Deep Pockets

Deep pockets are hard to machine. You’ve got tool rigidity problems with long tools to reach down deep coupled with chip clearance as the deeper the hole the harder it is to get the chips out of there. Couple that with thin walls and you have this part Eric Tate recently showed on the Yahoo Tormach forums:

3.125″ deep pocket, 3/8″ endmill, and thing walls too!

With a part like that, if the tool doesn’t chatter from the long reach the thin walls will want to.

Tate reports taking 0.030″ depth of cut passes and 600 rpm were the secret, discovered after some experimentation and a broken endmill. This is a perfect application for G-Wizard’s Cut Optimizer to use in determine how much depth of cut to take in a tricky low-rigidity situation like this. I plugged the numbers in for a 3/8″ carbide endmill cutting a full slot in 6061 aluminum with a tool reach of 3.5″ to give a little clearance from the tool holder when down 3.125″ in the pocket and G-Wizard Cut Optimizer came back with a suggested 0.026″ depth of cut. Pretty close to the 0.030″ that was determined experimentally.

Related posts:

1. Climb Milling a Must for Thin-Walled Parts
2. Deciding on Best Depth and Width of Cut When Milling
3. Interpolating Holes vs Twist Drills
4. Ballnose Surface Finishes
5. Why Do I Have to Know a Range of SFM’s and Chiploads?