Deep pocket, eh?
You could start out chain drilling the pocket. Hole drilling is often the fastest way to remove material. Or you could just pocket it down in layers. I kind of like the idea of at least doing the pocket corners with a twist drill, perhaps insetting them to leave room for a finish pass. Corners are where you hit maximum cutter engagement and would typically want to slow down on a job like this.
Whichever way you go, chip clearance is going to be key on this job. Make sure you have at least a strong air blast to clear out the chips running continuously.
For such a deep hole relative to cutter diameter, you want a carbide endmill. They're much stiffer. Take it easier on depth of cut too so as not to load it up to much with side forces.
Something else to consider is using the largest diameter endmill you can--they're stiffer. For a 3/4" wide pocket, you can sneak a 5/8" in there and it'll be stiffer than the 1/2".
How are you planning to program the pocket? Do you have a CAM program, or will you write g-code by hand?
Try to avoid full slot cutting as much as you can. Ramp down or spiral down and then just cut less than 1/2 the full tool diameter depth of cut as you move around the pocket.
G-Wizard comes up with the following feeds and speeds for 1/2" 2 flute carbide endmill:
- 4600 rpm
- 36 IPM
I would dial down the feedrate about 20% (that's a Hanita recommendation) since you're going deep, so maybe try 25-30 IPM.
If you can't use flood cool, be sure to get some WD-40 onto the cutter (to reduce chip welding) and go with the strong air blast.
Cheers,
BW
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