How Do Jigsaws Work?
If you’re like me, you sometimes spot unusual things around you and wonder what they’re about. For example, how do they cut a hole in the tile or cut curved tile to work around a toilet or bathtub?
The answer is jigsaws. (Not the kids’ puzzle.) A jigsaw is a family of power tools that work well for cutting curves and bevels. You can also cut regular right angles, cable holes, and etched patterns.
The saw itself looks more like a sewing machine, except that it has an easy-grip handle — the slim blade cuts by swiftly moving up and down.
On either side of the blade, there’s a supporting platform called a ‘shoe.’ The position of the shoe depends on your cut. For example, bevel cuts need you to put the shoe at a 45° angle and requires a special kind of ‘pivoting shoe’ that can be swung at the required angle. Whatever you’re cutting, hold the shoe firmly against the wood. This prevents excess vibration that can spoil your cut or damage your blade.
A jigsaw can cut a variety of materials, including sheet metal, wood, metal, tile, and laminate.
Under Your Jigsaw's Cover
To create the up-and-down movement, the blade is attached to a motor and has its own gears. The positioning of the gear cogs is off-center to enable a circular motion which translates into the blade moving up and down.
Older jig saws did a straight cut where the blade went up and down. Newer saws offer orbital action which causes the blade to angle forward on the upstroke, enhancing its cutting ability.
Unlike regular saws, the teeth on a jigsaw blade face upwards. This means the cutting force is on the up-stroke rather than the down-stroke. So if you want a clean cut, you have to place your saw on the underside of whatever you’re trying to cut. Either that or turn your cutting surface upside down. This is workable if you’re cutting a single plank or slab – not so much if you’re working on a wall.
Another reason for your inverted cut is to maintain aesthetic quality. If you make a front-facing cut, the surface of your sawed material may chip (for tile), crack (for metal), or splinter (for wood). Turning the surface makes your work easier, and gives a more professional finish. Meanwhile, some types of jigsaws have scrolling heads, which allows the blade itself to rotate, essentially changing the direction of your cut without spinning yourself or your work surface. This is helpful for intricate lines and challenging cuts, like if you’re cutting a flower shape.
Types of jigsaw cuts
Say you’re moving towards the door as you cut, and you want to make a ‘corner’ or curl your cut. You’d probably have to move to the other side of your cutting surfaces, or maybe change the direction of your body. The scrolling head lets you rotate the blade instead, without moving yourself, the jigsaw, or the surface you’re working on. Only the blade turns. It’s helpful for if – for instance – you’re cutting out words, or decorative murals.
Another example is a ‘plunge cut.’ Plunging may means digging your saw into the middle of a surface and cutting from there. (As opposed to the usual technique of cutting from one end to another.
And while your jigsaw can make all kinds of versatile edges, there are times when you want to keep it simple. If all you need is a straight line, you can use a fence. It’s a kind of guide (mostly made of metal) that lies parallel to your blade for creating straight cuts. You clamp the fence in place, and it keeps your blade straight, maintaining the accuracy of your cut.
Jigsaws are not as good for long, straight cuts. Circular saws are a better choice for long straight cuts.
Consider blade type and cutting speed.
As you shop for a jigsaw, think about the types of things you’ll be cutting. Differing materials require tailored blades – options include narrow double-edged blades and wider flush cut blades. You want to get the right blade for the task.
In addition to the wood blade, you can also get sheet metal blades, fiberglass/fiber-cement blades and ceramic blades. Bi-metal blades are best for metal-cutting.
You want a jigsaw that allows you to swap blades easily, and has a variable speed system. The speed of your blade doesn’t just affect cutting power and ease of work. It also influences your finishing result. A faster blade can cut through harder surfaces, but it can also cause more cracks.
Best practices for using jigsaws
Ask your tool vendor about the strokes per minute (SPM) on your saw. This is the number of times the blade moves up-and-down and is sometimes called an oscillation rate. Tile cuts need a slower SPM to avoid breakage. Have a selection of blades, and see if your saw seller offers additional ones as part of your jigsaw pack. You need slim blades for curved cuts and wider ones for straight edges. Teeth size matters too. For rough, quick, initial cuts, use a blade with larger teeth set wider apart. Follow up with tight, tiny teeth for a slower, smoother finish.
Also, if you plan to use your saw on multiple surfaces, make sure you get blades tailored to cut wood, metal, or clay. The width of the teeth and the hardness of the blade differ. As a tip, when you’re cutting fine metal sheets, lay your metal between two pieces of plywood. The wood should be about an inch thick, but position it so you can see the metal you’re cutting. This reduces cutting errors, which are tricky to correct. Finally, no matter how handy you are, it helps to be careful. Wear protective gear (goggles, earmuffs), and always practice on a scrap surface first. It prevents the need for expensive replacement of botched surfaces