R8 collet/Spindle

[ddickey]

Does the upper register portion of an R8 spindle have any function other than hold the collet so it is aligned for the drawbar?

 

[chips&more]

Both the taper and upper register are critical for proper alignment. The upper register controls solid angle error.

 

[MalR]

Does the upper register portion of an R8 spindle have any function other than hold the collet so it is aligned for the drawbar?

Oh yes: the short taper of an R8 collet is there to grip and drive the cutter but can’t cope with all the non-torque forces involved. Think of an end mill sticking out of the collet then imagine pressing on the tip of the cutter (this in one of the forces when taking a cut). The tapered part of the collet will act like a fulcrum. Without the parallel section of the mount the axis of the cutter could tilt in the direction of pressure on the tip.

Now imagine the cutter revolving: as each tooth contacts the work the pressure is applied. On cuts where only one tooth is in contact with the work at a time this leads to vibrational force which is also countered by the parallel part of the shank being as close a sliding fit as possible. Multi-tooth and spiral flute cutters help reduce but not eliminate this vibration.

If the parallel section of the R8 shank wasn’t there, accuracy and surface finish would suffer, not to mention wear and tear on the spindle.

Mal


Mal
AKA The Felsted Skiver

 

[ddickey]

Thanks guys.