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What is differential pitch in milling?

Tuesday, November 12, 2019

 

Differential pitch is the irregular distance between teeth within a milling cutter. This design cuts down vibration and reduces noise between the machine, tool and work-piece.

 

Ordinarily milling cutters have regular tooth spacing that is equally divided. However, to increase productivity, especially in shoulder milling operations, it is important to minimize the risks of chatter.

 

Scientific studies have shown that the stability of the milling operation improves when the spacing between the teeth is non-constant.

 

By why is this?

 

Vibrations develop due to dynamic interactions between the cutting tool and work-piece. This can occur on all, even the newest generation machine tools. Chatter may develop, even at very slow cutting speeds, which is commonly used to suppress vibrations in metal cutting.

 

Beside its negative affect on tool life is requires in general, additional operations which are mostly manual, are required to remove the chatter marks left on the surface. Therefore, chatter vibrations result in reduced productivity, increased cost and inconsistent product quality.

 

In order to have chatter free machining and improve material removal rates, high spindle speeds are utilized with regular pitch cutters. But this is not possible for many operations, as the required speeds may not be available on the machine tool being used by the customer.

 

Milling cutters with differential pitch offers significant improvements in stability when the speed is limited. Dormer Pramet’s new assortment of SSN11 cutters for high feed milling, for example, have this design feature included in its 40mm diameter range upwards. 

 

 

 

Willem Wittebol

Technical education manager

Dormer Pramet

 

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