High speed steel tools or carbide tools are used, the latter are appropriate for higher surface speeds, they offer no advantage at lower speeds.
High-speed steel tools should have high clearance angles of 10° to 15° and high positive back and side rake angles of 10° to 15° are recommended. Small clearance and relief angles should be avoided to reduce friction and heat build-up. Excessive rake and clearance angles can accelerate tool wear. Generous nose radii, sharp cutting edges and smooth tool faces improve surface finish. Raising the tool above centre and tilting it downwards may sometimes reduce problems of chatter in turning.
With carbide turning tool tips, which must always be rigidly supported, it is usually recommended that the end clearance should not exceed 6° to 8° and the top rake be within the range of +5 ° to +10 °. The approach angle may be from 10° to 20°, but is not of vital importance, sometimes being 45° or more. The end clearance angle is commonly from 15° to 20°. The nose of the tool is rounded to a maximum of 0.8mm radius. The angles given are varied somewhat, however, depending on the rigidity of the machine.
Speeds and Feeds
High speeds are preferred over high feed rates and depths of cut for roughing passes, to minimize heat generation. Cutting speeds of 60 to 90 m/min are recommended for high-speed steel cutting tools. Carbide tools are used with cutting speeds exceeding 180m/min. Feeds from 0.13mm to 1.6mm per revolution are used. Excellent surface finishes can be produced in low-feed passes.