Facing is done to obtain a flat surface on the end of cylindrical workpieces or on the face of parts clamped in a chuck or face plate (Figures I-143 and I-144).The work most often is held in a three- or four-jaw chuck.If the chuck is to be removed from the lathe spindle, a lathe board must first be placed on the ways.Figure I-145 shows a camlock-mounted chuck being removed. The correct procedure for installing a chuck on a camlock spindle nose is shown in Figures I-146 to I-151.The cams should be tightly snugged (Figure I-151) for one or two revolutions around the spindle.
Setting up work in an independent chuck is simple,but mastering the setup procedures takes practice. Round stock can be set up by using a dial indicator (Figure I-152). Square or rectangular stock can be set up either with a dial indicator or by using toolholder turned backward (Figures I-153 and I-154).
Begin the setup by aligning two opposite jaws with the same concentric ring marked in the face of the chuck while the jaws are near the workpiece. This will roughly center the work. Set up the other two jaws with a concentric ring also when they are near the work. Next, bring all the jaws firmly against the work. When you are using the dial indicator,zero the bezel at the lowest reading. Then, rotate the chuck to the opposite jaw with the high reading and tighten it half the amount of the runout. It may be necessary to loosen the jaw on the low side slightly. Always tighten the jaws at the position where the dial indicator contacts the work, because any other location will give erroneous readings.
When you are using the back of the toolholder,the micrometer dial on the cross slide will show the difference in runout. Chalk is sometimes used for setting up rough castings and other work too irregular to be measured with a dial indicator. Workpieces can be chucked either normally, internally, or externally (Figures I-155 to I-157).