Figure 9-6.—Knurling and threading toolholders.This arrangement permits feeding the tool to thework at any angle (determined by the angular setting ofthe swivel section). The graduated collars on thecrossfeed and compound rest feed screws read inthousandths of an inch for fine adjustment in regulatingthe depth of cut.Accessories and AttachmentsAccessories are the tools and equipment used inroutine lathe machining operations. Attachments arespecial fixtures that may be mounted on the lathe toexpand the use of the lathe to include taper cutting,milling, and grinding. Some of the common accessoriesand attachments are described in the followingparagraphs.TOOL POST.—The sole purpose of the tool post isto provide a rigid support for the tool. It is mounted inthe T-slot of the compound rest. A forged tool or atoolholder is inserted in the slot in the tool post. Bytightening a setscrew, you will firmly clamp the wholeunit in place with the tool in the desired position.TOOLHOLDERS—Some of the commontoolholders used in lathe work are illustrated in figure9-5. Notice the angles at which the tool bits are set in thevarious holders. These angles must be considered withrespect to the angles ground on the tools and the anglethat the toolholder is set with respect to the axis of thework.Two types of toolholders that differ slightly from thecommon toolholders are those used for threading andknurling. (See fig. 9-6.)The threading toolholder has a formed cutter whichneeds to be ground only on the top surface forsharpening. Since the thread form is accurately shapedFigure 9-7.—Lathe tools and their applications.over a large arc of the tool, as the surface is worn awayby grinding, the cutter can be rotated to the correctposition and secured by the setscrew.A knurling toolholder carries two knurled rollerswhich impress their patterns on the work as it revolves.The purpose of the knurling tool is to provide aroughened surface on round metal parts, such as knobs,to give a better grip in handling. The knurled rollerscome in a variety of patterns.ENGINE LATHE TOOLS.—Figure 9-7 shows themost popular shapes of ground lathe cutter bits and theirapplications. In the following paragraphs we willdiscuss each of the types shown.Left-Hand Turning Tool.—This tool is ground formachining work when it is fed from left to right, asindicated in figure 9-7, view A. The cutting edge is onthe right side of the tool, and the top of the tool slopesdown away from the cutting edge.9-5
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