In internal profiling, the tool is exposed to both radial and tangential cutting forces. The radial cutting forces will deflect the tool away from the workpiece and the tangential forces will force the tool downwards and away from the centre line.
When boring small-diameter holes, it is particularly important that the clearance angle of the insert is high enough to avoid contact between tool and wall of hole.
In profile turning the cut can vary as cutting depth, feed and speed. The largest suitable nose angle on the insert should be selected for strength, cost efficiency and accessibility. The most frequently used nose angles are 55° and 35°.
Entering angle and insert nose radius are both important factors for accessibility. The workpiece profile has to be analyzed in order to select the most suitable copying angle.
A free cutting angle of at least 2° between workpiece and insert has to be maintained. However, for reasons of surface finish and tool life, at least 7° is recommended.
First choice is a tool with 93° entering angle (-3° lead angle) and a D-style (55°) insert. If a larger ramping angle is needed, use a V-style (35°) insert.
For the possibility to profile the face or to make a corner relief, choose a holder with a 107–117° entering angle (-17 to -27° lead angle).
There are specific tools for back boring, especially designed to machine a shoulder in the opposite direction