Boring, an operation that is too restricted to a lathed. Can be done easily in a milling machine. The offsret boring is an attachment that fits the milling machine spindle and permits most drilled holes to have a better finish and greater diameter accuracy.
Figure 4-21. Offset Boring head.
OFFSET BORING HEAD AND TOOLS
Figure 4-21 shows an offset boring head. Note that the boring bar can be ajusted at a right angle axis. This feature makes it posible to position the boring cutter accurately to bore holes of varying diameters.
This adjustment is more convenient than adjusting the cutter in the boring bar holder or changing the boring bar. Another advantage of the offset boring head is the fact that graduted micometer collar allows the tool to be moved accurately a specified amount usually in increments of (0.001) without the use of dial indicator or other measuring device.
NOTE : On some boring heads, the reading on the tool slide is a direct reading. On other boring heads, the tool slide advances twice the amount shown on the micrometer dial.