Surface finish and nose radius

Surface finish and tool nose radius in turning – the connection

Turning shapes a helical groove on the part – a thread. The profundity of the groove is the roughness hight. The roughness hight (Rmax) is straightforwardly corresponding to the square of the feed rate, and inversely proportional to the nose radius of the tool. This condition gives you an unpleasant Ra value(the correct value is obviously just got by real measurement of the surface).

This table demonstrates the Rmax in microns for different combination of nose radius and feed rate. These are theoretical values, and the genuine vlue that you get will rely on upon the tool wear, the nature of the machine, vibrations, and so on. These qualities are however a decent beginning point.

To enhance the surface finish you can either reduce the feed rate or increase the nose radius.

Halving the feed rate enhances the surface complete four times (diminishes the Rmax value by 75 %).

Doubling the nose radius enhances the surface finish twice (lessens the Rmax value by 50 %).