Sherline Lathe User Guide and Specifications

holder that uses the P/N 7605 insert. This is a 55° insert good for turning, facing and
profiling. Also available are 80° inserts which are slightly less versatile but offer longer
tool life because of their stronger, more square shape. These tools should not be used to
cut hardened steels or piano wire. Materials such as those should be ground to shape, not
cut. Abrasive materials such as glass reinforced plastics can be easily cut with these tools.
FIGURE 18—3/8" Negative rake insert tool holder (P/N 7610).
Another tool available to Sherline machinists which holds carbide inserts is the 3/8" IC
55° negative rake insert tool holder (P/N 7610). The indexable carbide insert sits on the
tool holder at a 5° negative angle. This gives the sides of the cutter clearance even though
the insert has square sides. By having square sides, both top and bottom of the insert can
be used as cutting edges, giving a total of four cutting edges on each insert. Because of its
design, it cuts like a positive rake cutter which requires less rigidity than a negative rake
cutter. It gives you the best of both worlds—the four cutting edges of a negative rake tool
along with the lower stress loading of a positive rake cutter which is appropriate for a
lathe of this type.
FIGURE 19—Negative and Positive Rake Carbide Cutting Tips. Negative Rake tips can
be held upside down giving 4 cutting edges. Positive Rake tips cut from one side only, but
cut better.
When searching for a mirrorlike finish on copper or aluminum, a four-sided diamond
insert (P/N 7609) and a tool holder (P/N 7619) are also available. Though expensive, the
four cutting edges of the diamond insert mean you are really getting four tools in one,
making it a better deal than it may first appear.