Advanced Turning

Selecting a boring bar

Choosing the lead angle

Boring requires, like external turning, that the appropriate lead angle is determined by the application. When machining a through hole, an economical square insert with four cutting edges per insert can be used with a lead angle up to 90°. However, when facing to centre, boring bars with a large lead angle should be chosen to reduce cutting resistance.


Back boring, (cutting away from the workpiece) is a special machining method used only for boring. Back boring can be used when concentricity* of the outer and inner diameters is important, external turning and boring should be completed in a single set up. In this case, boring close to the chuck can be problematical, but with back boring type bars, machining without unclamping the workpiece is possible.


Click the links below to read more about different turning tools.

Image showing the lead angle when boring.

Lead angle