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SFM is a combination of diameter and the velocity of the material measured in feet-per-minute as the spindle of a milling machine or lathe. 1 SFM equals 0.00508 surface meter per second (meter per second, or m/s, is the SI unit of speed). The faster the spindle turns, and/or the larger the diameter, the higher the SFM.
A machinist calculator is a hand-held calculator programmed with built-in formulas making it easy and quick for machinists to establish speeds, feeds and time without guesswork or conversion charts. Formulas may include revolutions per minute (RPM), surface feet per minute (SFM), inches per minute (IPM), feed per tooth (FPT). A cut time (CT ...
The exact RPM is not always needed, a close approximation will work. For instance, a machinist may want to take the value of π {\displaystyle {\pi }} to be 3 if performing calculations by hand. R P M = C u t t i n g S p e e d × 12 π × D i a m e t e r {\displaystyle RPM={CuttingSpeed\times 12 \over \pi \times Diameter}}
20–40 fpm 0.10–0.20 m/s Bronze 150–240 psi ... = critical speed in RPM = smallest (root) diameter of the leadscrew in inches = length between bearing ...
Given a flow and head for a specific hydro site, and the RPM requirement of the generator, calculate the specific speed. The result is the main criteria for turbine selection or the starting point for analytical design of a new turbine. Once the desired specific speed is known, basic dimensions of the turbine parts can be easily calculated.
Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min −1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to 1 / 60 hertz .
Conversions between units in the metric system are defined by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre).
Peak torque is reached at higher rpm and is spread over a wider range of rpm. The specifications of these are known factors and can be designed to. Torque is a function of the length of the stroke, the shorter the stroke, the less available torque at lower rpm, but the piston velocity can be taken to much greater speeds, meaning higher engine rpm.