Lathe Operations: Facing

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Facing Operations Facing is the process of removing metal from the end of a workpiece to produce a flat surface. Most often, the workpiece is cylindrical, but using a 4-jaw chuck you can face rectangular or odd-shaped work to form cubes and other non-cylindrical shapes.

When a lathe cutting tool removes metal it applies considerable tangential (i.e. lateral or sideways) force to the workpiece. To safely perform a facing operation the end of the workpiece must be positioned close to the jaws of the chuck. The workpiece should not extend more than 2-3 times its diameter from the chuck jaws unless a steady rest is used to support the free end. Cutting Speeds

If you read many books on machining you will find a lot of information about the correct cutting speed for the movement of the cutting tool in relation to the workpiece. You must consider the rotational speed of the workpiece and the movement of the tool relative to the workpiece. Basically, the softer the metal the faster the cutting. D…

Machines Used Sheet Metal Workshop

When a large number of jobs are made, particularly with heavy gauge sheets, hand operations like bending, swaging and rolling are difficult, time consuming and uneconomical. To cope up with this problem, both hand and power operated sheet metal machines are developed. Some of these machines are described in the following paragraphs.



Cramp Folding Machine



This machine is used for folding or bending thin gauge sheet metal at different angles up to 1350. Bending arms can be adjusted accordingly, when bending sheet metal of different thickness. Slots in the bending arms are provided to accommodate small cramps or wired edge while bending. Capacity of this machine is 36" x 16 SWG (1.6mm). Thick gauges should not be bent in this machine. From time to time, it should be oiled and maintained properly.



Metal Roller or Bending Roller 



It is used for shaping sheet metals into cylindrical jobs. Sometimes this machine is used for straightening the bent or buckled sheet metals. It is also used for breaking-in the sheet metal when shaping into conical shape or frustum of a cone. Grooves are provided on one of its end for accommodating wired edges. The rollers are adjusted to the radius of the job and shape. Alignment of the bending rollers can be obtained by adjusting the wing nuts. It is classified by the length and diameter of its rollers. These are either hand operated or power operated.



Swaging Machine



This machine is also known as Beading Machine. It is used for forming swages or grooves on jobs made out of thin gauges sheets to induce strength. This machine is available in different ranges to form swages at a desired distances. The swaging wheels are interchangeable in sets of two for varying grooves. These machines are supplied with different heads in varying sizes ranging from 2 ½" to 18". It has a capacity of swaging 18 SWG (1.2mm) sheet metal. The sheet is clamped in between the rollers at the pre-determined position and guidance along the line is obtained by resting the edge of the sheet against the slideable guide.



Jenny Machine



It is a portable machine, generally held in vice or mandrel. It is available in various sizes and used for turning over the edges of round disc and also for setting the edges of sheet metal around the wired edges. It is also used for flanging the round disc prior to bending or turning over a round disc. It is classified by the diameter of the rollers.



Hilmour Tube Bending Machine



Tube bending machine is used for bending metal tubing. When bending thin tube of larger diameter, there is possibility that the wall of metal tube may collapse or ripple. To overcome these faults the tube bending machines are designed.



Description



There are two types of bending machines used in service, namely A2 type for bending tube up to 7/8" in diameter, the large machine `C’ type for tube sizes from 1" to 2" in diameter. The two types works on the same principle, the major difference being that the operating leaver of ‘C’ type is moved by a ratchet arm and pinion working on circular rack, which is mounted on a heavy cast iron base. A2 type is described in the following paragraph.



This machine can be secured by bolts to the bench or the underside of its base plate may be gripped in a vice. Alternatively, the hollow square leg provided underside of the base might be held in a vice.



The machine is provided with grooved formers and guides of different diameters. The purpose of grooved formers is to receive different diameters of tubing and purpose of guide which exactly fits the tube and former, is to force the tube round the former and avoid damage to the tube.



Panning or Stepping Machine



It is fixed on a working bench and used for the purpose of joggling the straight sheet, cylindrical jobs and discs.

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