I'd say you cannot afford to not use carbide inserts on this type of job. Anywhere from $8 to $12 per insert, perhaps 2 edges per insert, it makes for relatively inexpensive roughing. For the rough cut, the inserts need not be pristine, either, and the radius corner will withstand more abuse, and possibly even a touch up 're-chamfer' of the corner if it is slightly worn or chipped. It doesn't matter if all the inserts cut the same for roughing, because, well, it's roughing. ![Big Grin](images/smilies/biggrin.png)
That scale is tough on a sharp edged tool. I would recommend some brand of carbide insert mill, because inserts are commonly honed for roughing and will stand a bit of abuse. If you take the cut half width on the tool, the tool is coming down on top of the scale with very little rubbing action going on, and I think insert life will be decent. I often load up the tool with slightly used inserts for this type of rough cut, and stay near in case one blows up. Usually, carbide will give some warning with sparks being continuously generated when it is really about done for.
But, another way to try it would be helical interpolation, about 105% width of the tool. The stepdown depth can be lessened, but using the tool at full width reduces the banging effect of the cutter coming totally free of the work. If you go round in climb milling mode, the almost full width cut will have the cutting edge practically lifting the scale off from underneath. For helical interpolation, you will be making use of only the end flutes and a wee bit of the flute length.
It is possible to shorten a roughing endmill with a little bit of wear, and get 3 or 4 lives out of it. A skill well worth developing is re-gashing the end teeth, using a new endmill as a visual reference. While it is tricky to make the endmill centercutting, on a shallow ramp, only the perifery gets much use anyways. A concave grind while regashing the end teeth will suffice for a shallow ramp. Whatever you do, you must get the center 'dead zone' of the endmill away from the cutting plane. It'll glow red hot in no time if you don't.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)