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…

Electrical Components Used in Aircraft

Starter Generator. It is a DC machine with compound excitation used in aircraft.  It is designed for starting the engine and then to serve as a DC supply source to the aircraft and charge the storage battery. The main aircraft engine drives the starter generator.



Ampere Hour Meter. An integrated ampere-hour meter serves to indicate the capacity of the storage batteries. In AH



Over Voltage Protection Unit. This unit is intended to protect the generator from overloading due to increased voltage in case of regulator failure. When the voltage increases beyond a safe value this unit cuts off the supply of differential relay and thereby disconnecting the generator from the mains.



Centralized Warning Panels. The centralized warning system provides the pilot with immediate indication on failures or emergency conditions in certain system of aircraft, which could be hazardous to pilot and aircraft.  It incorporates two types of warning, designated as primary and secondary:-



 (a) Primary Warnings. These are dangerous warning as main hydraulic pressure failure, fire in engine compartment, DC generator failure and fuel reminder etc. Primary warning lights the red warning lamps on the instrument panel and red caption on the centralized warning panel, to identify the particular warning source.



 (b) Secondary Warnings. It lights up the amber captions on the centralized warning panel to identify the particular warning source and initiate flashing of the attention lamp. These warnings do not produce an alarm as RT failure, undercarriage warning.



Invertors. It is a device which converts 28V DC into 115V, 400 Hz, 1f / 3f AC.  These are divided into two types as:-



 (a) Rotary Invertors. It is a combination of DC motor and AC Generator having separate armature and rotor winding, both sharing a common field.  It is also called mechanically operated invertors, i.e., dc motor driving an ac generator.  These are available in Single phase or three phase type.  These are being used in old version aircrafts.



 (b) Static Invertors. The purposes of static invertors are same as rotary invertors i.e., to convert dc supply into ac supply.  It is also called electronic invertors because its principle is based on Silicon Control Rectifier (SCR). These are used in modern aircraft, due to quicker in response, no radio interference, power consumption is less, and compact in size, weight is less.  It provides supply to various aircraft loads as Radio, Radar, Autopilot instrument etc. It is also used as standby source in case of aircraft supply failure.



Carbon Pile Voltage Regulator. This unit maintains the generator voltage constant at prescribed value, when load or speed of generator is changed.



Methods of Voltage Regulation. There are following methods used for voltage regulation:



(a) Two Coils Method.



 (b) Negative feedback method.



 (c) De-compounding method.



 (d) Equivalised voltage control method (EVC).

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