Wednesday 11 November 2009
Part two of Matt Long's guide to getting a basic tool kit together
So, you've measured up your timber and you know what you are going to make. Chances are, before you do anything else, you are going to have to cut your stock to length or even width so now's a good time to tell you about the saws you will need for your basic toolkit.
The basic cut
The most common cut a woodworker will do by hand is the crosscut. Here a saw is needed that will cut perpendicular to the direction of the grain. You are slicing across the wood fibres, not with them. I'll mention saws for cutting with the grain, rip saws, a little later.
The basic construction of saws does not vary: you have a thin metal blade, along one edge of which are shaped teeth which cut the timber. The blade is narrower at the front and wider at the rear, where a handle is attached. In the crosscut saw, the teeth are triangular shaped, and chamfered, so that the tip of the tooth is a point. The teeth are set, which means they are bent ever so slightly outward, alternating to one side of the blade and then the other, with the sharp point of each tooth to the outside. When cutting, the teeth cut through the fibres on either side of the kerf (the slot cut by the saw), and the timber in between crumbles away.
This also means the kerf is just wider than the blade itself, preventing the blade from jamming in the cut. The saw also cuts predominantly on the push stroke.
Crosscuts come in different sizes for different jobs. My old Disston handsaw (see photo 1) has around seven teeth per inch (tpi). Years ago, when an apprentice joiner, the Disston was the saw of choice, and would easily plough through anything from joists to stud framing with ease.
A panel saw is just a handsaw with a higher tpi, typically above 10 (see photo 2). As its name suggests, the saw is usually used for cutting thinner timbers such as panels, and plywood. The higher tpi and subsequent tooth and kerf size helps to minimize any spelching on the cut for finer timbers.
My panel saw was something of a workhorse on site, too... it was excellent for finer joinery, including cutting mitres on skirting boards, dado rails, etc.
Rip saws are designed for cutting along the grain of the timber, rather than across it. They have the same basic construction as cross cuts, it is just that the shape and size of the teeth is different. Whereas crosscut saws are shaped to a point, (see photo 3) the rip saw teeth do not have a chamfer and are sharp across the width of the blade, more like a chisel (see photo 4). This means the timber is removed in tiny shavings across the width of the kerf, rather having the edges cut and the timber in the middle crumble away. This is necessary because a crosscut saw is relatively inefficient when going with the grain, as timber does not crumble as well between the edge cuts of the kerf.
The backsaws are for very fine carpentry, and they include the dovetail, tenon (see photo 5) and gent saws. The blade of a backsaw is rectangular, and thinner, to allow for finer cuts and more teeth per inch. Because the blades are thinner they need more support to stop them flexing on the push stroke. The saws therefore have a reinforcing back on the saw blade, hence the name. This back is usually made of brass. Tenon saws tend to be larger than dovetails, which are larger than gent saws (see photo 6), which have a different handle shape.
A keyhole saw has a much narrower blade. The function of the saw is to cut into thin materials, often panelling, for small, awkward cuts.
By far the biggest recent development in sawing technology has been the advent of the hardpoint (see photos 7, 8, 9, 10). These are cheaper saws, not intended to be re-sharpened, that have their teeth hardened. In modern saws this is usually by induction heating, basically an electric current is used to heat up the teeth, which are then cooled rapidly to leave them hard, but brittle.
Saw manufacturers are trying ever more exotic ways of designing these saws, and are taking inspiration from the East in that the teeth are ground to cut on both the push and pull strokes, increasing the efficiency of the blade, these teeth are often precision ground to produce the best cutting results. Be warned, however, the teeth are often longer and thinner and, being brittle, can easily break off when used on hardwoods.
The basic idea here is that a frame saw holds the blade in tension. This allows a blade to be much smaller, as they will not bend during use. The blades are expected to break or dull over time, when a new blade can be fitted into the frame and the saw can be used again.
The coping saw (see photos 11-12) has a particularly thin blade and is used to cut curves and scrolling patterns. The frame is designed to be relatively far from the blade to give the woodworker room to manoeuvre the blade and frame around the workpiece, and the angle of the blade can be changed for the same reason.
Hacksaws (see photo 13) are frame saws but are designed to hold blades that cut through metal, rather than wood, every toolkit needs a junior hacksaw, and the full size version.
You never know when you might need to be cutting materials other than wood.
Bow saws also follow the same general design, but they are a lot larger, and the blades have much bigger teeth as they are used to cut through green timber, so, not a necessity for a tool kit, but if you have the money, worth investing in.
Push or pull
Japanese saws (see photo 14) are becoming more and more popular in the west for quality woodworking, because of the fineness of their cut. The teeth cut on the pull stroke only, rather than the push stroke, so the blades are much thinner, as they are in tension when the teeth are cutting. This isn't the place for a detailed analysis, there are so many different varieties, but the saws come with rip and crosscut teeth. One version of the saw, the ryoba, even has both kinds. Some saws have a stiffening back rather like a backsaw, and others don't. If you are intending on doing a lot of very fine joints with a handsaw, such as dovetails, then it would be well worth investing in one of these. Western manufacturers are cottoning on to the benefits of the Japanese way and are manufacturing hybrids, trying to enjoy the best of both types of saws (see photo 15).
To finish, it has to be said the number of saws on the market these days is quite bewildering, but if you include the above saws in your toolkit, you'll be prepared for most jobs.