Faced with turning a workpiece from square material the only choice for most will
be to use the four jaw chuck. If for a one off, or just a few then this may be acceptable
but for larger quantities, especially with smaller sections, using the four jaw can
be a chore. The idea for this project surfaced when faced with making around 100
2mm square nuts for a model cart. It is though worth considering for smaller quantities
and larger section bar.
Typically, if requiring to hold 6 mm square, then using a collet would be much better
than using the four jaw. Unfortunately though, collets for holding square material
are not available with some forms and expensive with others, and this article seeks
to overcome the problems by adding auxiliary jaws to a round collet. A set for holding
6mm square material in a 12mm collet is shown in Photograph 1, centre, together with
a set of a smaller size (right) and a partially finished set(left) with Photograph
2 showing the 6mm set in use.
Cut four pieces of square material and assemble with card packing as in Sk.1. The
size of material suggested enables a head to be made on the jaws preventing them
from entering fully into the round collet when in use.
With the assembly mounted in the four jaw and projecting by the chosen jaw length,
plus say 5 mm, the ends of the four pieces are faced level followed by machining
the outer diameter to a minimum diameter of 2mm greater than the round collet in
which they are to be used, and turning the required length to the collet diameter,
Photograph 3. Remove from the four jaw and set up the collet chuck and return the
jaws so as to turn the other end, Photograph 4, followed by parting off in the middle
to produce two sets. Whilst the one set is still in the collet face the end to produce
Next stage is to produce the required flats which can be done for small sizes by
filing, Photograph 5, or for larger sizes by milling Photograph 6.