Advanced Turning
Insert types for boring
Insert geometry
Basically, the insert geometry should be chosen with the same parameters as for external turning. However, when boring, the tool overhang tends to be long and heavy machining is very difficult. Therefore, difference in clamping strength for different insert geometries does not have to be considered as much.
Click the links below to read more about different turning tools.
Effect of corner radius
Negative insert and wall interference
Effect of corner radius
Larger corner radii create higher back forces. The back force when machining with boring bars exerts in such a way as to try and bend the bar therefore care should be taken to prevent vibration. With smaller depths of cut, care should be taken because a larger insert corner radii reduces effective chip control or can change the direction of chip flow. A change in direction of the chip flow during boring is important because chips have to be discharged from the inside of workpieces to prevent chip jamming.
Negative insert and wall interference
When boring small diameters with negative inserts, the rake angle has to be made negative to avoid inside wall interference. (See image to the left).
This increases cutting resistance and can easily cause vibration, therefore positive inserts are usually used for boring. When boring larger diameters, it is possible to use negative inserts for improved economy.
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