Need Help!- Learning to HS machine A-2 steel (annealed)

[dylancw]

Hi all,

I own a high speed mill and am working on machining a cylindrical cavity 6" in diameter and 0.25" deep into a 12x12 piece of A-2 steel. I have a TiAlN coated solid carbide toric endmill, 1/2" in diameter that can machine say 1" deep. I have programmed the roughing path for a Vc of 1300 sfm, Fz of .002", stepover of .05", DOC of 0.0375". When I ran the path it looked like I was burnishing slightly, at lower feed override I had sparking. After say 200" along the path the carbide was starting to heat significantly (slight glow, some loss of tool coating observed after path was canceled). The mist oil/air coolant was turned on.

I tried varying feed and speed +/- 30% but it looks like I'm not even in the ballpark.

Do you have any recommendations for HS cutting annealed A2? I can't go lower than 3000 rpm with my spindle, max speed is 42k rpm (obviously not necessarily with a long holder and 1/2" cutter) and max feed is 840 ipm. Books, formulas, any ideas would be generously received.

Thanks,

Dylan

[JimBoyce]

Try a 3/16 stub end mill at 3000 RPM, which still may be too fast, and a feed rate of 0.0007 per flute. A Z depth of cut of .125" and 0.100 in the XY. Hopefully this is a good starting point.

[Andre' B]

Have not cut much soft A2 lately.

But gut feeling

I hope that end mill has about a 0.090 corner radius.
Try about 700 to 800 SFM
Get the feed rate up to about 0.006" per flute.
Step over about 0.25"
Doc down to about 0.008" to 0.010"

Look into some end mills designed for high feeds.
http://www.precisionsupply.com/docs/hanita_xfeed.pdf
There are others.

[dylancw]

Thanks to both of you. Andre, I think you are on to something. The endmill being used was a toric endmill with TiAlN coating, and the cutting angles on the tool are significantly steeper than on my 6-flute finish endmill.

We managed to get a stable cut at 3500 rpm, much shallower depth of cut (1% of diameter) and 120 ipm. But still some chatter (not significant heating though).

I think it's time to go endmill shopping. If anyone else here has preferred endmills for high speed roughing steel, let me know. I have no flood coolant and spindle taper is HSK-40E so no large insert tools. Thanks!

[jamesu229]

Watch the video on youtube titled 'high speed machining(really high)"
if this is the way you want to run, contact me.