In FR = RPM × T × CL, what does T stand for?

In FR = RPM × T × CL, what does T stand for?

• A. Number of teeth on the cutter
• B. Time
• C. Torque
• D. Thickness

Answer: (A)

The main idea here is how feed rate in milling is built from three factors: how fast the spindle turns (RPM), how many teeth are cutting at once (the cutter’s tooth count), and how much material each tooth removes per pass (chip load per tooth). Each rotation the cutter with T teeth engages the work and removes a chip of CL thickness with every tooth, so the total material removed per revolution is T × CL. Multiply that by RPM to convert revolutions per minute into how far the tool advances per minute, which is the feed rate. So T represents the number of teeth on the cutter, not a time, a thickness, or torque. For example, with 6 teeth, a chip load of 0.01 inch per tooth, and 800 RPM, the feed rate would be 800 × 6 × 0.01 = 48 inches per minute. This makes it clear why increasing the number of teeth increases the feed rate, since more teeth remove material each revolution.

The main idea here is how feed rate in milling is built from three factors: how fast the spindle turns (RPM), how many teeth are cutting at once (the cutter’s tooth count), and how much material each tooth removes per pass (chip load per tooth). Each rotation the cutter with T teeth engages the work and removes a chip of CL thickness with every tooth, so the total material removed per revolution is T × CL. Multiply that by RPM to convert revolutions per minute into how far the tool advances per minute, which is the feed rate. So T represents the number of teeth on the cutter, not a time, a thickness, or torque.

For example, with 6 teeth, a chip load of 0.01 inch per tooth, and 800 RPM, the feed rate would be 800 × 6 × 0.01 = 48 inches per minute. This makes it clear why increasing the number of teeth increases the feed rate, since more teeth remove material each revolution.