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 rigidity will improve your end mill performance.
Rotary Tool Holder: Most end mills are run in rotary tool holders which connect the tool to the spindle. Ironically, due to the added length and extra joint, this is the least rigid of all end mill adaptations. To maximize rigidity with this adaption, an end mill with the largest diameter shank and the shortest adapter possible should be used.
Integral Shank: An improvement over the straight shank adaption is an integral shank. This eliminates the joints required with rotary tool holders and greatly improves length-to-diameter ratios. Many standard Ingersoll end mills are available with No. 50 taper adapters. Other tapers are available upon request.
No. 50 tapers have a standard .125″ gap between the flange and spindle face. To eliminate the gap, many Ingersoll machines have a simultaneous fit adapter designed to be used in conjunction with a precision spindle face. Because the adapter flange has bearing on the spindle face, the joint is more rigid.
Flat Back Drive: Another way to eliminate the .125″ gap is to use a flat back drive system. It consists of a centering plug with a pilot diameter on the spindle. The end mill is bolted directly to the spindle face. This adaption is often used for large, heavy-duty end mill operations requiring maximum rigidity.