Need Help!- Machining AR400 steel plate

[cybeeria]

I'm needing to machine several stepped pockets in some AR400 steel plate. It's on an already built unit so I can't substitute another steel. I don't do much machining on anything but aluminum, delrin, and the occasional mild steel or brass so I'm not too up on hard machining. I'm using an older Hurco KMB-1 that's in good shape but not real rigid and a max spindle speed of 3500 rpm. The mill has an AjaxCNC control upgrade and I use ONECNCXR3 software so I have high speed machining tool paths if that helps. The pockets I need to cut are about 1" by 2" and are stepped to .375 in depth. I assume that I need to use carbide cutters but I'm not real familiar with different coatings and what that means in terms of feeds and DOC vs RPM etc. I have a high speed spindle that I insert into my main spindle when I need very high speed for small aluminum jobs-about 40,000 rpm or so but I don't think that would work here.

I'm not in a big hurry so cutting speed is not my main concern.

Anyone have cutter recommendations? Coatings? Feeds etc.? Coolant or compressed air?

I am told that the "400" in the spec means a hardness of 400 Brinnell or about 43 Rockwell C.

Thanks in advance for the help!

Bill

[HuFlungDung]

Probably use a TiAlN coated carbide, maybe variable flute would be a nice option too. Maritool.com has a good selection at pretty good pricing...cheap enough that you won't feel too bad while learning

The High speed toolpaths are great for this type of slotting as it helps a lot when you can control the cutter engagement both to keep the horsepower requirement fairly constant, and also to cut cooler. You could probably get away with a 3/8 diameter tool and cut full depth of the pocket less a small finish amount. Machine dry with an air blast to get the chips out of the cut zone.

You could probably run your machine at its max rpm without hurting anything. Cut about 20% stepover amount in your toolpath settings. Feedrate about .005" per tooth or probably about 50 ipm on your machine. If it seems to jerk around too much, set your max high speed to a slower value like maybe 100 ipm as this affects how fast the machine loops around when the tool is out of the cut.

The occasional spark is okay when the tool is cutting.

[cybeeria]

Thanks very much. I have ordered the tools you described and will give them a try in the manner you suggest.

Bill