Calculators
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SFM
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RPM
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IPR
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IPM
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IN3/MIN
Surface Speed (SFM)
Cutting speed at the tool from spindle RPM and diameter.
SFM = π × Dia × RPM ÷ 12Spindle Speed (RPM)
Required RPM from a target surface speed and diameter.
RPM = (12 × SFM) ÷ (π × Dia)Feed per Revolution (IPR)
Inches per revolution from feed rate and spindle speed.
IPR = IPM ÷ RPMFeed Rate (IPM)
Inches per minute from feed per rev and spindle speed.
IPM = IPR × RPMMaterial Removal Rate
Cubic inches of stock removed per minute in turning.
MRR = 12 × SFM × IPR × DOCSFM – a combination of diameter and the velocity (RPM) of the material measured in feet-per-minute as the spindle of a milling machine or lathe. 1 SFM equals 0.00508 m/s (meter per second, the SI unit of speed). The faster the spindle turns, and/or the larger the diameter, the higher the SFM.
RPM – The following equation is used to calculate spindle speed: rpm = sfm ÷ diameter × 3.82, where diameter is the cutting tool diameter or the part diameter on a lathe in inches, and 3.82 is a constant that comes from an algebraic simplification of the more complex formula: rpm = (sfm × 12) ÷ (diameter × π).
IPR – is the linear distance that the cutting edge travels during a single spindle rotation. In Milling and Drilling, it is a single rotation of the cutting tool. In Turning, Grooving, and Parting it a single rotation of the workpiece.
IPM – describes the rate at which a machine apparatus moves across a material (also known as the feed rate) and can be relevant to determining proper machine use as well as production rates for job quotes.
IN3/MIN – Similar to IPM but in 3 dimensions. Calculates how much material will be removed in cubic inches per minute.
