Figure 9-10.—Faceplate.tool so that the cutting edge is on the right side of thecutter bit and may be fed in toward the headstock.Inside-Threading Tool.—The inside-threadingtool (fig. 9-7, view J) has the same shape as thethreading tool in figure 9-7, view E, but it is usuallymuch smaller. Boring and inside-threading tools mayrequire larger relief angles when used in smalldiameter holes.LATHE CHUCKS.—The lathe chuck is a devicefor holding lathe work. It is mounted on the nose ofthe spindle. The work is held by jaws which can bemoved in radial slots toward the center of the chuckto clamp down on the sides of the work. These jawsare moved in and out by screws turned by a specialchuck wrench.The four-jaw independent lathe chuck, view A infigure 9-8, is the most practical chuck for general workThe four jaws are adjusted one at a time, making itpossible to hold work of various shapes and to adjust thecenter of the work to coincide with the axis of thespindle. The jaws are reversible.The three-jaw universal or scroll chuck, view B infigure 9-8, can be used only for holding round orhexagonal work All three jaws move in and out togetherin one operation and bring the work on centerautomatically. This chuck is easier to operate than thefour-jaw type, but, when its parts become worn, itsaccuracy in centering cannot be relied upon. Properlubrication and constant care are necessary to ensurereliability.The draw-in collet chuck is used to hold smallwork for machining in the lathe. It is the mostaccurate type of chuck made and is intended forprecision work. Figure 9-9 shows the partsassembled in place in the lathe spindle. The collet,which holds the work, is a split-cylinder with anoutside taper that fits into the tapered closingsleeve and screws into the threaded end of thehollow drawbar. As the handwheel is turnedclockwise, the drawbar is moved toward thehandwheel. This tightening up on the drawbar pullsthe collet back into the tapered sleeve, therebyclosing it firmly over the work and centering thework accurately and quickly. The size of the holein the collet determines the diameter of the workthe chuck can handle.FaceplatesThe faceplate is used for holding work that,because of its shape and dimensions, cannot be swungbetween centers or in a chuck. The T-slots and otheropenings on its surface provide convenient anchorsfor bolts and clamps used in securing the work to it.The faceplate is mounted on the nose of the spindle.(See fig. 9-10.)The driving plate is similar to a small faceplateand is used mainly for driving work that is heldbetween centers. The primary difference between afaceplate and a driving plate is that a faceplate has amachined face for precision mounting, while the faceof a driving plate is left rough. When a driving plateis used, the bent tail of a dog clamped to the work isinserted into a slot in the faceplate. This transmitsrotary motion to the work.9-7
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