Figure 9-23.—Work mounted in a four-jaw chuck.rings, put each jaw the same distance from theoutside edge of the body of the chuck.2. Fasten the work in the chuck by turning theadjusting screw on jaw 1 and then on jaw 3, apair of jaws which are opposite each other. Next,tighten jaws 2 and 4.3. At this stage the work should be held in thejaws just tightly enough so it will not fall outof the chuck while you turn it.4. Revolve the spindle slowly by hand and, witha piece of chalk, mark the high spot (A in fig.9-23) on the work while it is revolving. Steadyyour hand on the tool post while holding thechalk.5. Stop the spindle. Locate the high spot on thework and move the high spot toward the centerof the chuck by releasing the jaw opposite thechalk mark and tightening the one nearest themark6. Sometimes the high spot on the work will belocated between adjacent jaws. In that case,loosen the two opposite jaws and tighten thejaws adjacent to the high spot.THREE-JAW UNIVERSAL CHUCK.—Thethree-jaw universal or scroll chuck is made so thatall jaws move at the same time. A universal chuckwill center almost exactly at the first clamping, butafter a long period of use may develop inaccuraciesof up to 0.010 inch in centering the work. You canusually correct the inaccuracy by inserting a pieceof paper or thin shim stock between the jaw and thework on the high side.When you chuck thin sections, be careful not toclamp the work too tightly because the work will distort.If you machine distorted work, the finished work willhave as many high spots as there are jaws, and the turnedsurface will not be true.Care of ChucksTo preserve the accuracy of a chuck, handle itcarefully and keep it clean and free from grit. NEVERforce a chuck jaw by using a pipe as an extension on thechuck wrench.Before mounting a chuck, remove the live centerand fill the hole with a rag to prevent chips and dirt fromgetting into the tapered hole of the spindle.Clean and oil the threads of the chuck and thespindle nose. Dirt or chips on the threads will notallow the chuck to run true when it is screwed upto the shoulder. Screw the chuck on carefully,tightening it just enough to make it difficult toremove. Never use mechanical power to install achuck.To remove a chuck, place a spanner wrench on thecollar of the chuck and strike a smart blow on the handleof the wrench with your hand. When you mount orremove a heavy chuck, lay a board across the bed waysto protect them; the board will support the chuck as youput it on or take it off.The comments on mounting and removing chucksalso apply to faceplates.Holding Work on a FaceplateA faceplate is used for mounting work that cannotbe chucked or turned between centers because of its sizeor shape.Work is secured to the faceplate by bolts, clamps, orany suitable clamping means. The holes and slots in thefaceplate are used for anchoring the holding bolts. Angleplates may be used to position the work at the desired9-15
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