Before you attempt to make the item illustrated in this project it is essential that
the lathe is set up to turn parallel. For this, I would suggest at least to within
0.002mm over a distance of 100mm, certainly no more than 0.005mm. More than that
and the subject of this project will not be as accurate as its uses demand, this
being a cylindrical square. If your lathe is outside this value then do view my pages
on setting a lathe to turn parallel before proceeding. In any case, the pages may
be worth reading as the information may enable you to improve the situation even
beyond the values I quote above.
With the lathe now turning parallel it is time to make the Cylindrical Square, to
be precise you need to make two, the reasons becoming known later. However, you
think it is a bit of a gimmick, then it is worth noting that one 150mm high and 100mm
diameter is likely to set you back a very large sum of money, it is of course hardened
and ground to a very high standard of accuracy and is used in industry as a reference
for inspection work. In the home workshop cruder versions can be used for a number
of reasons but more about that later.
Mount in the three jaw chuck a length of steel, I would suggest a minimum of 2 times
the width of the tee slots in your milling machine and 100mm projecting from the
chuck, centre drilling the end ready for supporting with the tailstock centre. With
this done face the end, and recess it with the tool set at an angle doing this as
close to the tailstock centre as is possible. Sk. 1. I use a home made half centre
in the drill chuck, as shown in Photograph. 1, enabling facing to be achieved completely
to the drilled centre.
Next drill to a depth of say 90mm, no more, using a drill large enough to accept
the studs you use on your milling machine table. If your drill is not long enough
then drill to the deepest possible
Now turn the outside diameter using a finely honed knife tool, ensure this has a
small flat on the end, so as to obtain a fine finish, Sk. 2 illustrates. Turning
the outside diameter will have to be done without the tailstock centre engaged, so
take only light cuts, 0.2mm initially, finally 0.05mm. Measure the part along its
length using a micrometer and if parallel, at least better than 0.005mm over 100mm,
continue reducing the diameter until a convenient value results, say 24mm if made
from 25mm bar. Whilst diameter is not vitally important an accurate value may be
of help if using it where it becomes part of the measurement being taken.