SECOND TERM LESSON NOTE FOR WEEK
CLASS : JSS 3
SUBJECT : BASIC TECHNOLOGY
TOPIC : SIMPLE METAL WORK PROJECTS
SHEET METAL WORK
The sheet metal work is the process of making articles with the tin plate whose diameter (thickness) is below 5mm. This method is called Metal Fabrication. The forms of metal usually used for sheet metals work is the Tin plate which is made from mild steel with low carbon content. The following processes are the steps used to carry out sheet metal work project. They are:
1) Measuring
2) Marking out
3)Cutting
4) Assemble.
TOOLS USED FOR CUTTING SHEET METAL
The tools for cutting sheet metals include:
a. A pair of tin snips
b. Bench shear
c. Hack saws
d. Jeweler’s saw
e. Chisels
f. Scriber.
SCREW THREAD FORMING:
The screw thread forming is the process of winding groove round a metal bar. The screw thread forming provides a temporary fastening devices and it transmits motion.
There are two types of screw thread forming:
1) The internal screw thread forming: is the formation of screw thread using tap cut. A tap wrench is a tool used to hold tap when cutting internal thread by using hand method.
2) The external screw thread forming: is the formation of screw thread using die and stock to cut. A die is a hand tool normally fitted to the stock when cutting external thread on the outside of the round metal bar. Examples of thread are:
I) Vee Thread: This is generally used in engineering work. It is cheap, strong and easy to cut by hand.
II) Acme Thread: this is used for the transmission of power in motion.
III) Buttress Thread: This is used when screw has to resist force in the same direction as in vice. It is used for quick release of mechanism.
IV) Square Thread: This is used mainly to transmit rotary motion into the linear motion as in a machine. It is used for screw jack.
The screw threads have three applications, which are:
a. To fasten parts together.
b. To read just the position of parts.
c. To transmit power in motion.
METAL FINISHING.
Generally, metal finishing is the process of applying protective and decorative materials to the surface of the metal. For instance, by spraying a car. Other process of metal finishing includes;
A) Buffing: This is the process of polishing the surface of metal on buffing machine.
B) Scratching: This is process of cleaning the surface of the metal and covering it with melted wax or asphalt and allowing it to dry.
C) Spot finishing: this is an ornamental finish on the surface of a metal in order to give the metal a good surface look.
D) Lacquering: this is the process of spraying lacquer gun to prevent rusting.
E) Electroplating.
F) Enamelling
G) Galvanizing.
REASONS FOR METAL FINISHING.
The reasons for applying finishes into the surface of metal include:
a. To protect the metal surface against rusting.
b. To give the metal a good decorative coating.
c. To give the metal a good protective coating.
d. To reduce the rate of wear of the material.
c. To give the metal an attractive appearance.
METALWORK JOINING.
Metal joining can be defined as making two metal surfaces to be joined together. There are two types of joining metal, which are:
1) Permanent Joining: this is process of joining metal together in order to make it fastened together permanently in which it cannot be dismantled again unless the work is damage.
2) Temporary Joining: this is process of joining metal together in order to make it fastened together temporarily in which it can be dismantled again without any damage to the work.
METHODS OF JOINING METAL SURFACES.
There are five (5) methods joining metal surface together, which are:
1) Soldering method (Permanent): this is a permanent method of joining metal surfaces together by means of an alloy called solder, which has lower melting point than the other metals being joined by the application of heat energy. There are two types of soldering, which are;
i) soft soldering and
ii) hard soldering.
2) Brazing method (Permanent): this is a modified form of soldering process using alloy of copper 65% and zinc 35% which has melting point. When the filler rod is used in joining of metals, the process is called brazing. There are three commonly types of brazing, which are copper brazing, silver brazing and aluminium brazing.
3) Welding method (Permanent): this is a fabricated method of joining metal surface together permanently by heating them until they melt and get attached to each other by a process called fusion of metal. This flame known as oxy-acetylene flame. A person who welds is a Welder. Welding can be grouped into two methods, which are:
4) The electric arc welding method: it involves the use of heat from electricity or generator as a source of heat to melt electrodes on the metal (work piece).
5) The Gas welding method (oxy-acetylene): it involves the use of oxygen gas and acetylene gas which are stored in gas cylinder.
6) Riveting method (Permanent): this is a method of joining metal pieces together permanently by inserting a metal rod called rivets into the holes drilled through the metal pieces.
7) Mechanical Fastening method (Temporary): this is a temporary method of joining metal surfaces together by the uses of Bolt and Nut; screws with nut; stud with nut. This method makes it possible to dismantle and assemble parts together by the use of spanners or screw drivers.
These are various kind of metal work projects that can be done practically, they include;
a. Key-holder: This is a device used for holding keys of lock so as to make them easier to handle.
b. Scraper: This is a device used for scraping away materials from the wooden surface and to make it smoother and neater.
c. Bottle opener: This is a device used for opening caps of bottled drinks.
d. Pen Knife: This is a device used for cutting any stuck items whenever necessary.
e. Spanner: This is a device used to loosen and tightened a bolt and nut.