maintained by locknuts (Fig. 7).

[Illustration: FIG. 7.]

But the screw cone system is not the only compensator used in sewing
machinery; where it cannot be easily introduced, other devices have been
employed.

The well known tapering needle bars of former years have been superseded by
cylindrical needle bars. The Wheeler & Wilson Company appear to be the
first who utilized the engineer's shifting box as an antifriction device
for round needle bars. They packed their bars round with felt rings, and
compressed the whole by a screw cap.

In the Singer machines the same excellent device has been adopted, hemp
packing and screw bushes being used (Fig. 8); _f_ and _g_ show the direct
action on the needle bar. This method of forming needle bar bearings,
partially of metal and partially of felt or hemp, has afforded the most
surprising results.

[Illustration: FIG. 8.]

When the bars are of hard or finely polished steel, no perceptible wear can
be detected in them, even after they have been in daily use in factories
for twelve months, whereas bars not so bushed might show considerable wear
in that space of time. The packing, to be effective, should be sufficiently
close to prevent as much as possible friction of the steel with the cast
iron needle bar ways. Lubrication of the steel is insured by keeping the
hemp packing moistened with oil.