- Motor and gearbox
- Blade fastening and pendulum mechanism
- Jigsaw sole structure
- Body shape
- Additional equipment and special functions
At first glance, all electric jigsaws are the same, but there are a number of design features that distinguish a professional tool from a household one. Using the example of the most successful solutions in modern models, we will introduce readers to these specific differences..
Motor and gearbox
Traditionally, jigsaws, like other power tools, are equipped with brushed AC motors. There are, however, other variations – with brushless motors, but this feature is typical for most of the professional and industrial grade tools. The advantage of a brushless motor is a smooth starting system, low noise level and accurate speed control, which is very important for a jigsaw, especially when cutting all kinds of materials. The collector motor has a power supply system in which the speed is regulated by limiting the stroke of the button, which does not provide sufficient accuracy.
On average, the power of both types of motors ranges from 100 to 800 kW, which roughly corresponds to the thickness of the cut wood blanks from 10 to 120 mm. At the same time, the practical minimum for a household tool is 350 W, and jigsaws with a power of over 600 W can only be used in conjunction with reinforced blades that can withstand such power. The rotor speed parameter for most jigsaws is not regulated, instead, the pendulum stroke frequency is indicated, which can be 3500 strokes / min and adjustable in the range from 800-1000 strokes / min.
A unique feature of the jigsaw drive end is the forward gear reducer. Unlike other technical analogs, this unit does not have a crank mechanism as such, because the lateral inclination of the connecting rod in this kinematic scheme is unacceptable. Instead, a linear actuator on two sliding assemblies is used, driven by a transmission consisting of a push rod and a yoke rocker. The reliability of this unit depends on the correct choice of a friction pair, otherwise one of the elements will gradually wear out. You should also pay attention that when the tool is shaken vertically, no clicks are heard in the gearbox – this phenomenon indicates that the pendulum pusher is dry, that is, it has no lubricant.
Blade fastening and pendulum mechanism
At the bottom of the pendulum there is a saw blade attachment point. Most jigsaws are designed to use European T-shank saws, but U-seated tools can be found if desired. The point of such a purchase is that such saw blades are less common, and therefore the likelihood of meeting a fake when choosing expensive consumables is slightly lower.
The system itself of fixing the blade in both cases may require the use of a tool, or be toolless – the so-called fast-fix clamp. In the first case, it is better to give preference to models in which the clamping screw has a slotted head for a hexagon or a Torx wrench. For quick-release saddles, the wedge-type locking mechanism is considered optimal..
In the same part of the jigsaw there is a blade support system. In most popular models, it is represented by a roller with a central groove. This is a fairly simple mechanism that captivates with its cheapness, but it is not without its drawbacks. First of all, because the width of the canvas is different for the canvases, which means that at least the groove should have a V-shaped profile. But even this does not provide reliability: such a mechanism itself has a backlash, moreover, over time, the groove deepens and it becomes more difficult for the roller to rotate, up to the final jamming. Therefore, it is better for professionals to give preference to tools with a fork mechanism (Bosch GST 160, Festool PS 300), but always with an adjustable cheek opening. Such a support system is also better in that it limits the sawing off at the lowest point, which not all roller stops can boast of..
The pendulum mechanism has a longitudinal swing function, when turned on, the saw performs not only reciprocating, but also oblique vibrations, cutting either the lower or the upper edge of the material. Almost all tools have this ability, however, only professional (Hilti, Festool) have more than three positions for adjusting the swingarm stroke and, due to a more reliable design, allow an accelerated curvilinear cut when swinging is on..
You should also pay attention to the working stroke of the pendulum. In most models, it does not exceed 30–40 mm, however, the higher this figure, the more teeth will be involved in the work, which is especially important when cutting metal and thin materials. You also need to remember that the effective cutting depth is not determined by the length of the blade, but by its protrusion above the sole at the top dead center.
Jigsaw sole structure
During operation, the jigsaw experiences vibrations, so the design of the sole should not only ensure confident movement of the tool, but also help to save the surface of the material being cut from scratches. This part of the structure can perform a number of other functions..
So, most jigsaws have the ability to adjust the tilt of the blade at an angle other than 90 °. In the simplest case, the base of the body has a semicircular seat, in which the sole turns freely after unscrewing the pressure screw. Professional models (Black&Decker KS901) have fixed positions at 0 °, 45 ° and 22.5 °, and on the Mafel P1CC industrial jigsaw, the inclined sole is removable, while it can be adjusted to extend in the longitudinal direction. This, by the way, is one of the least obvious nuances in terms of the configuration of the sole: if it is pushed too far forward, it may be difficult to trim in the corners..
The sole of the jigsaw can be made of die-cast aluminum or stamped steel. In the latter case, with insufficient metal thickness, deformation of the front protruding skis is possible, especially with high tool power. Aluminum soles are most commonly found in jigsaws that have a built-in chip removal system through channels in the base. On many jigsaws, the sole is equipped with soft plastic overlays to ensure the safety of the material and absorb vibration. Also, in the aluminum base of the tool, there may be longitudinal grooves, which can be called an unambiguous plus: sawdust is quickly removed from the contact zone and does not scratch either the part or the sole itself.
The jigsaw can have two body versions. Classic implies the presence of a D-shaped handle, which is typical for most budget models. This form factor is most convenient when working with a jigsaw in non-standard positions: due to the increased length of the lever, the tool is easier to keep in the cutting line. However, the rest of this design is unremarkable and even has some disadvantages..
An alternative shape of the body is called mushroom and implies the presence of a protrusion in the front, which acts as a handle to hold the tool with the other hand. The main grip is performed on the engine shell housing. In this case, the clamping force is very close to the cutting area, which provides the best control over the tool in a horizontal position. However, this version of the case has its own specifics of work..
First, the power button is permanently fixed, which does not allow you to quickly turn off the tool in the event of an emergency. Secondly, it is impossible to smoothly increase the speed when the button is pressed, which is not always convenient, plus jigsaws with such a body shape can be completely inconvenient for left-handers.
Additional equipment and special functions
Like most woodworking tools, jigsaws are supplied with accessories. Of the most common, one can distinguish a parallel stop, due to which it is convenient to cut slats of a fixed width from sheet materials. Some stops can be supplied with a scale with millimeter markings. Also from the standard equipment, the most widespread compasses and adapters for sawing on a guide rail.
If the jigsaw does not have a standard plastic cover, it can be purchased separately, but the ability to make threaded holes in the sole is required. Some overlays have a narrow slit in the blade area to help reduce chipping. Also, for many models you can find on sale anti-splinter pads installed in a special groove in the sole. The cut area can also be protected by a polycarbonate screen, which is intended not so much to protect the eyes from chips as to optimize the operation of the chip removal system.
Some tools have a laser pointer for cutting direction, which is very convenient. Of the least obvious features, one can single out the device and the location of the air outlets from the engine compartment, often they contribute to the raising of dust and getting it into the eyes of the operator. The most controversial feature is the ability to enter the blade without drilling: this is a useful feature, but not every tool has a proper performance.