Last week, we posted an excerpt from Charles Platt’s new book, Make: Tools. In that installment, Charles discussed miter boxes and how to cut precise angles using them.
In this excerpt, one of the many tool “Fact Sheets” that end the project chapters in the book, Charles takes a brief look at various types of handsaws, saw styles, how they cut, and basic power vs. handsaw considerations.
You can read my review of Make: Tools on Boing Boing here. -Gareth Branwyn
Some Saws and Their Teeth
Figures 1 through 6 show a variety of handsaws, each with its particular advantages.
Figure 7 shows the teeth of four of the saws in closeup. A saw with wider teeth generally cuts more quickly and aggressively, but is more likely to leave rough edges. However, the shape of the teeth is even more important.
The geometry of saw teeth has changed radically over the past couple of decades. Closeup A shows the (rather blunt) teeth of the old 26″ panel saw. Closeup B is of the modern panel saw. Closeup C is of the utility saw, in which the darkened teeth indicate that they have been hardened. Closeup D is of the small Japanese- style pull-saw.
Pull or Push?
When using a Western-style saw, you push it to cut the wood. This requires the blade of the saw to be relatively thick, so that it doesn’t bend under pressure. Or, in the case of a tenon saw, a thin blade has a thicker bar along the top edge, to stiffen it. Unfortunately, this prevents the full length of the saw from sliding down through a wide piece of wood, and limits the extent of a cut.
A Japanese-style pull-saw cuts when you pull it toward you. Because you are pulling it instead of pushing, the blade can be thin, and its lack of a stiffening strip allows it to penetrate all the way into a cut. Some people feel the Japanese saw is less effective for doing heavy work, and if you pull the saw all the way out of the wood, there may be a slightly greater risk of hurting yourself. Personally I think it’s just a matter of what you are used to.
How a Saw Works
Figure 8 shows two teeth of a western-style saw being pushed from the right toward the left. Each tooth of the saw is like a tiny knife blade, digging into the surface of the wood and kicking some of it out as sawdust. (In the case of a Japanese-style pull-saw, the blade would be pulled from the left instead of being pushed from the right.)
If you inspect a saw from the end, you’ll see that alternating teeth are angled out to either side. This set (the distance off-center) creates the kerf (overall cut width) and is shown in Figure 9. Because the teeth stick out, they make a cut that is slightly wider than the body of the saw, so that the saw can slide freely.
A hacksaw, shown in Figure 10, is designed to cut metal. The frame can be adjusted to accept blades 10” or 12” in length, and blades are available with a variety of teeth per inch, 18, 24, and 32 being common. Because the blade is thin and not rigidly clamped, it can flex while the saw is being used. Consequently, precise cuts can be difficult.
Saws that Cut Curves
Various saws that cut holes and curves are discussed in the “Holes and Curves Fact Sheet” in Make: Tools, page 164.
Protecting a Saw
Even a saw that has hardened teeth is easily damaged by banging it carelessly against steel, stone, or concrete. A saw should be placed where it won’t be knocked onto the floor accidentally. If you live in a moist environment, protect saws from rust by rubbing oil over them with a rag, or (better) use a wax such as Glidecoat that is formulated for the purpose.
Handsaws vs. Powered Saws
For more details on powered saws, see the “Power Tools” section of Chapter 20, “More Tools,” in Make: Tools, page 234. Here’s a quick summary of their relative advantages.
- Less expensive.
- No concerns about flat batteries or long extension cords.
- Small handsaws are ideal for delicate detail work.
- Very little risk of making a deeper cut than you intended.
- Unlike a circular saw, a handsaw doesn’t throw dust up in all directions. You don’t need a mask (unless you are sawing materials that create toxic dust), and there will be relatively little cleanup.
- A handsaw doesn’t make significant noise (no hearing protection needed).
- Can cut much faster.
- Much less tiring to use.
- Powered miter saws and table saws can make very accurate, precisely vertical cuts.
- Blades are replaceable for a fraction of the original cost of the saw.