Some often ask us about the various differences between band saw blades and tell us how difficult it is to find the right blade. Many ask for a "universal" blade for cutting different materials at an affordable price. An arduous undertaking, but to answer all these questions and many others, we first try to understand the structure of the bimetallic blade. C onsidering that the life of a blade does not depend on the number of cuts dealt with but on the hours of work that the blade has to sustain.
The BIMETALLIC blade has: a bearing body in spring steel (50HRC) and a thread in HSS -CO super rapid steel (67-69HRC), which will be laser welded.
Once this bimetallic body has been obtained, the teeth are milled and calibrated. In this last phase the teeth are deformed laterally, in order to reduce the friction between the body and the piece to be removed, thus creating a groove suitable for cutting during the advancement of the blade, and dispersing the heat that is created.
Subsequently to this process, the blades created go through a hardening and tempering, in order to give hardness and elasticity to the material according to the size and type of geometry of the tooth.
Contrary to popular belief: the higher the hardness of the cutting edge, the greater the fragility and the lower the resistance to impacts in case of incorrect use.
An important aspect to take into consideration when purchasing the correct blade for the type of use we are going to do is the geometry of the tooth . The degree of rake (zero or positive) or of the reinforcement, given by the geometry of the tooth itself, is used to identify the blade that will be used according to the material to be removed rather than another blade.
Let's take a small example:
- a tooth with a zero threshold will be more suitable for small cutting sections;
- the positive threshold angle will instead be more suitable for heavy work and for larger cutting sections.
- the Pro Reinforced rake and the Trapezoidal one are also indicated for the removal of heavy materials. Being able, thanks to the geometry of which they are formed, to remove the chip created in a more homogeneous and constant way, guaranteeing high cutting performance.
As we mentioned earlier, the toothing is decisive for the type of application of the blade. The harder the material to be cut, the more the distance between the teeth is shortened and their number increases; vice versa, on the other hand, to cut “soft” materials, blades are used that have fewer teeth, placed at a greater distance from each other.
Some of our customers complain that numerous blade breaks often occur with a new blade, or that even the blade is new and fails to remove and cut the workpiece. In reality, most of the breakages or malfunctioning of the metal bands is given by the bad use of the blade in terms of speed, pressure on the piece and material to be removed.
An aspect neglected by many is the running-in of the blade which serves to improve its performance, guaranteeing efficiency and durability. This is because a new blade is perfectly sharp and therefore more prone to chipping under pressure and high speed. This running-in process is a quick and easy process, it doesn't take a lot of time. (To perform a correct running-in and tensioning of the blade , read our dedicated article).
Another element to consider is the emulsion of cutting oil to ensure a longer life of the blade in order to keep it cool during use, creating less torsion, reducing heat and reducing friction. The emulsion must not be excessive since a high use could invade the flywheels and therefore make the blades slip, creating an additional risk factor for the operator.
So, returning to our initial question, how can we choose the most suitable blade?
There is no real rule but we can identify how the blade with identification M42 ((8% Co) hardness 67-69 HRC), with the various teeth depending on the required characteristic, is the best compromise for cutting the most common steels. and of the different types, in all workshops and not only where you have a single cutting machine on which you have to make cuts of different materials without being able to replace the blade each time, cutting boxed, round and small squares, bundle cuts etc ..