Circular Saws: Do’s and Don’ts
The circular saw is a most useful attachment for power tools, but remember that most manufacturers’ attachments will only fit their own make of tool.
Integral circular saws, which include their own power units, perform better than saw attachments which fit on to a drill, and also avoid the delays and bother involved in fitting.
Bothcan be used freehand or in conjunction with a saw table. Greater accuracy is possible with a saw table because guides and fences can be used and both hands are free to feed and position the timber being sawn.
The ideal working speed for a circular saw blade is 10,000 ft per minute measured at the edge. The average hand-held domestic power saw cannot approach this speed and must therefore be used with great care and patience to avoid overloading the motor.
When sawing, always try to keep the motor running at full speed. Start the motor before bringing the saw into action, never while the saw is touching the work. Ease the saw forward gently. Too much forward pressure will strain the motor. There is no need to press downward as the upward cut of the blade tends to hold the saw down on to the work.
If the motor speed drops while sawing, reduce forward pressure on the tool and allow speed to increase before continuing the cut. Persistent binding of the blade indicates that it may need resharpening.
Depth of cut obtainable with a power saw is governed by the blade’s diameter.
Attachment circular saw blades are up to 150 mm (6 in) in diameter, which gives a cut 47 mm (1 and 7/8 in) deep; a 125 mm (5 in) blade gives a cut 38 mm (1-½ in) deep.
Never attempt to correct a wandering cut by twisting the blade while it is rotating — this will overload and eventually stop the motor. Before you begin, make sure there are no buriedin the timber; they will blunt the blade and cause the motor to be overloaded.
Power tools equipped with automatic cut-outs or integral saws with slip clutches reduce the possibility of overloading.
Blades and their uses
Circular saw blades are available in several types and patterns.
The combination type is suitable for most purposes, such as cutting thick or thinand with or across the grain, as well as , block-board and .
Cross-cut blades have fine teeth that cut smoothly across the grain ofand . They are also suited to cutting plywood, hardboard and .
Rip blades, by contrast, are made for coarse cutting with the grain
The planer blade, which has no sideways set to its teeth but relies on deep, widely spaced gullies for clearing away waste, gives a neat cut and will saw a variety of thick or thin materials. It is vital to keep planer blades sharp and running at maximum revolutions, to avoid clogging and motor overheating.
Sharpening of circular saw blades is best left to experts. Most local tool shops will arrange for this; and if your saw is in frequent use, spare blades are useful. Most makers will, for a small charge, exchange blunt blades for sharp ones.
Adjusting and setting
Always set the saw blade so that its teeth will just penetrate to the other side of the timber you are sawing through. This depth-of-cut adjustment is made by raising or lowering the hinged sole plate of the saw attachment.
The sole plate is also hinged to tilt from side to side, allowing cuts to be made at any angle between 45° and 90°. The depth of saw-cut is obviously at its maximum when the blade is cutting at 90° and at its minimum when cutting at 45°.
Before starting work, ensure that the self-adjusting curved blade guard is working properly. In use it should cover every part of the blade which is not actually in contact with the work. Do not buy a saw attachment that is not fitted with a blade guard.
Adjustable guide fences, which can be set to keep the saw-cut parallel to one straight edge of the timber you are cutting, are also included on most saw attachments.
After making a few trial cuts on a waste piece of timber, to ensure that you will cut to the width required, tighten down the fence retainingfirmly to prevent vibration from working it loose.
These three basic adjustments for depth, angle and width of cut should always be made and checked before cutting begins.