FEEDS

Feed is usually measured in inches per minute. It is the revolutions per minute times the number of teeth in the cutter. Due to variations in cutter sizes, number of teeth, and revolutions per minute, all feed rates should be calculated from feed per tooth. Feed per tooth is the basis of ail feed rates per minute, whether the cutters are large or small. fine or coarse tooth, and are run at high or low peripheral speeds. Because feed per tooth affects chip thickness, it is a very important factor in cutter life.

Highest possible feed per tooth will usually give longer cutter life between grinds and greater production per grind. Excessive feeds may overload the cutter teeth and cause breakage or chipping of the cutting edges.

The following factors should be kept in mind when using the recommended starting feed per tooth.

Use lower feeds for:

Light finishing cuts
Frail set-ups
Hard to machine work materials
Frail and small cutters
Deep slots
Low tensile strength materials
Fine tooth cutters

Use higher feeds for:

Heavy, roughing cuts
Rigid set-ups
Easy to machine work materials
Rugged cutters
Slab milling cuts
High Tensile strength materials
Coarse tooth cutters
Abrasive materials

SEE CHART ON FEED AND SPEED

COOLANTS FOR CARBIDE END MILLS

Coolants can be used with end mills, but the cutter must get a continuous flow to avoid intermittent cooling and heating. This action is detrimental to the tool and in some materials will cause hard spots that will accelerate dullness of the end mill. Many end mill operations can be run dry or with and air blast for cooling. For machining aluminum a heavy flow of soluble oil and water or a strong air blast is recommended to dissipate the chips. Sulphur oils are not suggested because of their corrosive action.