We at Cutting Tools Chicago aka General Cutting Tools along with Ingersoll Cutting Tools are going beyond the basics of finish milling to help you maximize the rigidity of your setup. Maximizing rididity will improve your end mill performance.
Deflection is produced by the cutting force on the tool. The tool’s length-to-diameter ratio determines the degree of effect cutting force has on the tool.
Deflection is directly proportional to L3 (length to the third power) and inversely proportional to D4 (diameter to the fourth power). In other words, deflection is radically reduced as diameter is increased and/or length is reduced.
Ingersoll has designed computer software to perform the many calculations required to determine the amount of deflection on the tool. Using Ingersoll’s “Rigidity Analysis” software, deflection for the following example can easily be determined:
Cutter: 2.000″ diameter, 4.00″ flute length,
No. 50 V-Flange adaption
Material: Low carbon steel
Speed: 400 SFM
Radial DOC: 1.00″
Axial DOC: 2.00″
Feed 12 IPM (.008 IPT)
The calculated theoretical deflection is .007″.
Deflection of .001″ or less is recommended for end milling operations. This example exceeds the desired maximum deflection of .001″. A cutter running under these conditions is likely to chatter, produce a poor surface finish, and exhibit reduced tool life.
The same example was recalculated after reducing the flute length from 4.00″ to 3.00″. Without making any other changes, the rigidity of the end mill improved dramatically. The theoretical deflection was reduced to .0009″.
By reducing the overall length-to-diameter ratio by 25 percent, deflection was reduced to less than half of the original example.
Many operational variables require additional rigidity. Among these are brittle cutting edge materials and any factor causing an increase in cutting forces such as negative cutting angles or tougher work piece materials.