LATHE OPERATIONS - OD1645 - LESSON 1/TASK 1
workpiece. The methods of operation described in this lesson are general in
nature.
With experience, the machinist will be able to vary certain
procedures with success for individual operations.
b. Setting Up the Lathe.
Before starting a lathe machining operation,
always ensure that the machine is set up for the job that is to be
accomplished. If the workpiece is to be mounted between centers, check the
alignment of the headstock center with the tailstock center (live or
deadcenter) and make the necessary changes as needed.
Ensure that the
toolholder and the cutter bit are set at the proper height and angle. Check
the workholding accessory to ensure that the workpiece is held securely.
Use the center rest or follower rest to support long workpieces.
(1) The first step in preparing the centers is to see that they are
accurately mounted in the headstock and tailstock spindles. The centers and
the tapered holes in which they are fitted must be perfectly clean. Chips
and dirt left on the contact surfaces will impair accuracy by preventing a
perfect fit of the bearing surfaces. Be sure that there are no burrs in the
spindle hole.
If burrs are found, they must be removed by carefully
scraping or reaming the surface with a Morse taper reamer.
Burrs will
produce the same inaccuracies as chips or dirt.
(2) Center points must be accurately finished to an included angle of 60.
Check the angle of the center with the use of a center gage. If the test
shows that the point is not perfect, true the point in the lathe by taking a
cut over the point with the compound rest set at 30.
The hardened
tailstock center must be annealed before it can be machined or set up in the
lathe and ground with the use of a toolpost grinder.
c.
Lathe Speeds and Feeds.
(1) General.
Determining the most advantageous feeds and speeds for a
particular lathe operation depends on numerous factors such as the kind of
material being worked on, the type of tool, the diameter and length of the
workpiece, the type of cut desired (rough or finished), the cutting oil
used, and the condition of the lathe being used.
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