B.D.T PRE-TECHNICAL SKILLS
SETTING-OUT A STRAIGHT WALL
It is the skills and technique required in erecting a straight wall, how to prepare the area, arrangements of tools and materials, and finally setting out the position of the wall.
PREPARING THE AREA FOR SETTING OUT
A piece of land on which a constructional work will be done is known as a site. Preparing a site involves the following:
1. Weeding
2. Burning the weeds.
3. Removing stumps.
4. Removing hills and mounds.
5. Levelling the ground with sand or stones where necessary.
6. Cleaning the ground by picking pieces of unwanted materials.
After going through the above stages then the site is prepared for use.
ARRANGEMENTS OF TOOLS AND MATERIALS
This is also an essential part of the preparation to set-out and build a wall. When the tools and materials are orderly arranged, the following are ensured:
2. It is easy when picking a tool or material.
3. It enhances easy movement while working
The arrangement is as follows:
4. Position the mortar board in the central area of the wall.
5. Allow about 600mm space between the wall and mortar board.
6. Arrange the laying tools on both sides of the board of the board.
7. Pack the blocks or bricks on both sides of the mortar board after the tools.
Setting-out is the process of transferring the measurements and shape of a design from a drawing unto the ground.
DIGGING A TRENCH
-Dig the foundation trench to the required depth and level the bottom. (Pick axe, spade).
-Put pegs in the trench for the required depth of concrete.
FILLING THE TRENCH WITH CONCRETE
1. Measure and mix cement, sand and gravels with water into the ratio 1:3:6.
2. Convey the concrete into the trench to level with the pegs in the trench.
3. Tamp the concrete to consolidate.
LAYING A WALL
After the concrete foundation is dried, the blocks or bricks are bonded to form the wall. The term bonding refers to the arrangements of bricks/blocks in a set order.
Purpose of Building
1. To avoid having continuous joints.
2. To produce a neat and a strong wall.
3. To produce an accurate work.
TYPES OF BONDS
1. Stretcher bond
2. Header bond
3. English bond
4. Flemish bond
TEMPORARILY TERMINATION OF WALLS
There are three methods of terminating a wall temporarily. These are:
1. Racking back
2. Toothing end
3. Block indent
Since not all walls can be completed at a go, the above mentioned methods are used to enable a wall to be continued later.
BDT PRE -TECH
NOTE 2
LAYING TOOLS
The process of raising a wall is termed as laying. Laying involves the use of correct tools and skills. The tools used are known as laying tools.
The following are some laying tools :
TROWEL
It is use for :
-screeding .
-picking and spreading mortar.
-picking and filling gabs with mortar.
plastering.
care and maintenance:
1.wash with water and dry.
2.oil the blade and store in a tool box.
3.never use the trowel for cutting blocks /bricks.
FLOAT
Used to :
1.fill mortar joints together with the trowel.
2.hold mortar when laying blocks and bricks.
care and maintenance:
1.wash and dry after use.
GAUGE ROD.
It is used to check the height of the courses in a wall.
maintenance:
1.wash and dry after use.
2.use it for the appropriate job.
3.it should be kept in a safe place to maintain its accuracy.
STRAIGHT EDGE.
It is used :
1.to set -out the position of a wall.
2.for checking the alignment in wall.
3.together with the spirit level to check the top of a wall.
4.together with the spirit level to plumb a wall.
Maintenance:
1.wash and dry.
2.ensure the edges are not damaged.
SPIRIT LEVEL .
1.it is used for checking vertical straightness -plumbing of wall.
2.checking horizontal straightness -Levelling walls with straight edge.
maintenance:
1.clean after use .
2.handle with care to avoid breaking the glass tube since that would render the tool useless.
MORTAR BOARD.
This is a rectangular wooden board. It is used to store mortar for immediate use.
NOTE 3
SHEET METALWORK
Tools used for soft soldering
The following are the equipment used for soldering :
a) Soldering Bit:This is used to supply the heat to melt the solder and also increases the temperature of the metals being joined.It is made up of the following parts:
-The head which is made of copper.
-The shaft which is made of mild steel.
-The handle which is made of wood.
Copper is used in making the head because it conducts heat quickly to the solder and work being soldered. The handle is made of the wood because it is a bad conductor of heat.
The electrical soldering iron :This soldering iron is used in soldering smaller joints,especially in electrical and electronic appliances. It uses electricity. When connected to electricity, there is an element in it which generates heat to melt the solder.
It is a simple and quick method of soldering.
b) Folding bar:The folding bar is a holding tool. It is made from the cast steel. It is used in folding thin metal sheet at right-angles. The raw hide mallets is used for bending the sheet metal. There are two types of folding bars.
These are the :
-Adjustable type
-Spring type
c) Funnel stake:This is a holding tool. It is made up of a conical head and a stem which is held in the vice.
Uses
It is used for:
*Forming and truing rings
*Forming conical shapes
d) A pair of snips:This is also known as tin-man's snips. This tool is used for cutting thin sheet of metals. Various types are available for cutting different cutting operations.
The two common ones are:
(i)Curved/bent snips-for cutting curved edges.
(ii)Straight snips-for cutting straight edges.
e) Mallet:The tin-man's mallet is used in striking the thin sheet held in a folding bar or on a stake. This is done either to bend or shape the metal sheet.
The mallet consists of:
-Handle:made of wood
-Head:made of raw hide or plastic
The head is made soft so as to avoid damage (dents) the surface of the sheet metal.
