Prepared By: Gp Capt Dr. Hamid Ullah Khan Niazi Lathe Operations : Lathe tool, Facing, Turning, Knurling Grooving and Form turning Prepared By: Gp Capt Dr. Hamid Ullah Khan Niazi
Learning Objectives After completing this unit you will be able to: Use the nomenclature of a cutting-tool point. Describe the cutting action of different types of machines. Identify the applications of cutting tools in different operations such as Facing, turning, Knurling, Grooving etc.
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Facing 30 Workpieces to be machined are generally cut a little longer than required and then end-faced to the proper length. Facing is an operation of machining the ends of a workpiece square with its axis. Work is often held in a chuck, faced to length. The purposes of facing are: To provide a true, flat surface, square with the axis of the work To provide an accurate surface from which to take measurements To cut the work to the required length Note: For facing the tools post is given an angle (30 deg) with the axis vertical to the axis of WP rotation. When facing, finishing cuts should begin at the center of the workpiece and feed toward the outside.
Parallel Turning Work is generally machined on a lathe for two reasons: to cut it to size and to produce a true diameter. Many factors determine the amount of material that can be removed on a lathe at one time. Whenever possible, a diameter should be cut to size in two cuts: a roughing cut and a finishing cut Note: To remove metal from a cylindrical piece of work and have the same diameter at each end, the lathe centers must be in line. (See Unit 49 for the methods of aligning centers.) Before either the rough or finish cutis taken, the cutting tool must be set accurately for the depth of cut desired.
Filing in a Lathe Work should be filed in a lathe only to remove a small amount of stock, remove burrs, or round off sharp corners. When larger amounts must be removed, the work should be machined because excessive filing will produce work that is out of round and not parallel. Filing with the left hand is recommends, so that the arms and hands can be kept clear of the revolving chuck or driveplate. Always remove the toolbit from the tool-holder before filing, unless the machining operation doesnot permit it. In this case, move the carriage so that the toolbit is as far as possible from the area being filed. Note: Before attempting to file or polish in a lathe, cover the lathe bed with a piece of paper to prevent filings from getting into the slides and causing excessive wear and damage to the lathe. Cloth is not suitable for this purpose because it tends to get caught in the revolving work or the lathe.
Polishing in a Lathe After the work surface has been filed, the finish may be improved by polishing with abrasive cloth.
Turning to a Shoulder When turning more than one diameter on a piece of work, the change in diameters, or step, is known as a shoulder. Three common types of shoulders are illustrated in Fig above.
Knurling Knurling is a process of impressing a diamond-shaped or straight-line pattern into the surface of the workpiece to improve its appearance or to provide a better gripping surface. Straight knurling is often used to increase the workpiece diameter when a press fit is required. Diamond- and straight-pattern rolls are available in three styles: fine, medium, and coarse The knurling tool is a tool- post-type toolholder on which a pair of hardened-steel rolls are mounted. These rolls may be obtained in diamond and straight-line patterns and in coarse, medium, and fine pitches. Some knurling tools are made with the three various pitched rollers on one holder
The universal knurling tool system consists of a dovetailed shank and as many as seven interchangeable knurling heads that can produce a wide range of knurling patterns. This tooling system combines versatility, rigidity, ease of handling, and simplicity in one tool
Grooving Grooving, commonly called recessing, undercutting, or necking, is often done at the end of a thread to permit full travel of the nut up to a shoulder or at the edge of a shoulder to ensure a proper fit of mating parts. Grooves are generally square, round, or V-shaped Rounded grooves are usually used where there is a strain on the part and where a square corner would lead to fracturing of the metal at this point.
Form Turning on a Lathe It is often necessary to form irregular shapes or contours on a workpiece. Form turning may be done on a lathe by four methods: Freehand Form-turning tool Spherical tool Hydraulic tracer attachment
Hydraulic Tracer Attachment
Summary This unit helps in understanding different cutting operations which are performed in shaping and designing any work piece. Set up and use knurling tools to produce diamond shaped or straight patterns on diameters. Machine convex or concave forms on diameters free hand. Use of hydraulic tracer attachment
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