Where large tool bits are required, the type of forged tool holder may be used. It provides a more
adequate method of clamping and supporting the tool than is provided by an ordinary tool post. The
tools used in such cases have a heavy shank of forged or hot-rolled bar stock in which a carbide tip is
brazed, thus reducing the amount of expensive tool material required.
Where several different operations on a lathe are performed repeatedly in sequence, the time required
for changing and setting tools may constitute as much as 50 per cent of the total time. As a
consequence, quick-change tool holders are being used increasingly. The individual tools, preset in
their holders, can be interchanged in the special tool post in a few seconds. With some systems a
second tool may be set in the tool post while a cut is being made with the first tool, and then be brought
into proper position by rotating the post.
In lathe work the nose of the tool should be set exactly at the same height as the axis of rotation of the
work. However, because any setting below the axis causes the work to tend to "climb" up on the tool,
most machinists set their tools a few thousandths of an inch above the axis, except for cutoff, threading,
and some facing operations, I ground all my tools to the general shape. On high speed bits I used only
about .010-nose radius, stoned on by hand. Set the tool up so it is about .010 above the tail stock
center. If I have the time, I usually use a feed of .004, but you will need to experiment to see which feed
works the best.
Usually I do not take over .020 passes per each side on each pass.
If I have the time, I usually use a feed of .004, but you will need to experiment to see which feed works
the best. Usually I do not take over .020 passes per each side on each pass.
What you have to watch for is that the Cut is not heavy enough that it will cause the barrel to spring,
especially on the barrel that is halfway turned down. This springing causes stress. Here is where a good