Page 48 - CITS - Fitter - Trade Theory
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FITTER - CITS



           LESSON 5 : Definition of cutting speed, spindle speed
                                (RPM), feed, depth of cut



           Objectives

           At the end of this lesson you shall be able to
           •  state the factors for determining the cutting speed
           •  determine RPM/spindle speed
           •  select RPM for drill sizes from tables



           Definition of cutting speed: Cutting speed is the speed at which the cutting edge passes over the material while
           cutting, and is expressed in metres per minute.
           Cutting speed is also sometimes stated as surface speed or peripheral speed. The selection of the recommended
           cutting speed for drilling depends on the materials to be drilled and the tool material. Tool manufacturers usually
           provide a table of cutting speeds required for different materials. The recommended cutting speeds for different
           materials are given in the Based on the cutting speed recommended, the r.p.m, at which a drill has to be driven

           Cutting speed calculation
           n – r.p.m

           v - Cutting speed in m/min.
           d - diameter of the drill in mm.
           p = 3.14
           Definition of RPM (Spindle speed)

           The term “RPM” stands for “Revolutions Per Minute,” and it is commonly used to measure the rotational speed
           of a spinning object, such as the spindle in machinery. The spindle speed, often expressed in RPM, is crucial in
           various industrial and manufacturing processes, especially in machining operations like milling and drilling.
           In machining, the spindle speed is a critical parameter that determines the cutting speed of a tool as it interacts
           with the workpiece. The appropriate spindle speed depends on factors such as the material being machined, the
           type of cutting tool, and the desired surface finish.
           Formula for spindle speed (RPM)
           (Cutting speed×1000)/(dp)

           Recommeded cutting speed

                                                              Materials being drilled (HSS Tool)

                         Aluminium                                                 70-100
                         Brass                                                     35-50
                         Bronze(phosphor)                                          20-35

                         Cast iron (grey)                                          25-401
                         Copper                                                    35-45
                         Steel (medium carbon/mild steel)                          20-30
                         Steel (alloy, high tensile)                               5-8

                         Thermosetting plastic (low speed due to abrasive properties)   20-30





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