Milling

The theory is that two-flute mills are best used for steel and four-flute for aluminum.   I have been trying to edge mill steel.  The two-flute rough 3/4" mill has been far less effective than my four-flute 3/8" finish mill.

I find myself wondering if rough finish is less effective at edge milling than a finish mill or perhaps my coarse two-flute mill is dull.  How do you measure that? Or should I just buy another 2-flute mill and see how it works?

UPDATE: It was just simpler to buy some 1" x 1" x 1/8" thick angle aluminum.  The mill rapidly reduce these to .5" x 1" x 1/8" clamps.  Steel is really hard for a Sherline to mill, it seems.  

The three motors on the mill are old.  The first CNC mill I bought wore out.  When I asked Sherline to repair it they said it was beyond repair, but offered me a blem version for 20% off, using my old motors. When it arrived, I emailed them, "Cosmetic defects are missing.  Ship them at once."  All of this to say, one of the motors seemed to have developed some sort of stepper motor confusion.  When I swapped the X and Z motors, the problem went away, so I ordered one of the new high-torque motors.  We are about to pay our income taxes so I will wait a few weeks to order the other two.