine a part on the lathe whilst supported by the headstock and
tailstock centres, or just the tailstock centre, the part will need its ends centre
drilled. If, marking the end, centre punching then centre drilling, it is often not
easy to achieve the level of accuracy required. Even so, if accuracy is of limited
importance, standing a long part on the drilling machine for drilling can be a problem,
especially if one only has a bench drill having limited height between table and
chuck. The answer is to carry out the task on the lathe whilst supported by a fixed
steady, Photograph 3. This then being just a simple choice of which of the above
two methods to use.
Incidentally, it is worth considering that even if the steady is holding the bar
a little off the lathe's axis the bar will be still be running true about its own
axis at the point the steady is being used. Providing there is a little play in
the tailstock the drill will be pulled into a concentric position and to aid this
use the barrel almost fully extended for the task.
Designed for production
Now for something much more complex see Sk. 2.A which shows a shank and body for
a milling cutter chuck. The example also illustrates the need for the design of the
part being made having taken into consideration the method of manufacture. First,
the material would be set up in the four jaw and set to run true where the steady
is to be placed and the steady fitted and set. Then diameter A and the tapped hole
for the drawbar made.