How to Sharpen Band Saws Correctly
Band saws are cutting tools used in band saws. They are a closed tape with teeth. They have a mass of their own advantages, characteristic only for them. Band saws leave a much smaller width than circular tools: if this fact is probably insignificant when cutting budget wood, then when cutting elite metal and cutting valuable wood species it is critically important. With their help, you can cut absolutely any workpiece. In addition, band saws demonstrate good speed, provide high quality cutting surfaces. Reducing waste chips due to their use is an obvious thing. However, in order to consistently feel in practice all of the above advantages of working with the tool, it is necessary to responsibly approach the issues of its maintenance. Sharpening of band saws, as well as their wiring should be done efficiently and in a timely manner.
The price of sharpening band saws in specialized offices is usually low, but the speed and literacy of the work is not always pleasing. Is it possible to cope with the task with your own hands? Of course, if you know how to sharpen band saws and have the necessary equipment.
Table of contents
A bit of theory: what is the tool made of?
Saws for wood are usually made of tool steel (hardness 45 HRC).
For the production of metal products, Russian manufacturers turn to B2F and 9HF steels, while foreign ones. to C 75 and others. The teeth of such saws in the process of hardening by high-frequency currents "awarded" highest hardness. Often, when working with metal, a bimetallic band tool is used: its blade is made of spring steel, and the ribbon with teeth is made of an alloy with a high content of cobalt and tungsten. This high-speed steel “joins” to the base of the saw with an electron beam.
All about the teeth and their sharpening angles
Band saws can have different tooth geometry: it is affected by the type and properties of the raw materials being cut. As for tools for working with wood, they can be carpentry, dividing and intended for sawing logs. and the parameters and shape of the teeth of each "subspecies", respectively, are different. The angle of sharpening of band saws on wood is determined by the manufacturer on the basis of a number of factors, but the key trend is this. the harder the material, the smaller the front angle should be.
For metal saws with a constant pitch, two main tooth shapes are characteristic. standard and “positive rake angle”. Standard teeth are intended for cutting thin-walled material, with a positive rake angle. for processing metal with thick walls.
Now about the size of the step. For thin-walled blanks (sheet metal, pipes), saws with a small tooth pitch are used. otherwise there is a risk of damage or even breaking a tooth. Thick-walled materials are best handled with a small tooth per inch tool.
In order to eliminate the resonance effect, which provokes vibration of the blade, a number of saws are made with a variable pitch.
The intricacies of wiring band saws
As the tool is used, the quality of its cutting edge decreases. Therefore, the wiring and correct sharpening of band saws is a natural part of the work process.
Note! Divorce must be made before sharpening, and not after it!
Wiring is an operation to bend the teeth to the sides to prevent the tool blade from being clamped and reducing its friction. There are three main types of wiring:
classical. the teeth bend to the right and left sides strictly alternately;
cleaning. every third tooth is left in its original position. “Actual” for tools used for cutting especially hard materials and alloys;
wavy. each tooth has “its” value of the limb value, thus, a wave is formed from them. This is the most difficult type of wiring.
Worth to know! During a divorce, not the entire tooth is bent, but only a part of it — a third or two thirds of the top.
Video: How to Sharpen Band Saws Correctly
Divorce values recommended by manufacturers fall within the range of 0.3-0.7 mm. The operation is carried out using special adjustable tools.
How to sharpen a band saw?
It has been proven: over 80% of cases of tool rupture occur due to non-compliance with the rules for sharpening band saws. The need for manipulation is determined visually. by the appearance of the teeth themselves or by the state of the cut walls (increase in surface roughness).
Circles for sharpening band saws are selected depending on the hardness of the teeth. To sharpen products made of tool steel, they turn to corundum circles. Bimetallic saws require diamond or borazon samples. The shape of the grinding wheel for band saws should be determined based on the parameters of the tool. It can be profile, cup, flat, dish-shaped.
Before starting work, it is recommended to allow the saw to sag in an inverted state for ten to twelve hours.
DIY sharpening requirements for band saws:
ensuring uniform removal of metal along the tooth profile;
elimination of excessive pressure of the circle (this can lead to annealing);
ensuring the safety of the height and profile of the tooth;
mandatory presence of coolant;
control of the absence of burrs.
Standard instructions for sharpening band saws say that sharpening should be done either on the front surface of the tooth, or on the front and back. But this is a theory. In practice, many professionals, as well as folk craftsmen, “execute” it exclusively on the back surface. so, in their opinion, it is more convenient.
In general, despite the mass of rules and requirements, these tools are quite unpretentious in terms of sharpening. You can work with them, both with the help of a special tool-grinding device for band saws, and manually; apply circles with different shapes and materials, etc.
Before sharpening a band saw, it is necessary to familiarize yourself with the main methods of performing this operation.
Method 1. Full profile sharpening
It is the highest quality, produced on an automatic machine. The Elbor circle, precisely matched in shape, passes through the entire interdental cavity with one movement along with the corresponding surfaces of adjacent teeth. Obtaining angular shapes at the base of the teeth is excluded. The only drawback of such sharpening is the need to have a certain number of circles for “multidisciplinary” saws at regular disposal.
Method 2. Sharpening the edges of the teeth
It can be carried out on a professional machine or manually.
If preference is given to the machine, then, again, you should correctly select a circle. usually these are flat samples. In general, specialized sharpening equipment is recommended to be used only in cases where the amount of work is large enough. It is better to do episodic “home” manipulations manually. using an engraver or on a conventional machine. When working for safety reasons, be sure to use a mask or goggles.
If you don’t have a machine or an engraver in your arsenal, you can sharpen the band saw with the usual grandfather method. wielding a file. Three or four confident movements along the back or front face of each of the teeth. and the thing, as they say, is “wearing a hat”. With regular and diligent execution of the operation, the skill of high-quality manual sharpening will appear quickly.
Tips from professionals
1. In the case of sharpening a band saw by means of a machine, before starting work it is necessary to make sure that the grinding wheel is correctly positioned relative to the tool.
2. It is very important to remove from the sinuses such an amount of metal so that all microcracks are guaranteed to be fixed.
3. If the tool “functioned” without quality service for longer than the manufacturer allowed, the amount of metal removed in one sharpening should be increased.
4. To check the grinding results, always use a new tool as a reference.
5. Saw tooth shape. a parameter developed and verified over the years. Therefore, hoping that the tool will be sawed “like clockwork”, regardless of what you do with the teeth, is a huge mistake.
6. Subject to operational requirements, the band saw will serve you honestly until its width is reduced to a figure equal to 65% of the original value. The width decreases, naturally, in the process of resharpening.
7. There is a completely absurd recommendation that there is no particular need for deburring after processing. If you "listen" to it, then the appearance of microcracks in the canvas is guaranteed.
8. After work, the band saw should be immediately cleaned of resin and sawdust, and before sharpening, a thorough inspection. Otherwise, the risk of clogging of grinding wheels is extremely high. And this inevitably entails a “hackneyed” sharpening procedure.
What errors can occur during sharpening?
Mistake 1. Burnt tooth sinuses
The reason for this phenomenon lies in the excessive efforts of the grinding wheel. As a result. rapid blunting of the tape.
Error 2. Incorrect angle and imperfect shape of the sinuses of the teeth.
Several factors can lead to this situation:
demolition of the clown of the grinding device;
error setting the angle of the head of the machine;
mismatch of the grinding wheel profile.
That’s all. Now you know how to sharpen the band saw correctly, and what tools and accessories may be required for this.