Operating small power tools
Portable power tools 2
Safety instructions 2
Portable electric generators 4
Electric drills 4
Circular saws 7
Jig saws 8
Routers 8
Angle grinders 9
Explosive-powered fastening tools 11
Direct-acting tools 11
Indirect-acting tools 11
Safety 12
Pop (R) Riveting 13
Hand compression tools 15
Summary 18
Answers to Student exercises 21
Portable power tools
Portable power tools are commonly used in electrical work. Manufacturers’ instructions must be referred to for step-by-step instructions. Care and maintenance should be observed.
Safety instructions
Safety First - Read the manual carefully and learn the applications, operating limitations and potential hazards of the tool before attempting to operate it.
NOTE: When servicing - use only identical replacement parts.
Pay particular attention to the following important points.
· Keep work area clean. Cluttered areas and benches invite accidents.
· Avoid dangerous environment. Do not expose tools to rain. Do not use power tools in damp or wet locations and keep work area well lit.
· Keep children away. All visitors should be kept at a safe distance from work areas.
· Store idle tools. When not in use, tools should be stored in dry, high or locked-up places, out of reach of children.
· Do not force a tool. It will do the job better and more safely at the rate for which it was designed.
· Use the right tool. Do not force a small tool or an attachment to do the job of a heavy duty tool.
· Wear proper apparel. Loose clothing or jewellery will get caught in moving parts. Rubber gloves and footwear are recommended when working outdoors.
· Use safety glasses with most tools, also a face or dust mask if the cutting operation is dusty.
· Do not abuse cord. Never carry a tool by the cord or yank it to disconnect it from a receptacle. Protect the cord from heat, oil and sharp edges.
· Secure work. Use clamps or a voice to hold work. It is safer than using your hand and it frees both hands to operate the tool.
· Do not over-reach. Keep proper footing and balance at all times.
· Maintain tools with care. Keep tools sharp and clean at all times for best and safest performance. Follow instructions for lubricating and changing accessories.
· Disconnect tools when not in use, before servicing, or when changing accessories such as blades.
· Remove adjusting keys and wrenches. Form the habit of checking to see the keys and adjusting wrenches are removed from the tool before turning it on.
· Avoid accidental starting. Do not carry a plugged-in tool with a finger on the switch. Be sure the switch is off when plugging in.
· Outdoor use of extension cords. When a tool is used outdoors, use only extension cords suitable for use outdoors.
· Do not operate portable electric tools in gaseous or explosive atmosphere. Motors in these tools normally spark and sparks may ignite fumes.
Extension leads
· When using a tool at a considerable distance from the power source, an extension cord of adequate size must be used for safety and to prevent loss of power and overheating.
· Before using cords, inspect them for loose or exposed wires and damaged insulation. Make any needed repairs or replacement before using your power tool.
· When extension cords or power tools are being used in open or damp situations, the chance of damage or current leakage to the frame of the tool or the material being machined is very high and could result in severe electric shock.
· To prevent any harm coming to the operator or his workmates in this situation, the use of a ‘core balance earth leakage protection system’ is strongly recommended. These are readily available already incorporated into a plastic container with a lead and plug on one end and a double outlet on the side of the box.
Portable electric generators
Electricity generators are often used in remote locations. The generator is mounted onto a frame and is ideal for lifting into location, see Figure 11.
The starting operation is similar to a lawn mower in that it has a cord start, petrol mix and a throttle to control speed.
The speed of the motor is automatically increased as more electrical power is required, this is achieved by means of a ‘governor’.
WARNING: An electric shock from a portable generator may be fatal.
Figure 1: A portable generator
Electric drills
Figures 12, 13, 14 and 15 show different types of drills.
Electric drill features
· speed variation (mechanical or electronic)
· different capacity chucks (6 mm to 12 mm)
· may be of the Hammer type (suitable for drilling masonry)
· may be used as a powered screwdriver
Care of electric drills
Any motor driven device may easily be damaged by stalling. Stalling causes the motor to draw 4-6 times the normal maximum current, and since the heat produced is proportional to the square of the current, overheating and burnout occurs rapidly.
Stalling may be minimised by using the correct bit or drill for each job and by keeping it sharp.
WARNING: When working near live conductors and using an electrical tool, drill etc, be careful when using ‘earthed’ appliances as contact with both conductor and appliance case may be fatal!
Figure 2: Example of a portable electric drill
Drills most commonly range in 6, 10 and 13 mm sizes for both general and ‘in use’ applications. The size designation of the drill (6, 10 or 13 mm) refers to the maximum diameter drill bit or accessory attachment shank that will be accepted by the chuck of the drill. Generally, as the chuck size increases, so does the work capacity of the drill. 10 mm drills are geared to deliver slower speeds and more torque, or twisting power, than 6 mm drills, while 13 mm drills offer still slower speeds and more torque than 10 mm models.
A 6 mm drill is a good choice for the home handyman requiring high speed drilling capacity in most woods and composition and adequate power for intermittent light duty drilling in masonry and metals.
Figure 3: A light-duty portable drill
A 13 mm drill is the most appropriate for bigger projects and more frequent use in concrete, or with large hole saws. A 13mm drill is also the best choice for the tradesman or for continuous heavy duty use.
Figure 4: A heavy drill
Used where large-scale masonry drilling is to be carried out. This drill also provides an ‘impact’ action that actually ‘hammers’ the drill bit into the masonry.
Figure 5: A hammer drill
Cordless drills
These drills are a rechargeable battery as their power source. They are capable of performing as well as any of the 10 mm drills with the added advantage that they can be used where no electrical power is available.
Circular saws
A wide range of portable circular saws is available today for both home and constructional use (See Figure 16.) Their cutting power and speed make them useful in many situations. On-the-job portability is another advantage that eliminates the need to manhandle large, heavy or awkward pieces of timber.
Generally, the motors are rated from 1 kW to 2 kW. Where the saw is to be used for heavier work, or consistently for extended periods of time, a heavy duty machine with a larger motor should be used to prevent overheating.
Figure 6: A circular saw
Jig saws
A jig saw (Figure 17) consists of a small blade attached to the tool by means of a mechanical linkage that moves the blade up and down at approximately 2500 strokes per minute. Because the blade is so narrow, it can be used to cut curved lines. The jig saw can also be used for cutting out shapes within a board; in this case a starting hole must first be drilled. Different blades which will allow it to cut almost any material can be obtained for this tool.
Figure 7: A jig saw
Routers
The router has a cutting tool similar to that of a milling machine, but is generally smaller. The router can be used for cutting grooves, trimming laminates, cutting decorative edgings and a wide variety of joinery work, in addition to electrical applications.
Figure 8: A router
Angle grinders
Angle grinders are used for cutting off metal strips, tubing, angle iron, tiles and masonry. Can also be used for the sanding flat of welded joints and masonry. (See Figure 19.)
This tool basically uses two types of cutting disc and various sanding discs, depending on the work material.
Figure 9: An angle grinder
Student exercise 11 When using portable power tools you should
(a) keep safety guards in .
(b) keep away from cutting area.
(c) keep work area .
(d) avoid environments.
(e) keep away.
(f) idle tools.
(g) do not tool.
(h) use tool.
(i) wear clothing.
(j) use glasses.
(k) do not cord.
(l) secure .
(m) oversearch.
(n) care and tool.
(o) unused tools.
2 How may stalling of a power drill be minimised?
3 The better power drill to use when working near live conductors is
4 What sort of power drill would you find more efficient drilling through masonry?
5 What types of discs can you use on angle grinders?
Check your answers with those given at the end of this topic.
Explosive-powered fastening tools
Powder-actuated fastening tools are commonly referred to in the trade as ‘Ramset guns’. This is incorrect; they are not guns but fastening tools. They cannot be used as guns because of certain built-in safety features.
As many different brands of powder-actuated fastening tools are available, it is incorrect to generalise and call them all ‘Ramset tools’; ‘Ramset’ is only one of those available.
The powder-actuated or explosive-powered fastening system provides a quick, efficient means of securing equipment, brackets, clips and other components to concrete, steel or brick.
Direct-acting tools
These tools apply the driving force of the explosive charge directly to the fastener which then travels down the barrel and is forced into the work surface.
The fastener is loaded into the breech of the tool and the correct strength power load is placed immediately behind the fastener. When the tool is closed, pressed against the work surface and fired, the fastener travels down the barrel at high speed and enters the work surface.
Indirect-acting tools
These tools apply the force of the explosive charge to act on a piston which in turn hammers the fastener into the work surface. These tools are loaded differently to direct-acting tools in that the fastener is loaded into the muzzle of the tool and is therefore resting against or near the work surface at the time of firing. This reduces the velocity of the fastener and the likelihood of the fastener going into free flight, whether through ricochet from or perforation of the work surface.
No powder burning of the work surface occurs when using indirect-acting tools because the spent gases are vented from the tool behind the piston.
Safety
Because these tools use an explosive charge to drive the fastener into the work surface (and in the case of the direct-acting tool, the fastener travels at a high speed), extreme safety precautions must be taken and care exercised in their operation.
Operators intending to use powder-actuated tools should be adequately trained in every aspect of their use.
Most manufacturers of these tools run approved operators’ training courses, leading to an Operator’s Licence for those who successfully finish the course and pass the licensing authorities’ test and requirements.
Powder-actuated tools have built-in safety devices that automatically operate every time the tool is loaded and fired.
Direct-acting tools have the following safety features:
· The tool cannot be accidentally fired if it is dropped on a solid surface.
· The tool cannot fire if it is tilted at an angle in excess of 7° from the work surface.
· The tool cannot be cocked if it is pressed against an uneven surface.
· The tool must be pressed against a solid and reasonably level surface with a pressure that will overcome the spring-loaded tip before it is fully cocked.
· The tool will not accidentally open when it is cocked prior to firing.
· This is termed ‘interlocking’.
· All direct-acting tools are fitted with an approved safety shield, giving 50 mm of cover all around the barrel. The shield is capable of preventing the escape of a fastener should it be deflected while entering the work surface.
· The tool cannot be air-fired by merely loading the tool and pulling back on the safety shield.
· The tool will not cock or fire if the safety shield has been removed.
Indirect-acting tools contain all the built-in safety features of the direct-acting tools, with the exception of the safety shield.
Handling of a tool
A tool should be transported in a case especially designed for it. Take care when removing or carrying the tool. Do not drop it or experiment with it.
Explosive charges
The explosive charges provide the driving force for the fastener to penetrate into the work surface.
Because the fastener requires different forces to penetrate concrete, steel or brick and also because the required depth of penetration varies, explosive charges of different power ratings are made. These explosive charges are very similar in appearance to a blank cartridge for a rifle.