Basic power saws

Sawing by hand is usually a time-consuming and tedious task-especially if you want to make long, straight cuts or intricate curves. But with a power saw or saw attachment, this type of work can be carried out with a minimum of effort and to a high degree of accuracy.

The circular saw and jig saw (sabre saw) are the two most popular types of power saw. Both types are used to make straight cuts with or against the grain and the jig saw can also cut curves and intricate patterns. Armed with these tools you should be able to tackle most basic sawing jobs.

Attachments and integrals

Both circular saws and jig saws can be purchased either as attachments to existing power drills or as integral units with inbuilt motors. And while there is no hard and fast rule about whether an attachment is better or worse than an integral tool, it is worth considering which is more suitable for your particular needs before purchasing.

If you plan to make only occasional use of a circular saw or jig saw, then an attachment may be all you need. But for more frequent use-particularly on tough materials-an integral is a better buy.

Choosing a circular saw

Integral circular saws are generally more powerful than attachments, and so permit greater accuracy and safety. Since they are already set up ready for use, they avoid the time-consuming necessity of switching back and forth from saw to drill that using an attachment often involves.

Whether you buy an integral saw or an attachment, check first that the saw is powerful enough to tackle basic jobs around the home. The power of an attachment is of course limited by the output of the drill itself so you should study the manufacturer’s specifications carefully before buying.

Even with an integral saw most manufacturers give only the input power of any particular model-not the all important output power. Depending on the make of the saw and its efficiency the output is bound to be anything from 60-90 percent lower than the input so this should be allowed for when calculating the motor power of any saw.

A good guide to the power of any particular circular saw is the largest diameter blade that can be fitted into the machine—the larger the blade the more powerful the saw’s motor is likely to be. The smallest domestic saws have blades with a diameter of about 125mm and a motor of at least 300-450 watts. The largest domestic saws with blades 180mm in diameter need a motor of about 1000 watts to operate efficiently. Larger saws suitable for heavy-duty work are much more expensive than domestic models and if you need one for a particular job it would probably make more sense to hire one for a short period.

Many manufacturers of integral saws and attachments state the maximum depth to which their saws will cut, and this can also be used as a guide to the power of the tool. A low-powered saw with a 125mm blade can be expected to make a 30mm cut and a high-powered saw with a 180mm blade a cut 60mm deep. Remember that the depth of cut will be less if you cut at an angle or want to cut hardwood or metals.

Once you have checked that the saw is powerful enough for your needs, make sure the model you choose is comfortable to hold and use. Attachment saws should be easy to assemble and take apart. All saws should have a safety guard around the blade to prevent accidents, but avoid those with plastic guards if you want to cut metal or masonry.

Many saws can be attached to a bench -giving them greater flexibility and accuracy-so you should check that the model you purchase can be adapted in this way if you want to make use of this facility at a later date. Saw benches can prove extremely useful if you are going to do a great deal of sawing.

Parts of a circular saw

Although integral circular saws vary in design from one manufacturer to another, most have the same basic features. At the centre of the machine is a motor with a horizontal drive shaft or arbor. Flat circular blades 125mm-180mm in diameter are attached to the end of the shaft and held in place by a bolt fitted with a washer.

A spring loaded guard-made from metal or rigid plastic-is fitted around the outside edge of the blade. This comes down automatically to cover the blade as soon as the saw is moved away from the work and rises again when you start a cut in the material.

To adjust the depth of cut, a calibrated knob is mounted on the side of the machine. On many saws there is also a second knob for locking the blade at any angle up to 45° in relation to the soleplate to allow for bevel cuts.

A sole or baseplate-fixed at right-angles to the blade-rests on the work-piece during sawing to ensure an accurate cut. The blade itself is mounted 50mm-75mm behind the front of the soleplate to avoid accidentally cutting through obstructions.

Most circular saws have a detachable rip fence fitted to the side of the soleplate. This can be adjusted to guide the saw paralled to the edge of the workpiece during straight cuts.

Some circular saws are fitted with a riving knife or kerf guide. This follows behind the blade to keep the cut open and prevent the blade from snagging.

Fitting a new blade

A general purpose blade-suitable for cutting light boards—is usually supplied with the saw. Several other blades and cutting discs are available for more specialized tasks.

Before you fit a new blade, make certain that the power is turned off and that the saw is resting safely on a flat surface such as a workbench. When unscrewing the old blade you need to jam it to stop the spindle turning. To do this either jam the blade against a block of wood or—better still-push a screwdriver through the ready-made hole in the surface of the blade Then, using a suitable spanner, unscrew the fixing bolt, carefully remove the unwanted blade and lay it to one side.

When fixing the new blade into position make sure that it is fitted the right way round: almost all models cut on the upstroke, in which case fit the blade with the teeth pointing upwards. Also, make absolutely sure that the fixing bolt is threaded correctly and tightened fully. This will lessen the chance of inaccurate cuts and might prevent a serious accident occurring.

Using the circular saw

The circular saw can be used in a variety of ways; freehand or with guides for ripping or cross cutting; with the blade angled for bevelled cuts; or with a shallow set to make grooves or saw kerfs.

When using the saw-even for rough offcuts—make sure that the workpiece is secured in a vice or with G-cramps. Also check that the blade will be unobstructed beneath the work before starting the cut.

Do not start the motor and then advance the saw towards the workpiece-this is a dangerous practice which could result in accidents. Instead, rest the front of the soleplate on the workpiece with the blade clear of the surface and line it up carefully before starting the motor. Wait until the motor reaches full speed before advancing it carefully through the work.

During cutting, do not push or force the blade as this will strain the motor or cause the saw to kick back. Once the cut is complete, turn off the saw and allow the blade to stop before removing it from the cut. This will prevent the blade from catching the wood on each side of the cut and thus cause splintering. Straight cuts: For rough cuts, mark out the workpiece and use the saw freehand with the notch set in front of the sole-plate as a guide. More accurate cuts can be made using the rip fence. Adjust the fence carefully allowing for the set of the teeth on the saw. Then rest the front of the soleplate on the workpiece and check that the blade is aligned correctly before making the cut.

If the cut is too far in from the edge for you to use the rip fence, clamp a long straightedge to the top of the workpiece and use this as a guide for cutting.

Power saw blades

Circular saws

General purpose blade: This blade-normally supplied with the saw-combines the features of rip and crosscut blades. It usually has 24 points and can be used for cutting wood ctnd lightweight boards across and along the grain. Crosscut blade: Used for cutting timber to length.

Rip blade: For sawing timber along its length and parallel to the grain. Planer blade: This gives a very smooth finish – use it on hardwood and thin board.

Tungsten carbide blade: A toughened blade used to cut materials with a high resin content, such as plastic laminate and thick chipboard.

Metal cutting blade: This fine-toothed blade is used for cutting most soft metals.

Flooring blade: Not just designed for cutting floorboards, but any tough material where there might be hidden nails or other obstructions. Metal cutting wheel: Used for metals and plastics.

Masonry cutting disc: This will cut ceramic tiles, slate, marble, soft stone and non-ferrous metals. Compo and wallboard blade: A fine toothed blade for cutting wallboard and composition sheet. Reinforced abrasive wheel: For cutting marble.

Friction blade: For high-speed cutting of corrugated iron and flat steel sheeting.

Jig saws

General purpose fine toothed: Used for cutting fine wood and man-made boards-such as blockboard.

General purpose medium toothed:

For plywoods and particle boards.

General purpose rough toothed:

For rough cut wood.

Tungsten carbide tipped: Specially designed for cutting chipboard.

Special purpose blades: These are designed for cutting materials other than wood, such as metal, stainless steel and plastic.

Flush blade: This sticks out from the front of the jig saw so that you can cut right up to obstructions.

Scroll blade: Used for cutting tight curves and intricate shapes. cuts and might prevent a serious accident occurring.

Using the circular saw

The circular saw can be used in a variety of ways; freehand or with guides for ripping or cross cutting; with the blade angled for bevelled cuts; or with a shallow set to make grooves or saw kerfs.

When using the saw-even for rough offcuts—make sure that the workpiece is secured in a vice or with G-cramps. Also check that the blade will be unobstructed beneath the work before starting the cut.

Do not start the motor and then advance the saw towards the workpiece -this is a dangerous practice which could result in accidents. Instead, rest the front of the soleplate on the workpiece with the blade clear of the surface and line it up carefully before starting the motor. Wait until the motor reaches full speed before advancing it carefully through the work.

During cutting, do not push or force the blade as this will strain the motor or cause the saw to kick back. Once the cut is complete, turn off the saw and allow the blade to stop before removing it from the cut. This will prevent the blade from catching the wood on each side of the cut and thus cause splintering. Straight cuts: For rough cuts, mark out the workpiece and use the saw freehand with the notch set in front of the sole-plate as a guide. More accurate cuts can be made using the rip fence. Adjust the fence carefully allowing for the set of the teeth on the saw. Then rest the front of the soleplate on the workpiece and check that the blade is aligned correctly before making the cut.

If the cut is too far in from the edge for you to use the rip fence, clamp a long straightedge to the top of the workpiece and use this as a guide for cutting.

Circular saws

General purpose blade: This blade -normally supplied with the saw-combines the features of rip and crosscut blades. It usually has 24 points and can be used for cutting wood <*nd lightweight boards across and along the grain. Crosscut blade: Used for cutting timber to length.

Rip blade: For sawing timber along its length and parallel to the grain. Planer blade: This gives a very smooth finish – use it on hardwood and thin board.

Tungsten carbide blade: A toughened blade used to cut materials with a high resin content, such as plastic laminate and thick chipboard.

Metal cutting blade: This fine-toothed blade is used for cutting most soft metals.

Flooring blade: Not just designed for cutting floorboards, but any tough material where there might be hidden nails or other obstructions. Metal cutting wheel: Used for metals and plastics.

Masonry cutting disc: This will cut ceramic tiles, slate, marble, soft stone and non-ferrous metals. Compo and wallboard blade: A fine toothed blade for cutting wallboard and composition sheet. Reinforced abrasive wheel: For cutting marble.

Friction blade: For high-speed cutting of corrugated iron and flat steel sheeting.

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