Marking Out and Measuring Tools: Metal Work Hand Tools – JSS1 Basic Technology Lesson Note (Third Term)

Marking-out and measuring tools are metalwork hand tools used to draw lines, mark positions and take sizes on a metal workpiece before cutting or drilling.

Behavioural objectives

1. Define marking-out tools and measuring tools.
2. List the common marking-out tools and state the use of each.
3. List the common measuring tools and state the use of each.
4. State how to take care of a surface plate.
5. Distinguish between a dot punch and a centre punch.

What are metalwork hand tools?

Metalwork hand tools are tools worked by hand and used to shape, mark, measure and join metal.

• Use of metal: metal is fabricated into many shapes and products, such as gates, window frames and machine parts.
• Hand tools: tools worked by the power of the hand, such as a scriber, a steel rule and a try square.
• Machine tools: tools worked by a machine, for example a lathe or a drilling machine.
• Need for the right tool: good work depends on choosing the correct tool for each job.

What is the difference between marking-out tools and measuring tools?

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

Measuring tools are tools used to measure the lengths, widths, thicknesses or sizes of metals, usually during marking out.

What are the marking-out tools?

There are eight common marking-out tools: surface plate, surface table, scriber, odd-leg caliper, divider, punches, try square and box square.

Surface plate

The surface plate is a precision piece of equipment with a flat, high-grade surface on which workpieces are placed for marking out.

• Use 1: holds the workpiece while it is marked out.
• Use 2: tests the flatness of surfaces.

How do you take care of a surface plate?

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 table, also called the marking-out table, is a larger table that supports big workpieces during marking out.

• Size: larger than the surface plate.
• Material: cast iron, with a high-grade surface.
• Purpose: lets marking out be done with ease and accuracy.

Scriber

The scriber is the metal worker’s pencil, used to scratch lines on metal.

• Use: marks lines by hand, together with a straight edge such as a steel rule or try square.
• Material: high carbon steel or stainless steel, hardened and tempered.
• Sizes: made in various sizes.

Odd-leg caliper

The odd-leg caliper is a marking-out tool with one bent leg and one straight leg.

• Use 1: scribes lines parallel to an edge of the workpiece.
• Use 2: helps to find the centre of a round bar.

Divider

The divider is a two-legged steel instrument used for scribing arcs and curves and for setting off distances.

• Sizes: available in various sizes.
• Spring-loaded type: has a fine adjusting screw.
• Firm-joint type: the legs are firmly joined at the head.

Punches

There are two types of punch: the dot punch and the centre punch, both made of medium or high carbon steel.

• Dot punch: dents scribed lines at intervals so the lines stay visible while one works.
• Centre punch: makes a heavy conical dent where a hole will be drilled.

Try square

The try square is a tool for testing the squareness of a surface and for marking lines at right angles to an edge.

• Main parts: the stock and the blade.
• Angle: the stock and the blade make 90° with each other.
• Handling: it is a high-precision tool and must be handled with care.

Box square

The box square is a tool for making parallel lines on a round bar.

• Material: medium carbon steel, hardened and tempered.
• Graduations: marks on its body help with marking off dimensions.

What are the measuring tools?

There are seven common measuring tools: steel rule, caliper, combination set, micrometer, vernier caliper, depth gauge and height gauge.

Steel rule

The steel rule is a straight strip of steel marked in millimetres and centimetres.

• Material: carbon steel or stainless steel.
• Use: measures lengths and widths, and guides the scriber when drawing lines.

How do you measure with a steel rule?

1. Place the steel rule on its edge so that it touches the work.
2. Read the measurement from the centre of the division lines.
3. Look straight down at the marks to read accurately.

Caliper

There are three types of caliper: external, internal and odd-leg. Calipers are used for measuring the diameter, width and thickness of objects.

• External caliper: measures diameter, width and thickness from the outside of the object.
• Internal caliper: measures diameter, width and thickness from the inside of the object.
• Odd-leg caliper: sets a fixed distance from an edge, and is used from the middle of the object to the outside.

Combination set

The combination set is a measuring instrument with three heads, as its name implies.

• Centre square: finds the centre of round shafts or holes.
• Square head: measures and sets out 90° and 45° angular surfaces. It is a standard tool and needs no setting.
• Protractor head: serves as both a marking-out tool and a measuring tool. It is a semicircular precision tool for measuring angles, graduated from 0° to 180°.

Micrometer

The micrometer is a precision tool for measuring the diameter of small objects in millimetres.

• Types: internal and external micrometers.
• Use: taking precision measurements.

Vernier caliper

The vernier caliper is a precision tool for taking accurate measurements of objects.

• External measurement: measures the outside size of an object.
• Internal measurement: measures the inside size of an object.

Depth gauge

The depth gauge is a tool for measuring the depth of holes.

Height gauge

The height gauge is a tool with two functions.

• Function 1: determines the height of components.
• Function 2: marks out dimensions.

Evaluation

1. Define marking-out tools.
2. State 8 marking-out tools and their uses.
3. Define measuring tools.
4. State 5 measuring tools and their uses.
5. State the angle at the conical end of a dot punch and of a centre punch.

Assignment

Answer all parts of this task.

1. State two ways of taking care of a surface plate.
2. Write two differences between a dot punch and a centre punch.
3. Name the three types of caliper and state what each one measures.