Lathe Operations: Facing

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…

Requirement, Service and Maintenance of Oxygen System

Requirements of Typical Oxygen Installation. The requirement which to be have satisfied to unable an oxygen installation to function efficiently is as follows:

 (a) A means of storing oxygen in the aircraft.

 (b) A means regulating the flow to the crew member only as he breathes in and an indication that oxygen is flowing to his position.

 (c) A means of regulating the oxygen to the user remembering that the higher it files, the more oxygen, he will require.

 (d) The means of coupling various components together and switching them on and off as required.

Component which meet requirements are the aircraft cylinders, regulators flow indicators ,economizers, masks charging and line valves, high medium and low pressure pipe lines, filters, non returns valves connecting pieces, transport cylinders, charging pipe lines and charging regulators.

Service and Maintenance of Oxygen System. The service and maintenance of oxygen systems should be performed only by technicians who are qualified through training and experience. Oxygen is not an explosive and is not flammable in its pure state, but it supports combustion. Sometimes violently, when it contact or mixed with other materials. It is, therefore, important that certain precautions be exercised when working with oxygen system. The following are essential:

 (a) Smoking, open flames, or items that may cause spark, must not be permitted near aircraft when maintenance is being performed on the oxygen system.

 (b) All electrical power must be performed on the oxygen system must be grounded.

 (c) Oxygen must not be permitted to come in contact with oils, greases, or solvents. Such contacts can cause spontaneous explosions.

Oxygen cylinders are inspected for damage such as nicks, dents, corroded fittings, hydrostatic test date, DOT designation and leakage.  Cylinders that do not meet requirements must be completely disassembled and inspected in an approved facility.  DOT numbers, serial numbers, and dates of hydrostatic testing are stamped on the shoulder or neck of each cylinder.

Whenever a component of a high pressure oxygen system has been removed and replaced or whenever the system has been disassembled in any way, the system must be tested for leaks and purged.  The leak detector solution (soapy water) is completely removed after each test and wherever leaks are found, fitting must be repaired or replaced.

Purging the Oxygen system involves fully charging the system in accordance with service instructions and then releasing oxygen from the system. The airplane should be out door if possible; otherwise it should be isolated in a well ventilated building with no smoking or open flame permitted in the area. No grease or other lubricants should be near enough to come in contact with the Oxygen. The doors and windows of the airplane must be open.

After the system is fully charged with oxygen, all oxygen marks are plugged into their outlets and the oxygen is allowed to flow for about 10 minutes. When the Oxygen is flowing from the masks in odorless, the purging is complete and the oxygen is shut off. The masks are removed from their outlets and the system is recharged. Recharging is usually accomplished through a filling value and fitting mounted conveniently on the lower part of the airplane or accessible through the baggage area. The cap is removed from the fitting and the refill hose is connected oxygen is allowed to flow into the system until it is automatically or manually shut off when the required pressure is registered on the high pressure oxygen gauge. Do not assume that because a cylinder is colored green, it contains breathing oxygen. Cylinders containing other gases are sometimes colored green.


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