Main Types Of Power Tools

Variable-speed drills

One of the most significant developments in DIY power tools has been the introduction of the electronically controlled variable-speed drill. This is the most suitable model for the home handyman because it can drill holes at the ideal speeds required for different materials.

Developments in micro-electronic technology have made possible variable-speed drills where the speed is automatically maintained regardless of the resistance encountered in a particular material.

Two-speed drills

You should not be misled into thinking that a single-speed drill with a high speed rating will effectively cover all drilling requirements. Considering the variety of jobs you may undertake the single-speed drill is positively unsuitable and should not be seriously considered.

Every material has its own ideal drilling speed. Also the size of the hole to be drilled is important. As a general rule the larger the hole the slower the speed that is required.

A two-speed drill is normally adequate for most drilling jobs around the home. The slower speed is used for drilling masonry and larger size holes in most materials, and the higher speed is used to drill most small holes and to drive attachments.

Hammer drills

Percussion or hammer drills make easy work of drilling in masonry and concrete. They form an increasing proportion of the DIY drills sold.

Rotary drills can be used to drill masonry and ordinary house brick but regardless of how powerful they are this tends to be extremely hard work and causes excessive wear on the drill bits.

The percussion device delivers rapid blows to the drill bit at a rate of up to 35,000 blows per minute. This hammering, combined with the normal rotary action, breaks up any small stones or flint at the drill point and considerably speeds up the drilling of holes in masonry.

The final choice

When you have seen the range of power drills available, consider carefully before making a final choice. Prices can vary enormously between different makes and types, but do not attach too much importance to price. There is no point in buying a drill because it is cheap only to discover later that its use is too limited.

It is important that you buy a drill which will cope adequately with the envisaged workload. However, it is likely that you will soon discover how the electric drill can open up new horizons, making possible many previously impossible jobs.

Circular saws

The circular saw has one basic function, to cut fast and accurately in a straight line. Circular saws are classified in size by the blade diameter. They can be divided into three, general types. The smaller 150mm (6in) has a maximum depth of cut of around 36mm (11/2in). This is reduced to 18mm (3/4in) when a bevel cut of around 45° is made. This type is sufficient for most light cutting work.

However, if rebuilding or renovation work is being done it will involve for example cutting planks of 4X2in timber. For this type of work a larger saw around 190mm (71/4in) is necessary. This type has a depth of cut of just over 60mm (27/thin) and should cope adequately with most jobs around the home. The larger 225mm (9in) industrial circular saw should be considered for heavy work.

Using the correct blade the circular saw can cut a wide variety of materials. Consult the manufacturer’s specification for recommended types of blade.

Blade types

For general purpose fast cutting in timber use a crosscut blade. For a fine finish in timber use a flooring blade. This is designed specially for cutting old floors and suchlike where nails may be encountered. Note that only the specially hardened flooring blade is recommended for sawing where there may be nails. Nails will destroy the teeth of other blades. Aluminium oxide abrasive discs are used for iron and steel. Silicone carbide abrasive discs are used for stone, brick, slate and marble. The tungsten carbide tipped blade is one of the hardest known materials and one of these blades will keep a sharp cutting edge up to 40 times longer than a normal blade. While costing between two and five times as much they represent excellent value for money, saving the resharpening and replacement costs of a normal blade.

Check the set of the teeth frequently to keep drag to a minimum.

Be very careful when using a circular saw. The blades are sharp and travel very quickly. It is essential that both upper and lower blade guards are fitted.

Jig saws

The jig saw is more versatile than the circular saw. It can be used for intricate, curved work as well as straight cutting. The compact design of the jig saw means it is also more suited to cutting in places where space is limited.

The selection of blades available for the jig saw is of a similar variety to those for the circular saw. As a general rule a blade with widely spaced teeth is used for rough, fast cutting of timber. For fine or cross cutting of timber a blade with teeth set well together is used. A blade similar to the hard hacksaw type is used for metal and plastics and a knife edge blade cuts leather, rubbers and plastics.

When cutting thin metal sheet clamp it on to a backing sheet of softwood or plywood. This minimises vibration and the risk of tearing the metal. Make sure that the backing wood is soft enough to be cut with the metal blade.

Spread some lubricant along the cutting line. This stops the blade clogging and keeps it cool. Use oil for steel and paraffin or turpentine for non-ferrous metals such as copper, aluminium and brass.

It may well be that you will do enough cutting work to utilise both a circular and a jig saw.

Where only occasional cutting is envisaged the jig saw is certainly the more desirable model because of its versatility.

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