Lathe guy needing endmill tips

[Azoth]

So 3 specific concerns.
Not talking aluminum. Say working with 25-30 hrc steel:

How much stock do you leave for finishing walls? Just a couple thou, or a certain percentage of tool diameter based on axial depth?

How do you calculate feed rates for surface roughness on faces and walls? On a lathe it's easy to calculate the surface geometry you will create based on tool nose radius and feedate, but the swirling bottom cutting action of the endmill (or facemills) make it more complicated. And my sidewall finishes don't follow the rules either (.004 IPR with a .5 radius lathe tool calculates to 1 RA, but a 1 inch endmill at .004 IPT clearly isn't that mirror-like since it leaves a distinct waviness presumably from tool vibration beating the part up.)

How do you handle an endmill breaking in corners? In this case, 44° included angle with a 3/4" - 5 flute endmill at 2" axial depth, .080" stepover. Do you speed up to reduce cutting forces or slow down to reduce chatter? Rough with a high feed mill and small step-downs instead and only ever load up the length of the endmill for finishing and never roughing?

 

[Cole2534]

1) I leave .010" - .020" based on the diameter of the final contour tool.

2) FSWizard

3) I avoid this by using a stock to leave parameter, as mentioned above, and then finish with a tool that has a radius smaller than the smallest corner radius.

 

[Azoth]

...
2) FSWizard

3) I avoid this by using a stock to leave parameter, as mentioned above, and then finish with a tool that has a radius smaller than the smallest corner radius.
.

2. I'm not seeing anything about feeds for Surface Roughness.

3. Okay so you want to swing through a corner with a G3 instead of driving the tool all the way in the corner? Although this is an open obtuse angle not a 90, but I suppose that's still where the tool broke even with only .0004 IPT after chip thinning.

 

[50BMG DUDE]

I think he is meaning to use an adaptive toolpath to pick out the corner in CAM. Hand coding corners like you are talking about suck. My best experience is to run a hog mill in and lie to the control so it leaves .005-.010. Then step down a finisher, the slower the RPM, the less the chatter. HSS tooling may be your friend here. It can take a lot more shock load than carbide and one good chip in a deep corner like you are talking about will destroy your cutting edges. In CAM you can tell the software how much of the diameter of the cutter to allow to engage the work. Hand coding you gotta do it manually.

Good Luck