Saws have teeth which are measured as points per inch. The number of tooth points per inch is always one more than the actual number of teeth per inch (tpi), since any measure of whole teeth will always include the point of the next tooth. Rip saws have larger teeth with somewhere between 4-7 points, compared to say, a dovetail saw, which may have 20-24 points. As the number of points increases so does the precision cutting obtainable with a saw.
The teeth on saws are 'set' meaning that they are bent out slightly to either side of the blade in an alternate pattern along its length. This prevents the blade from becoming stuck in the timber by making the cut slightly wider than the blade. Some saws used for finer work may have a blade which is tapered to become narrower above the teeth to achieve the same outcome. Some modern hand saws have hardened teeth which means that unlike traditional saws they cannot be sharpened and are useless once blunt.
These saws have long blades to around 65-70cm (26 – 30 inch). They are designed to cut timber along the grain. The relatively large teeth on the blade have a chiselling action which cuts out small chips of wood, and so cutting is done to the waste side of the cutting line. The front of the teeth are set at 60-90 degrees (typically, 90°) in relation to the cutting edge, where 90 degrees provides more 'hook'. The smaller teeth towards the tip of the saw blade are used to create a 'kerf' of enough depth to enable the saw to be pushed forward in the same position.
(Note: The kerf is the cut and is measured as the width of the cut, which is the distance from one side of the saw teeth to the opposite side.)
The blade is then drawn backwards in a long sweeping movement whilst maintaining an angle between the blade and the timber of at least 60 degrees so as to avoid making long cuts through the wood. These days, there is less use for a rip saw since most timber is already cut to the right width, and circular saws can also be used for the same purpose.
Cross Cut Saw
These are so-called because they are used to cut across the grain e.g. cutting boards to length. They are usually a similar shape to rip saws though usually not as long. The blade teeth are more pointed and have a bevelled edge on the front and rear. The front of the teeth is set at 75 degrees to the cutting edge, and they vary between 5-12 teeth per inch.
The saw is drawn backwards on the timber to start cutting. The angle between the timber and the saw does not have to be as great as with a rip saw.
These are basically cross-cut saws of a shorter length (60cm or less). They are used for finer work and as such they have smaller teeth and there are generally more of them per 25mm (1 inch) (10-12).
The tenon saw or 'back saw' has a blade which is stiffened with a solid brass or steel casing around the top edge. The blade is thinner than the saws discussed so far and needs this additional support to prevent it from buckling. They usually have somewhere between 10-14 teeth per inch.
The blade is typically 20-40cm (8 – 16 inches) long and they are used for finer work e.g. cutting mitres. The original versions were designed only for cutting mitres and their blades had flat edged teeth for cutting along the grain. Nowadays they usually have bevelled teeth so they can be used for cutting across the grain too.
This is really the same as a tenon saw, and refers to the smaller types with shorter blades, more teeth per inch, and a straight grip handle (of turned wood in the older versions), which enables it to be used for even finer work.
Also known as a 'turning saw' (or frame saw), the bow saw is used mainly for cutting curves. As such it has a narrow blade which is set in a frame under tension. Tension is adjusted by means of tightening either bolts or a twisted string or cord which runs parallel to the blade at the opposite end of the frame. The angle of the blade to the frame can also be adjusted by twisting the handle and a knob on the opposite end of the frame adjacent to the blade. Caution should be used to ensure that the blade is not twisted before use when doing this.
The coping saw or 'scroll saw' is also used mainly for curvature work. It has a very fine blade which can be detached and pushed through a hole before being re-attached. The handle may be tightened to increase blade tension. The blade can be set to any angle against the frame for cutting.
Also referred to as a keyhole saw, this is a longish narrow saw blade which tapers to a fine tip and is attached to a straight grip handle. It was designed for cutting out keyholes, but can be used for cutting out circles or other shapes enclosed within a piece of timber. A hole is first drilled through the timber to allow enough room for the saw tip to pass through.
This is similar to the pad saw but with a slightly larger blade and is used mainly for cutting curves on flat boards.
A good quality power saw can save a lot of hard labour from using hand saws. The types of cuts that can be made with wood using a power saw are almost limitless, and power saws may be used for jobs ranging from garden bed retaining walls to kitchen spice racks. The blades for different types of saws are available in various sizes and strengths, depending on the type of wood that is to be cut and the accuracy required. However, some power saws are not suitable to more refined work where greater control is needed.
Some of the more widely used power saws in carpentry are as follows:
- Circular saw - these are hand held electric saws which as the name suggests have a circular blade. The blade is held within a housing so that only part of it extends outwards for cutting (from as little as an eighth of an inch), and it spins at high speed. Smaller versions have blades around 160mm (6½ inches) diameter, whereas larger ones are around 235mm (9 inches). Blades between 20cm to 25 cm (8 and 10 inches) are mainly used in industry since they are less mobile saws. The angle of the base plate can be adjusted to between 45 and 90° making it possible to cut bevelled edges. Blades with fewer teeth may be used for ripping boards whereas those with more teeth are used for finer cuts.
- Bench saws - these are something like a circular saw built into a work bench. They have circular blades and the amount they protrude may be adjusted, as well as the distance of the blade from the fence or guide.
- Jig saw - these have a reasonably small blade and can be used for finer work such as cutting out shapes from boards and creating curves. A hole will need to be bored through a board in order to insert the blade for enclosed cutting.
- Chainsaw - these have no place in carpentry except for chopping up logs which may later be ripped down and seasoned.
- Band saw - these are usually stationary saws though smaller versions for sitting on the workbench are available. They have a blade in the form of a metal band with teeth on one edge and are rotated at high speed around two cogs or wheels. They can be used for intricate cuttings such as cutting curves and shapes.
- Mitre saw - also known as a drop saw or chop saw. These are used to cut across the grain of timber. They may be used for straight cuts or angled cuts. the timber is held against a fence and a powered circular saw blade is pressed down onto it from above. The angle of the blade may be changed through 1° intervals. Various type of mitre saw exist which enable different types of cut e.g. wider cuts, vertical and horizontal cuts.
Knowing What To Use and When
Being able to choose the right equipment, and to use it correctly is vital to doing the job at hand safely and successfully.
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