Best way to cut a 7.5 slot x 35mm

[komatias]

Hmm this is a difficult one.

What CAM package are you using to do the motion? Trochoidal motion is a roughing operation and it leaves jagged edges on the walls or you pocket or slot. It thus needs a finishing pass.

7.3mm will leave you 0.1mm per side to finish and at a depth of 35mm that can be pretty sketchy. Ideally you would do trochoidal in this trench (not slot) with a 5mm endmill, 6 would be very tight. So 5mm endmill sticking out at least 40mm is pretty flexible at the tip. And 3000rpm is a bit limiting.

To do this job I would actually go with conventional milling, slotting back and forth with a 6mm endmill, or even a 1/4" one (6.35mm). Again the stick out length will become critical. For best results on such deep slots, make the sides of the roughed slot slightly tapered and do multiple light finishing passes. So for example you start the slot at 7.3mm wide at the top and gradually go to 6.8mm wide at the bottom. This will give your endmill an easier time in the finishing operations.

In terms of speed, go at full wack and feed will depend on your endmills capability. use the free FSwizard http://zero-divide.net/index.php?page=FSWizard_SA

Regards

George

[magicniner]

I'd use a 6mm tool and a ramped internal profiling strategy, by keeping the cutting depth small but constant you can cut deep slots and hold the dimensions as well at the bottom as the top and use a very fine finishing cut if required just to clean things up.

+1 on Zero Divide's HSM Advisor

[hoezap]

Thank you very much indeed to both of you