Ball end mill question

First off, this is my third post on this forum in two days, and I apologize.
Anyway, I'm milling spiral flutes in a granite type tool steel, unhardened.
I'm using a 1/2", center cutting, 3 flute, coated carbide end mill. Applications engineer has me going full depth (.300" per side) in a single pass and my end mill is lasting exactly 1 part (about 48" total)
I'm getting some little chatter and curious if anyone here, who does milling more often than I, can give me any advice.. I'm a lathe guy, go easy on me lol


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You may have better luck with a 2 flute em. You may notice that on a 3 flute, only one flute crosses over the center. On a 2 flute, they both do.

That is a lot of depth for a tool that generally does not have much room for chip evacuation near the tip. I bet the groove looks like ass, too.

Consider taking a roughing cut with an endmill set at an approach of 45 degrees off centerline, giving the effect of machining a V notch down the centerline of the expected flute. Then, come in and clean that out with a 3/8" ball nose getting very close to the bottom of the groove (within a couple of thousandths) and then, the final cut with the 1/2".

HuFlungDung said:

That is a lot of depth for a tool that generally does not have much room for chip evacuation near the tip. I bet the groove looks like ass, too.

Consider taking a roughing cut with an endmill set at an approach of 45 degrees off centerline, giving the effect of machining a V notch down the centerline of the expected flute. Then, come in and clean that out with a 3/8" ball nose getting very close to the bottom of the groove (within a couple of thousandths) and then, the final cut with the 1/2".

Click to expand...

The flutes have a .200" offset from center. I'm finding faster speeds and feeds with high pressure coolant is getting good results now. Unfortunately, my cutting oil is getting so foamy after about 3 minutes that I have to stop about half way through to let it settle

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8strings8rounds said:

I'm getting some little chatter ...

Click to expand...

hi, try roughing with a short end mill, flat

with 1/2tool you may experience vibrations on most live tools

using a drill before the endmill will help a lot

raise Xoffset and run the program on all grooves
after that, lower Xoffset and run the program again
finally, use normalXoffset with a full radius tool and finish the part

on live tools, vibration is because the holder is not rigid, and not because it is bad, but simply thats the way it is; using tapered bearings is a solution

most live holder transmision have backlash, and not because of wear, but a lathe needs clearance between Mspindle inside the turret and live holder, otherwise it will grip when an index command is issued ... so google "Climb Milling, Conventional Milling, backlash" ; depends on turret type