Hi There,
Steve, as you surmise, the half-moon shaped
expanders (#23) fit in the angled slots of the
clutch shaft (the "screw #24") and when the
star knob (#37) is tightened, it pulls the two
expanders (#23) in and against the inside of
the shoes (#22). These in turn push against
the inside of the worm gear (#21).
It has been awhile since I have been inside an
apron but IIRC, the clutch pinion gear (#19)
has two square-like projections on one end.
These are the driving "dogs" of the clutch. The
shoes (#22) fit on either side of these dogs.
The coil spring (#20) pushes the inside of the
clutch pinion gear (#19) and against the cross
pin (#26) in the clutch shaft screw (#24). This
gives pressure (to open) in the clutch by pushing
the expanders (#23) away from the shoes (#22).
Remember, the worm gear (#21) is constantly
turning (so long as the leadscrew is turning). When
the clutch is disengaged, the clutch pinion gear (#19),
shoes (#22), expanders (#23), shaft (screw #24),
etc. are NOT turning with the worm gear (#21).
When the star knob (#37) is tightened, the clutch
shaft (#24) is pulled in. The expanders (#23) push
against the shoes (#22) and force them outward,
locking them with the worm gear (#21). These
shoes (#22) in turn are mechanically engaged with
the dogs on pinion gear (#19). So, with the clutch
engaged, the clutch pinion gear (#19) is locked with
the worm gear (#21) and in turn, will power the rest
of the apron (depending on the selector lever on the
apron).
The two pins (#26) are a later addition to the clutch.
Or maybe I should say, when the clutch shaft (screw
#24) was modified, the two pins (#26) became
necessary. Older versions of the clutch shaft (screw
#24) had 4 projections formed on the outside in two
pairs (and hence no pins were necessary). Their pur-
pose is to keep the clutch shaft and expanders co-
ordinated with the shoes and give something for the
coil spring (#20) can push against
Lastly, the "hair pin" spring (#25) is placed on the end
of the clutch shaft (#24) and the ends are "tucked in"
between the two expanders (#23). And the star knob
retaining screw (#30) is screwed on (left hand threads).
Good Luck!
-Blue Chips-
Webb