Handheld, power circular saws

A handheld, power circular saw is one of the most useful tool which a person can own.

For making straight cuts in timber or manmade board, it is much easier than using a handsaw and will give a better edge if the correct type of guide is used.

As well as just cutting timber to size, it can be used for:

• cutting rebates
• cutting mitres or chamfers at any angle up to 45 degrees
• cutting wood away to start off a slot
• cutting through tongued-and- grooved floorboards

A wide range of saws are on the market and it is worth knowing the basic options before you look to buy one. Most circular saws have the same set of features: what varies is how the manufacturer has incorporated them into the saw and how easy they can be used.

1. Blade 2. Blade guard 2a. Riving Knife 3. Rip guide 3a. Rip guide lock 3b. Notch guide in sole plate.	4. Vacuum attachment 5. Depth adjustment 5a. Tilt adjustment 6. Second handle

Sole Plate:

The sole plate is the bottom of the saw which seats on the surface being cut, it usually has a turned up lip around the edge so that it can move smoothly over the work surface. The motor is fixed to the top side as is (normally) the rip guide locking mechanism. A slot in the sole plate allows the saw blade to project on the underside.

Wattage (or the power of the motor):

The more powerful the motor fitted to a saw, the bigger jobs you can do. Motors range from about 500W to an more than 1,500W. Generally speaking the larger the blade and the deeper the cut, the high should be the wattage.

Blade: (1)

The size of blade supplied with a saw will vary, from below 150 mm dia to over 250 mm dia. The size of fixing hole in the middle of the blade also varies (from about 12.5 to about 30 mm). So blades are not fully interchangeable between models due to the differing overall diameter and that of the mounting hole. The size of blade is less important than the maximum depth of cut which limits what you can do. Generally the larger the bore hole, the better grip between the motor and blade. You will not be able to fit a larger blade (as it will not fit in the blade guard) generally you should not fit a smaller blade.

Most saws are now provided with tungsten-carbide tipped (TCT) blades, these should be able to do a lot of cutting before needing replacement. Check the method of removing/replacing the blades, if you will need to change the blade often, you need a simple method, often a bar needs to be put though a hole in the blade and a spanner (often supplied) used to remove the holding bolt (to undo the bolt, it will need to be turned in the opposite direction to the blade rotation).

Teeth:

The number of teeth determines what a saw blade is best at and the kind of finish you will get: 4 to 6 are best for rip sawing (along the grain); 12 or more are best for cross- cut sawing (across the grain).

Other types of blade (some without teeth but with a diamond impregnated rim) are available for cutting material other than timber (i.e. plastic, brick etc.).

Blade Guard: (2)

The saw should be fitted with a spring loaded blade guard which covers the blade under the sole plate, it will usually open automatically when a cut is started at the edge of a piece of timber. Sometime the blade guard will not open automatically due to the thickness of the material or when you start in the middle of a sheet (or when cutting the tongues off T&G in floorboards), the guard should have a manual control so that it can be easily opened when necessary.

If you are offered an old saw without a blade guard, it is probably best to decline the generous offer.

Riving Knife: (2a)

The riving knife is positioned behind the saw blade, it's purpose is to prevent the freshly cut timber from closing up onto the blade, The knife needs to be thicker than the plate of the saw blade and narrower than the saw cut - it must be centred on the saw blade. The front edge of the knife is curved and the gap between it and the blade should generally be less than 12mm at any point. A replacement riving knife will probably need to be fitted if a replacement saw blade which is either thinner or thicker is fitted or if the new blade is of a substantially different diameter. It will also need replacing if it becomes damaged.

As with blade guards, if you are offered an old saw without a riving knife, decline the generous offer.

Rip Guide: (3)

This allows you to cut parallel to the edge of a board or plank - typically up to around 15 to 20 cm (6-8in) away, most saws have the adjustment arm graduated so that the guide can be easily set to the required dimension. The longer the guide the better control you will have. To keep a cutting line straight when cutting beyond the range of the guide, the guide should be removable so that you can guide the edge of the sole-plate along a batten clamped to the board. Most models allow the saws to be guided using the right- hand side of the sole-plate: some have insufficient room under the motor to use the left-hand side as well.

Sometimes the sole plate has an indication of the cutting line (e.g., a 'v' notch in the front edge), this is useful if you need to cut a sheet roughly to size, you can just draw the rough cut line and cut it free hand - no matter how careful you are, it will not be very straight over any distance.

Vacuum attachment: (4)

This is usually position on the side of the blade cover, it allows a vacuum cleaner hose to be attached to the saw so that the saw dust is removed as you cut. If you intend to use a vacuum extractor, check that the size suits your vacuum cleaner-normally around 25 mm or 35 mm.

Adjustments: (5)

You should be able to alter the depth of cut (5) (generally it is best around 5 mm thicker than the material you are cutting) and the angle of cut (up to about 45 degrees in one direction) (5a).

Another adjustment is the riving knife at the back of the blade - this follows the blade along the cut. The knife needs checking when you buy the saw and adjusting or an alternative one fitted when the blade is changed. The riving knife is an important safety feature, so follow the manufacturers instruction for the particular model.

Second handle: (6)

You need both hands to hold the saw steady as you move it along and a second handle is usually provided on top/front of the saw. If you are left handed, check the feel when holding the saw with both hands.

Power switch and lock buttons: (7)

7. Main power button

7a. Power lock button

Most saws have the power switch positioned on a 'pistol' like handle at the back of the saw. Normally a power lock button (to prevent inadvertent operation of the main power switch) is positioned so that it can be operated with the same hand as operates the main power switch. Again, if you are left handed, check the feel when holding the saw with both hands.

Maintenance:

Saws normally need little maintenance other than keep it clean, check the vacuum attachment hole and the top of the blade guard as sometimes small strips can become lodged and reduce the extraction of saw dust.

Keep the air vent holes of the motor unobstructed otherwise the motor may overheat. If dry saw dust gets inside the motor, sparks from the motor brushes can ignite the dust.

If you use your saw a lot, the motor brushes will need changing, this can be fairly easy if they are accessible on the outer case. It may be justified to occasionally have the saw fully serviced so that the inside can be cleaned and any damaged bearings replaced.

Replacing the blade:
The saw may have a rotation lock which, when pressed, will lock the shaft solid so that the bolt holding the blade can be undone. Other models don't have a rotation lock, with these models, a normal method is to place a bar though the hole in the blade to sit against the sole plate - with the blade then held, the bolt can then be undone. Remember that to remove the centre bolt, it has to be turned in the opposite direction to the blade rotation - normally this is clockwise.

Using a handheld, power circular saws:

A circular saw is very easy to use but is a potential hazard with the blade whizzing around at a few thousands revolutions per minute; it is not a toy and should only be used by a responsible person. Only use a circular saw where you can see the underside of what you are cutting and know that it is clear of obstructions, you do not want to saw through an electric cable or copper pipe.

Watch out for the power cable, it can easily find it's way under the timber and you will not realise it is there until you go though it. An old trick with all power tools is to run the cable behind you and over one of your shoulders; then the cable should remain out of your working area.

When using a batten to guide the edge of the sole plate, do not use too thin a batten as it may flex sideways as you work along it. Remember that the saw blade is a fixed distance from the edge of the sole plate so make the appropriate allowance when setting up the batten. Use a piece of scrap timber to determine the appropriate distance. You may wish sometimes to set the batten on the waste side of the cut and at other times on the finished material, so you need the two distances between the edge of the sole plate and each side of the blade, otherwise you may set up the batten incorrectly and find that you have undercut or overcut the material by the width of the blade.

Only use a circular saw on material which is well supported and stable, remember that having cut though the timber, there is going to be an offcut; nothing to worry about if it is a 25 mm strip of 3 mm ply (but you will still have to hold it), but it will need full support if it is half a sheet of 32 mm ply. If the offcut is heavy and unsupported, it will twist away before the cut is complete and cause damage to the cut edge, and possible damage to the saw/ injury to the operator.

When sawing timber with a laminate finish, cut from the back. The front of the saw blade cuts in the up direction, so the laminate will be 'pushed' onto the base material and will not be damaged. Cutting from the front will result in the laminate chipping as the laminate will be unsupported when the saw blade goes through it.

Always use a face mask and goggles - for people who will generally ignore this aspect of safety - a face mask is an absolute necessity when cutting MDF, the glue used in the manufacture of MDF is dangerous if inhaled.