Questions About Milling Steel W/8540

[Rootpass]

I came across an 8540 horizontal milling machine on Craig's list that was what I thought a pretty good deal. So I bought it and moved it to the basement.
My questions are related to milling steel. When I got it set up I played around with it using scrap aluminum and even some wood. After I was comfortable with the controls and felt that I had everything set up right, I tried milling a piece of steel. I don't have a pic of the steel but it leaves a beautiful finish on aluminum.
I'm guessing it's an rpm issue with the cutter (too slow) but it just seems that trying to cut steel is a bad idea.
I'm using a 4 1/2" diameter side cutting wheel. I'd guess I'd call it chatter even trying to take the lightest of cuts. Not sure if this make sense.
Any enlightenment would be great!
Thank you.

 

[Ulma Doctor]

is your cutter going the right direction, are you climb or conventional milling?
it you try to climb mill on a worn or light machine , you'll get nothing but frustration and poor finish.
conventional milling is the way to go here. the cutter will rotate opposite to feed.
cutting agents are also recommended for best finish.
in climb milling the feed and cutter rotation is the same direction, it takes a stout machine to climb mill effectively.
in addition, the 4-1/2" cutter should be turned slowly and feed rates are slow too for the best finish.
you can speed up a little more for roughing, but for finishing slow is best.

 

[T Bredehoft]

80 surface feet per minute puts your revolutions per minute at 68. That's pretty slow. You could feed.003 per tooth, with 36 teeth thats' under .100 inches per minute.

 

[Rootpass]

Ok that helps. I was using conventional milling while turning the cutter the proper direction with cutting oil.
You know with any other "regular" cutting tool( four flute mill bit, lathe tool etc) you can kinda tell what you might need to do to get different results. But using what amounts to what seems like a big circular saw blade on steel... It just feels unnatural.