LATHE OPERATIONS - OD1645 - LESSON 1/TASK 2
2 Proper belt tension is obtained by loosening the cap screw and
pulling the motor firmly toward the operator. Do not over-tighten the belt,
as it reduces its life, and does not increase the capacity of the belt to
The belt is properly tensioned when the belt may be
deflected about an inch midway between the two sheaves.
(b) Shifting the Belt. The belt may be shifted from one set of steps to
another by pushing the motor forward or by tilting it upward, so as to
reduce the center distance between the sheaves.
(c) Alignment of the Belt. To obtain full power from the motor, it is
important that the belt run straight, thus preventing it from binding
against the sides of the V's. The steps of the sheaves should be in line,
allowing the belt to run without distortion.
If a belt does not run
straight, correct it by shifting either the motor sheave or the worm sheave
in or out along the spindle.
(d) Positioning for Angular Fork.
The normal position of the motor
spindle is parallel with the worm spindle. For angular adjustment with the
belt-driven heads, the motor is tilted to obtain parallelism with the head
To adjust the motor in the tilted position, loosen the two cap
screws on the motor mount bracket sufficiently to allow one cap screw to
slide in the curved slot. When the motor is positioned, these screws should
(e) Shifting Position of the Sheaves. Both the worm and motor sheaves
are held in position by two socket head set screws.
Both of these set
screws should be loosened before attempting to shift the position of the
1 If backlash develops, it may be removed either by eliminating the
end play of the lead screw in the cap, or by adjusting the fit up on the
lead screw bushing.
2 A threaded retainer collar is located inside the graduated collar
just below the ball crank handle. This threaded collar governs the