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…

If on-site slump test fails, should engineers allow the contractor to continue the concreting works?

This is a very classical question raised by many graduate engineers. In fact, there are two schools of thought regarding this issue.


The first school of thought is rather straightforward: the contractor fails to comply with contractual requirements and therefore as per G. C. C. Clause 54 (2)(c) the engineer could order suspension of the Works. Under the conditions of G. C. C. Clause 54(2)(a) - (d), the contractor is not entitled to any claims of cost which is the main concern for most engineers. This is the contractual power given to the Engineer in case of any failure in tests required by the contract, even though some engineers argue that slump tests are not as important as other tests like compression test.


The second school of thought is to let the contractor to continue their concreting works and later on request the contractor to prove that the finished works comply with other contractual requirements e.g. compression test. This is based upon the belief that workability is mainly required to achieve design concrete compression strength. In case the compression test also fails, the contractor should demolish and reconstruct the works accordingly. In fact, this is a rather passive way of treating construction works and is not recommended because of the following reasons:


(i) Workability of freshly placed concrete is related not only to strength but also to durability of concrete. Even if the future compression test passes, failing in slump test indicates that it may have adverse impact to durability of completed concrete structures.


(ii) In case the compression test fails, the contractor has to deploy extra time and resources to remove the work and reconstruct them once again and this slows down the progress of works significantly. Hence, in view of such likely probability of occurrence, why shouldn't the Engineer exercise his power to stop the contractor and save these extra time and cost?


㯛瞄؀蠀湉潦›潄畣敭瑮挠湯整瑮氠潯獫氠歩⁥呈䱍倠潲牰敩慴祲਍潎眠牡楮杮⁳牯攠牲牯⁳敷敲映畯摮മഊ䤊普㩯䐠捯浵湥⁴潣瑮湥⁴潬歯⁳楬敫䠠䵔⁌牐灯楲瑥牡൹上慷湲湩獧漠⁲牥潲獲眠牥⁥潦湵⹤਍਍湉潦›潄畣敭瑮挠湯整瑮氠潯獫氠歩⁥呈䱍倠潲牰敩慴祲਍潎眠牡楮杮⁳牯攠牲牯⁳敷敲映畯摮മഊ䤊普㩯䐠捯浵湥⁴潣瑮湥⁴潬歯⁳楬敫䠠䵔⁌牐灯楲瑥牡൹上慷湲湩獧漠⁲牥潲獲眠牥⁥潦湵⹤਍਍湉潦›潄畣敭瑮挠湯整瑮氠潯獫氠歩⁥呈䱍倠潲牰敩慴祲਍潎眠牡楮杮⁳牯攠牲牯⁳敷敲映畯摮മഊ䤊普㩯䐠捯浵湥⁴潣瑮湥⁴潬歯⁳楬敫䠠䵔⁌牐灯楲瑥牡൹上慷湲湩獧漠⁲牥潲獲眠牥⁥潦湵⹤਍਍湉潦›潄畣敭瑮挠湯整瑮氠潯獫氠歩⁥呈䱍倠潲牰敩慴祲਍潎眠牡楮杮⁳牯攠牲牯⁳敷敲映畯摮മഊ䤊普㩯䐠捯浵湥⁴潣瑮湥⁴潬歯⁳楬敫䠠䵔⁌牐灯楲瑥牡൹上慷湲湩獧漠⁲牥潲獲眠牥⁥潦湵⹤਍਍湉潦›潄畣敭瑮挠湯整瑮氠潯獫氠歩⁥呈䱍倠潲牰敩慴祲਍潎眠牡楮杮⁳牯攠牲牯⁳敷敲映畯摮മഊ

Comments

Popular posts from this blog

Lathe Operations: Step Turning

Lathe Operations: Plain Turning

What Is Capstan Lathe Machine?