Machinery's Handbook - 4: Cutting Speeds and Feeds

Machinery's Handbook - 4: Cutting Speeds and Feeds

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WARNING: Machine tools present a safety hazard. Improper operation can result in severe injury. These topics are for non-laboratory study only and are not to be used in conjunction with the operation of any tool or machine described herein. Never use a machine tool without the supervision of a qualified instructor.

Now the machining must begin.

What RPM should be used for a 3" diameter work piece?

What should be the feed rate?

A table in the Machinery's handbook gives RPM and Feed rate for 4130 steel with 380 BHN: Feed rate is shown to be .028 inches per revolution and speed is 240 feet per minute.

Note: Cutting Speed in surface speed per minute is often simply abbreviated as CS. So the CS of this metal* is 240.

To find the correct RPM the following formula can be applied:

RPM = (CSx4)/Dia. or (240 x 4)/3 = 320

Feed rate in inches per minute (instead of inches per revolution) can be found with this formula:

Feed=RPM x IPR where IPR is inches per revolution

Feed = 320 x .028 - 8.96 inches per minute.

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