LATHE OPERATIONS - OD1645 - LESSON 1/TASK 2
that is too hard to cut by ordinary means or to machine work that requires a
very fine finish. It is known as either a toolpost grinding machine or a
toolpost grinder.
b.
Uses.
The toolpost grinding machine is a machine tool attachment
specially designed for cylindrical grinding operations on the lathe.
It
consists primarily of a 1/4 or 1/3 horsepower electric motor and a wheel
spindle connected by means of pulleys and a belt. The machine fastens to
the compound rest of the lathe with a T-slot bolt which fits into the T-slot
of the compound rest in the same manner as the lathe toolpost.
The toolpost grinding machine mounts grinding abrasive wheels ranging from
1/4 to 3 or 4 inches in diameter for internal and external grinding
operations.
The pulleys on the wheel spindle and motor shaft are
interchangeable to provide proper cutting speeds for the various wheel
sizes. The larger grinding abrasive wheels used for external grinding are
attached to the wheel spindle with an arbor. Small grinding wheels used for
internal grinding are fixed in a chuck which screws onto the wheel spindle.
The electric motor is connected to an electrical power source by means of a
cable and a plug. A switch is usually provided at the attachment to make it
easier to start and stop the motor.
c.
Operation.
(1) The toolpost grinder and grinding wheel takes the place of a lathe
cutting tool, in that it can perform most of the same operations as a
cutting tool.
Cylindrical, tapered, and internal surfaces can be ground
with the toolpost grinder.
Very small grinding wheels are mounted on
tapered shafts, known as quills, to grind internal surfaces. All toolpost
grinding must be performed with the grinding spindle center adjusted to the
exact height of the work center (figure 32 on the following page).
(2) The grinding wheel speed is changed by using various sizes of pulleys
on the motor and spindle shafts. An instruction plate on the grinder gives
both the diameter of the pulleys required to obtain a given speed and the
maximum safe speed for grinding wheels of various diameters.
Grinding
wheels are safe for operation at a speed just below
78
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