Cutting CornersPublished: 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:
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.