Engine Lathe Operations and Controls - 8: Setting Speeds and Feeds 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. To machine various types of materials, hold tight tolerances and produce good surface finish , the spindle RPM must be properly selected. Selection of spindle speed is accomplished by manipulating the appropriate levers. Speeds are calculated by formulas. It is important for the operator to know the horsepower of the lathe's motor to select speeds and feeds within the machine's limits. Nearly every gear head engine lathes use a method similar to this video for setting spindle speeds. First you will have to locate the spindle speed read out on the machine. Now select an RPM from those available. In the video 370 RPM is selected which requires the two levers shown to be in the correct position. The next speed selected is 36 RPM. As with spindle speeds, correct feed rates must also be calculated. Feed rates can be set by locating the settings panel (index plate) on the lathe. In this video 0.002 per revolution is selected. Four levers and one dial must be set to A E V 3 X. The next feed rate selected is 0.040 per revolution which requires a setting of B E R 7 X. Both feedrates were with the same spindle RPM. Changing spindle RPM does not change the feed rate. The correct RPM is calculated from a known cutting speed (CS) in Feet Per Minute (FPM). The CRS is dependent on he material and should be looked up in the Machinery's Handbook. The formula is RPM = (CSx4)/diameter. Typical CS for aluminum is 250 and for mild steel it is 80. Therefore a 6" dia bar of mild steel should be turned at (80x4)/6= 53 RPM. The correct feed rate in Inches Per Revolution (IPR) is calculated from chipload. Chipload is the amount the cutter is buried into the part and varies from tool to tool. R.S. Do not confuse feed "speed" with feed "rate". Feed rate is the amount the tool moves for each revolution of the spindle. If the spindle is turning very slowly the tool feed speed will be slow. If the spindle is turning very fast the tool feed speed will be very fast. In both cases the tool feed rate is identical. R.S. label: lathe operating, contorls, functions, parts, movements, ways, motor, headstock, spindle, brake, speeds and feeds, carraige, tailstock, centers, faceblate, dogs, threading, staedy rest, follower rest, lathe sizes, taper attachment