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Cutting Corners

Published: 28/10/2016

When machining an internal corner radius on a CNC milling machine it is normally an advantage to use as large a cutter as possible. Therefore, if a component has an internal radius of 6mm the ideal cutter to use would be 12mm diameter (6mm radius). Unfortunately, when a cutter and internal radius are the same size chatter can occur due to the fact that for the brief moment the cutter is in the corner it has a lot of surface contact. This may mean that a 10mm cutter is chosen as a compromise.

If the internal radius size is an unimportant feature it is worth considering making the radius slightly larger than standard cutter sizes. On the example above a 6.5mm radius would allow a 12mm cutter to be used whilst reducing the risk of chatter.

Cutters are available in all sizes and some manufacturers have even started to supply under-sized cutters (e.g. 11.7mm diameter) to compensate for this problem, but using standard cutters is more economical. 

A list of standard sizes regularly used by us:

  • 1mm
  • 2mm
  • 3mm
  • 4mm
  • 6mm
  • 8mm
  • 10mm
  • 12mm
  • 16mm
  • 20mm

Generally, the larger the radius the easier and cheaper it is to produce.

Please feel free to call and speak to an engineer if you have any questions or comments.