Lathe Operations: Facing

Image
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…

Sheet Metal Thickness Measurement

Many engineering components are produced from a sheet of metal, which is cut to shape and then folded to form the finished article. The edges are then secured by various methods such as welding, brazing, soldering, riveting etc.



The term ‘sheet metal’ is normally used to describe metal sheets with a maximum thickness of 2mm. Above this thickness, it is usual to use the term ‘plate’. The sheets of very low thickness (30 to 50 SWG) are known as foils.



The thickness of metal sheets is identified by a series of numbers, known as Standard Wire Gauge (SWG). Table 1 below lists the SWG numbers and the corresponding thickness or diameter of wire in mm. Table 2 gives the frequently used SWG numbers and their thickness in mm.



Table 1 - SWG Number & Corresponding Sheet Thickness or Wire Diameter

























































































































































SWGMMSWGMM
7/012.700142.032
6/011.786151.828
5/010.973161.626
4/010.160171.422
3/09.449181.219
2/08.839191.016
08.230200.914
17.620210.813
27.010220.711
36.401230.610
45.893240.559
55.358250.508
64.877260.457
74.470270.4166
84.064280.3760
93.658300.3454
103.251350.2134
112.946400.1219
122.642450.0713
132.337500.0254




Table 2 - Most frequently used Standard Wire Gauge














































SWG(Number)Thickness in MM (Approx.)
103.2
122.6
142.0
161.6
181.2
191.0
200.9
220.7
240.6




It may be noted that:



(a) Maximum SWG number is 7/0 = 12.70 mm and minimum SWG number is 50 = 0.0254 mm



(b) 1 SWG = 7.620 mm



(c) Higher the SWG number of a sheet, the lesser will be its thickness.



(d) Lower the SWG number, higher the thickness of the sheet.



Standard Wire Gauge (SWG)



The thickness of the sheet is measured with the help of a standard wire gauge shown in image below. The sheet is put in a suitable slot and SWG number is noted. It is then put in one slot below this test slot and one slot above this test slot. If the grips in these two slots are very tight and loose respectively, then the SWG of test slot is the correct thickness of the sheet.



Although Indian Standard prepared by Bureau of Indian Standards (BIS) formerly ISI (Indian Standard Institute) states that the thickness of sheet and wire should be stated in mm but the practice in industry is still to state the SWG number.

Comments

  1. Thank you for sharing such valuable information and tips. This can give insights and inspirations for us; very helpful and informative! Would love to see more updates from you in the future.

    Elcometer

    ReplyDelete

Post a Comment

Popular posts from this blog

Lathe Operations: Step Turning

Lathe Operations: Plain Turning

What Is Capstan Lathe Machine?