452 Modern Metalworking
Figure 28-8.
Boring bars and toolholders. A—Interchangeable type permits the machinist to use the most rigid boring bar
for the job. B—Boring bar for light internal machining operations. C—Boring bar with interchangeable tool
ends. D—Heavy-duty boring bars. E—Clamp-type boring bar toolholder. (Armstrong Bros. Tool Co.)
F—Boring bar with indexable cutting tool inserts.
E
D
B
A
C
B
A
Figure 28-9.
Keep the cutting tool as close to the tool post as
possible for maximum support. A—Properly posi-
tioned boring bar. B—Boring bar projects too far
from the tool post. Vibration and chatter will
produce a roughly machined surface.
Figure 28-10.
The knurling operation.