Of all the hand-held power tools, there is hardly another that is as functional and yet as versatile as the jigsaw blade. It is the only one that can cope with operations of curvilinear and complex straight cuts of materials of the most different hardness, ranging from wood and, up to alloy steel.
However, the tool owes such capabilities not only to its technical characteristics but largely thanks to its consumables – saw blades.
The German manufacturers of jigsaw blades created a testing team on the basis of the Selbst company and tested all known and available for purchase saw blades in the retail network. Immediately the result was revealed that those blades that were qualitatively sharpened, had impeccable shape geometry and underwent heat treatment were an order of magnitude better than the raw metal forgings.
The second factor worthy of interest turned out to be the non-guaranteed cleanliness of the saw from the value of the saw blade. This is also true for bimetal blades, which do not have any fundamental advantages.
The method of laser welding a carbide cutting edge to the relatively soft and flexible metal of the base of the blade used in their manufacture only offers greater resistance to wear when sawing hard materials.
The third area of testing was aimed specifically at identifying the effects of tooth shape on the cleanliness of sawing wood materials, as these indicators are the most important in the work associated with the assembly of wooden furniture. Blades specifically designed for wood, with different tooth configurations, including bimetal blades, were selected.
The modification of the teeth with each pair pointing downwards in opposite directions is specially designed to make quality cuts with the lowest chipping.
The evaluation took into account the cleanliness of the cut of both the lower and upper surface of the material to be machined.
The best quality sawing results were achieved with the pendulum stroke turned off and a smooth plunge at moderate speed into the machined surface. In such conditions blades with the shape of perpendicular section in the form of a cone proved to be optimal, and this was achieved not due to the teeth of the blade being set, but due to the special way of their sharpening – along the back angle.
This sharpening is performed alternately on the right and left sides in the course of the denser movement, which prevents jamming and provides the necessary free movement in the space to be sawn.
In all tests, there were absolutely more chips on the bottom side of the kerf than on the top. The ratio was the same with all blades.
The test also showed that the quality of the cut was independent of the technical features of the jigsaws. Whether using expensive or relatively inexpensive tools, the test results depended only on the quality of the saw blades.
The HCS carbon steel saw blades – an abbreviation for high carbon steel – showed the best cutting safety results. These blades broke less often at the base of the shank when making curved cuts. Overall, all of the blades tested did not pose a risk to the operator when they broke.
Not all manufacturers make them universal according to the type of shank. Thus, blades with a “T” shank are suitable for attachment to electric jigsaws from Hitachi, Makita, Bosch, AEG, Festool. Universal u-shank is used for installation into tools by Skil, DeWalt and Black& Decker.
For qualitative evaluation of cut planes we replaced their roughness by means of special device; primary visual checking results always coincided with tool measuring results.
The hardness-to-flexibility ratio of the blades was also tested and revealed the weakest point to be the transition area to the blade fastening point. This is the area where saw blade failures most often occur.
Depending on the profile of the toothed part of the blade the tests showed the following results
- The profiled tooth flutes and the machine set teeth are quite sufficient for rough cuts and provide an acceptable cutting speed, but there are roughness and irregularities on both cut surfaces;
- The corrugated tooth profile with freeze sharpening used in metal files is well suited for making thin cuts in metals and plastics. It can also be successfully used for cutting chipboard and laminated plywood;
- Freshly sharpened and set teeth of the blade allow the cleanest and fastest sawing of wooden materials;
- Specially sharpened back edge of the saw blade to a small cone without tooth setting that allows to achieve the highest precision and cleanness of cuts. For quality reasons, the performance of these blades is somewhat lower than the others.