JSS 3 SECOND TERM BASIC TECH WEEK 4
Topic: PRINCIPLES OF MEASUREMENT AND MEASURING
Design in Metalwork
The projects in metalwork involve construction and application of shaped figures on thin gauges of sheet metal. Attempt is made here to give guideline to enable each student to produce a useful item. The main basic operations in metalwork (i.e. cutting and filling) are put into consideration, and all the acknowledged gained in geometrical construction is the basis of metal works, students are expected to produce the try-square, using necessary hand tools. The various items are expected to be made of thin gauged metal folded to shapes, students are exposed to more useful items which are aimed at giving full confidence in practical work which gives us the average sizes of different furniture items as a guide for both woodwork and metalwork projects.
Step 1: Draw a circle large enough for a centre table (e.g. 1 metre).
Step 2: Divide the circle into three equal parts
Step 3: Find the centre of each radius.
Step 4: With these centres and radius AO, draw areas to form semi-circles which will represent a large end of each stool.
Step 5: Round up the edges at the main circle.
Step 6: Ensure that the height of the leg is 350mm.
Tools
Cutting Tools
In sheet metalwork, we use a tool that does the work of scissors. It is called tin snipes.
Types of Tin Snips
It is important to use the correct tool and the correct method of cutting to ensure that maximum efficiency is achieved. As mentioned earlier, tin snips and shears are the commonest tools used in cutting sheet metal. The following types of tin snips are used for various types of job.
i. Straight Snips: This types is used for straight cuts and for trimming surplus metals. It is also used for cutting out joint allowance at fold lines.
Straight snips
ii. Bent Snips: As the name suggests, this type of snips is bent. It is used for cutting circular shapes and internal curves.
iii. Universal Snips: This type is a combination of the straight and curved snips. The handles are offset, thereby allowing cuts to be made in any direction with a minimum effort. The universal snips are used to cut sheet metals into various shapes.
Other Tools Used in Sheet Metalwork
Other tools used in sheet metalwork are the marking out and measuring tools such as scriber, try-square, steel rule, dividers, outside calipers, inside calipers, odd-leg calipers.
Bending Sheet Metals
Bending and folding are very necessary process in sheet metalwork. Before we discuss the tools used for these processes, let us first all know what they means. Bending in sheet metalwork means causing the flat material