What is a good rule of thumb for depth to diameter ratio for end mills used to make pockets?

There is no pat answer. It depends on the material, type of endmill, toothform and helix of endmill, application of coolant (dry, flood, mist, high pressure), and several other factors that immediately come to mind.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

+1 On Ornery's comments. Remember, deflection increases by the cube of the increase in length.

Hit submit early. Meant to say "for a cylinder. Flutes probably make it even worse"

Three or four diameters of extension from the collet face makes pocketing easy; no great worries about chip extraction or deflection.

Six diameters and up requires increasing levels of caution, reducing feed rate, depth of cut, stuff like that.

Recent fashion expedites deep pocketing by use of plunge cuts. I think you can do it even with non center-cutting cutters by orbiting the spindle as you plunge, kind of like thread whirling.



Mike Halloran
Pembroke Pines, FL, USA