The Driving Eccentric For The Automatic Mechanism; Timing The Sewing Hook - Pfaff 260 Service Manual

tigh~en
both set screws on the arm shaft bevel gear, hold the needle vibrating
eccentric bevel gear in proper engagement, and secure the transverse shaft
in its position by tightening the grub < s crew.
To check the above setting, note the following:
The needle vibrating eccentric is set correctly if, with dial A (Fig. 51) set on
"0" and the needle bar at its highest position, the latter makes no perceptible
sideways motion when finger-tip control F is depressed. For this purpose, the
needle position lever must be put in the central notch.
The Driving Eccentric for the Automatic Mechanism
This eccentric performs a dual function . On the one hand, it serves as a set
collar which bears against the arm shaft front bushing, and on the other, it
serves to drive the automatic em-
broidery mechanism.
To eliminate any end ploy, both the
needle bar crank and the driving ______
L
eccentric must be set as close to the
~--
__ _
1
_.
about
•1..-
(4 mm)
arm shaft front bushing as possible,
-~
leaving just enough play to permit
oil to enter the gap between these
parts. Take care, however, that the
arm shaft does not turn heavily.
Never attempt to make the arm
shaft run smoothly by tapping on
the balance wheeL This action is
likely to force the arm shaft front
bushing out of its mount and cause
binding of the parts at the needle-
bar end of the machine. When ad-
justing the end play of the arm
shaft, make sure a clearance of
.007", or 0.15 to 0.2 mm, is preserved
between the balance wheel bushing
and the arm shaft rear bushing.
Timing the Sewing Hook
Fig. 80
As the needle rises from the lowest point of its stroke, the needle thread
forms a loop on its short-groove side, near the eye, which is entered and en-
larged by the point of the sewing hook. The formation of this loop is the first
step in producing a stitch. With Pfaff 260 (-261) and 360 (-261) machines this
loop has reached the proper size when the needle bar has risen about
5 /6•",
or 2.0 mm, from the lowest point of i:ts stroke. This distance is termed "needle
bar rise". The correct amount of
nee~le
bar rise, naturally, can be set by trial-
48