This chuck is made upon the same principle as the Warwick Drill
Chuck--namely, a flat spiral so acting on three jaws sliding in radial
grooves as to make them recede from the centre to admit any object
between certain sizes, and then to be tightened upon it. Fig. 1 is
a plan of a 4-inch chuck. Fig. 2 is a vertical section of the same.
Fig. 3 is a view of the outside of the chuck, and Fig. 4 is a separate
section of the principal part _a, a_, taken through the line _z, z_
(Fig. 1).
In Fig. 2, _a, a_ is this piece, _b, b_, has the spiral cut on it
which actuates the jaws 1, 2, 3 (Fig. 1), _c, c_ screws on the piece
_a, a_ to keep _b, b_ in its place and _d, d_ is the plate which
screws on the mandrel, and which is fixed to _c, c_, by three
countersunk screws, one of which is shown in section.
[Illustration: FIG. 1.]
[Illustration: FIG. 2.]
[Illustration: FIG. 3.]
[Illustration: FIG. 4.]
If the foregoing observations are carefully studied the further
practice of plain hand-turning in wood will not be difficult, and
we shall proceed to speak of metal turning, before passing to a
description of the Slide Rest and other apparatus usually added to
the lathe. We may, however, observe here, that, for ivory and hard
wood--especially the former, the first roughing down cannot be done
with the gouge. A point or small round-ended tool must in these cases
take its place, to be succeeded by one or more of those tools which
rather scrape than cut, as described in detailing the process of
hollowing out boxes and similar work.