28.3.2 Knurling Difficulties
If not done properly, knurling can destroy
the work. A common problem is the double-cut
knurl, Figure 28-14. It occurs when one wheel of
the knurl makes twice as many ridges as the
other. A double-cut knurl is usually caused by
one wheel being dull. Raising or lowering the
knurling tool to put more pressure on the dull
wheel often eliminates the trouble. Pivoting the
tool slightly to allow the right side of the wheels
to apply more pressure may also help.
Considerable side pressure is developed
during knurling operations. Watch the work care-
fully. Do not permit it to slip into the chuck or
become loose on the tailstock center. If a ball
bearing tailstock center is not used, keep the dead
center well lubricated.
Perform knurling before turning sections of a
shaft to smaller diameters. If knurling is done
after the smaller diameters are turned, the work
may spring away from the tool and produce a
very light knurl pattern. It may also produce a
permanent bend in the shaft, Figure 28-15.
28.4 FILING AND POLISHING
Lathe filing is done to remove burrs, round
off sharp edges, and finish off slight irregularities
on tapers. However, filing should only be done as
a last resort. A file is not intended to replace a
properly sharpened cutting tool and should not
be used to improve the surface finish on a turned
section. A properly set up lathe and a sharp
cutting tool will make filing unnecessary.
When filing is used to finish a job, stock
diameter should be left oversize by 0.002″ to
0.003″ (0.05 mm to 0.07 mm).
Chapter 28 Other Lathe Operations 453
Figure 28-11.
One type of knurling tool. (Armstrong Bros. Tool Co.)
Figure 28-12.
Knurl patterns. A—Diamond knurl pattern in coarse,
medium, and fine patterns. B—Straight knurl pattern
in coarse, medium, and fine patterns.
(J.H. Williams & Co.)
B
A
Feed
Avoid
Feed
Preferred
1″–
8
3
16
″
Figure 28-13.
Always start the knurl on the work.
A
B
Figure 28-14.
Knurl patterns. A—Correctly made diamond knurl
pattern. B—A double-cut diamond knurl. It results
when one knurl wheel is dull or the knurling tool is
slightly above or below center.