I just got an order from shars, in which I ordered a 4-flute 7/8" roughing end mill but received its slightly cheaper cousin, the 5-flute version. I expect to use this for aluminum more than steel. Thoughts on whether I should complain and request replacement or suck it up?
In that size, a 5 flute will works fine in aluminum, I have one like that (actually mine is a 6 flute 7/8"). The nature of a rougher clears the chips, the chips will fly everywhere almost as fast as you can feed the material. Never had an issue with it loading up vs. conventional end mills.
Old bench top mill, loafing along milling 0.2" passes, 0.6 depth at 12 IPM at something like 2200 RPM climb milling. The chips are much finer than a standard 3 flute end mill. Using a standard end mill, 3 flutes is much preferred in aluminum for regular use. If you want the material removal of a rougher and the finish of a standard end mill, then you might look at a a 3 flute Minicut wave type endmill, like the 930 series. I have a few 1/2 and 3/4" ones that work very well. http://www.discount-tools.com/endmills/min-930.cfm http://www.discount-tools.com/endmills/min-930pm.cfm
You should notify Shars! Nothing gets fixed if no one lets them know there is a problem. Let them know also, that you want to keep what they sent, and are not asking for replacements. They may give you replacements anyway.