Face milling

The 4 basic configurations

When an insert is located in a chip pocket of a face milling tool there are two main angles that need to be considered. One being the rake angle of the insert in relation to the tool centre, this is generally refered to as the radial rake angle (R.R). The other being the axial rake angle in relation to the axial direction and is generally refered to as the axial rake angle (A.R.). These angles can be either positive, negative or a combination of the two. There are four general combinations of these angles as can be seen in the table below.

 

Inserts used in the DP (Double Positive) and NP (Negative positive) combination need a form of relief to prevent rubbing with the workpiece, this means that positive type inserts are needed and therefore only one side can be used.

 

Inserts for the DN (double negative) combination do not need any relief and therefore negative inserts where both sides can be used. This makes the DN combination cost effective. The DN combination does not have high chip disposal properties but due to the economy factor they can be used on steels. Inserts used in the PN (Positive negative) combination have poor chip control and therefore only positive inserts can be used. There are no real advantages with the PN combination and it is usually not put to practical use.