Lesson Notes By Weeks and Term - Junior Secondary School 1

SUBJECT:  BASIC TECHNOLOGY           

CLASS:  JSS1

DATE:

TERM: 3RD TERM

REFERENCE MATERIALS 

• MELROSE, Basic Science and Technology Book 1
• NERDC, Basic Technology for JSS, Book 1

WEEK FOUR

TOPIC: METAL WORK- HAND TOOL-Marking out and measuring tools

Metal is one of the materials used in technology for construction and fabrication of devices. Metal as a material can be fabricated into various shapes and products. However, to be able to do that, you need appropriate tools.  These tools are either hand tools or machine tools.

MARKING OUT TOOLS:

Marking out tools are hand tools used for making lines on metal surfaces, checking alignment, and indicating points or positions on a work piece.

Tools for making out in the workshop include: 

1. Surface plate 
2. Surface table
3. Scriber
4. Odd-leg caliper 
5. Divider 
6. Punches
7. Try square
8. Box Square 

Surface plate 

The surface plate is a precision piece of equipment with a flat surface of high-grade finish, on which work piece are placed for marking out. It is also used for testing the flatness of surfaces.

Care of surface

1. Cover the surface after use to keep it free from dirt
2. Do not hammer it.
3. Do not scratch or deform the surface

Surface table

The surface or marking out table is larger than the surface plate. It is used for supporting bigger work piece, so that marking out can be carried out with ease and accuracy. It is made up of cats iron and has  a high grade surface.

Scriber

The scriber is the metal worker’s pencil. It is used for marking out lines by hand and together with straight edges like steel rules, try squares or box rules. It is made from high carbon steel or stainless steel, hardened and tempered. They are of various sizes.

Divider 

Dividers are two-legged steel instrument used for scribing arcs, curves and for setting off distances. Dividers are available in various sizes, and may be available in various sizes, and maybe spring-loaded with a fine adjusting screw or may be firmly joined at the head.   

Punches

This is either a medium or high carbon steel material. We have dot punch and the centre punch.

Dot Punch: This is used for denting scribed lines. This is done some space apart; to make the lines indelible while one is working. It is 600 at its conical end.

Centre Punch: It is used for providing a heavy conical dent at the end point where a hole will be drilled in a work piece. This prevents the drill from deviating from the current location of the hole. It is 900 at its conical end.

Try square:  The try square is used for testing the squareness of surface, and marking out lines at right angles to given edges. It is a high precision tool that should be handled with care. The stock and the blade, which are the main parts, make 900 with each other

Box Square:  The box square is used for the making parallel lines on a round bar, It is made from medium carbon steel (hardened and tempered) and has graduations on its body to facilitate marking off dimensions, while marking out 

Evaluation 

1. Define marking out tools 
2. State 8 marking out tools and their uses.

MEASURING TOOLS

Measuring tools are tools of measuring lengths, widths, thicknesses, or sizes of metals. Measuring is usually done during marking out.

Common measuring tools include the following:

1. Steel rule 
2. Caliper   
3. Combinations sets
4. Micrometer
5. Vernier Caliper 
6. Depth gauge 
7. Height gauge 

Steel rule 

The steel rule is made of carbon steel or stainless steel. It is graduated in millimeters and centimeters. To take a measurement with it, the steel rule should be placed on its edge to touch the work, so that an accurate reading can be taken from the centre of the division lines.

Caliper   

Calipers are used for measuring diameters, width, and thickness of objects.

We have:

1. External Caliper: It is used for measuring diameters, width, and thickness from the outside of the objects.
2. Internal Caliper: It is used for measuring diameters, width, and thickness from the inside of the objects.
3. Odd-leg Caliper: It is used for measuring diameters, width, and thickness from the middle of the objects to the outside.

Combinations sets

The combination set, as the name implies, is a measuring instrument, which consists of three heads: 

1. The centre square: It is used to determine the centre of round shafts or holes
2. The square head: It is used for measuring and setting out 900 and 450 angular surfaces. It is a standard tool, which require no setting.
3. The protractor head: It performs dual functions as (i) marking out tool and (ii) measuring tool. It is a semicircular precision tool for measuring angular surfaces. It is graduated between 00 and 1800.

Micrometer

It is used for taking precision measurements. We have both internal and external micrometer, which are used for measuring diameter of small objects in millimeter.

Vernier Caliper 

It is used for both external and internal precision (accurate) measurements of objects in centimeter.

Depth gauge 

It is used for measuring the depth of holes similar to that of an outside micrometer.

Height gauge

It is used to perform two functions namely:

1. To determine the height of components.
2. To mark out dimensions.

GENERAL EVALUATION

1. Define measuring tools 
2. State 5 measuring tools and their uses.
3. Define marking out tools 
4. State 8 marking out tools and their uses.

READING ASSIGNMENT

Read about MORE ON HAND TOOLS.

REFERENCE MATERIALS 

NERDC- BASIC TECHNOLOGY BOOK 1, page 

WEEKEND ASSIGNMENT 

1. Which of the following is not a material used in technology? (a) Metal and Wood (b) Plastic and Rubber (c) Ceramic (d) Internet
2. The following are marking out tools except ___(a) surface plate (b) scriber (c) hammer (d) try square 
3. The following are measuring tools except ___(a) steel rule (b) scriber (c) caliper (d) micrometer
4. Which of the following is the metal worker’s pencil (a) surface plate (b) scriber (c) hammer (d) try square
5. Which of the following is used to determine the centre of round shafts and holes (a) try square  (b) centre square (c) set square (d) diameter square

THEORY 

1. Define the following hand tools (i) marking out tools (ii) measuring tools
2. State (i) 8 marking out tools (ii) 5 measuring tools