Let's say you're using a single-flute endmill to machine a piece of 6061 aluminum. There are numerous jobs you can accomplish with this tool, but each will have a different feed for a different reason.

Slow Feed Rates

Slow is 60 ipm for finishing. If you need an exceptional quality in the finish of a floor or wall, it helps to slow the machine down to take a fine chip and decrease cutter load/cutter deflection.

Medium Feed Rates

Medium is 120 ipm for slotting. Something a single flute does particularly well is slotting, which is a toolpath that has 100 percent of the tool diameter engaged in the material. Using a proper depth cut (25 percent of tool diameter), you can cruise along at a decent pace without worrying about clogging up on chips.

Fast Feed Rates

Fast is 180 ipm for traditional roughing. When you are using a normal milling strategy, in the range of 33-50 percent depth of cut (2-3mm) with a 50-70 percent stepover, you can be fairly safe kicking the speed up, just keep an eye on your spindle load.

Very Fast Feed Rates

Very fast is 240 ipm for trochoidal roughing. If you are using Mastercam (Dynamic milling) or Fusion 360 (Adaptive clearing), you may have heard of this strategy before. Instead of going about the traditional method, this method utilizes more of the flute to boost efficiency. For instance, we could use 100-200 percent depth of cut (6-12mm) with this strategy because our stepover would be decreased to 10-20 percent. In many cases, this prolongs the life of the tool and puts less strain on the spindle, so you can safely bump the feed rate up.

Extremely Fast Feed Rates

Extremely fast is 300 ipm for shallow roughing. If you are taking off less than 10 percent depth of cut (0.60mm), then you should be safe cranking the feed way up. With such a shallow cut, you won't have to worry about overloading the tool or spindle.