Selecting a circular saw for rip cutting. Saw blades: educational program, features, selection tips, classification

During construction, repairs, furniture making, and in the garden, there is almost always a need for a saw. Labor productivity increases noticeably if the tool is motorized. You can’t do without it, just like you can’t do without the equipment for it - a saw blade. The speed and quality of part processing, as well as the amount of losses due to defects and waste, depend on how well the choice is made. The risk of injury should not be discounted - with an unsuitable “circle” it increases significantly.

By various reasons Amateur craftsmen and even some professionals neglect to purchase additional equipment and try to make do with one single (standard) disk. The main reason for this “ignorance” is obvious: a good saw blade costs about 70-100 not so conventional units... However, if we're talking about about a more or less significant amount of work and if burning out the saw motor is not part of your plans, it is better to approach the issue “in an adult way.”

Sellers-"consultants" in the markets are rarely able to give competent advice on this issue. The accompanying documentation in most cases is just brief information about the characteristics printed on the product and on the packaging. But in a serious authorized store you will be offered a catalog, sometimes quite detailed, with a description of the product. It will help you understand the issue, understand how the saw works and how it affects design features on the cutting process and result.

MAIN CHARACTERISTICS
There are two types of construction: monolithic (the material is the same everywhere) and carbide wheels. At the tips of the teeth of the latter there are plates made of hard alloy (usually tungsten or cobalt carbide). Both have their advantages and disadvantages.

Monolithic discs become dull quite quickly and require periodic sharpening and setting of teeth. But such a disk is repairable and can withstand several sharpenings, which are easy to do yourself. Such blades often have a large number of teeth and are designed for wood.

Discs with carbide teeth (they are usually designated by the letters HW) are noticeably more expensive, but they last longer before regrinding, but sharpening them without a special machine is extremely difficult. Nevertheless, it is this equipment that has gained the greatest popularity. The reason, first of all, is that such discs manage to justify themselves, even if they are not sharpened at all, but simply replaced with new ones. An additional and often very important “plus” is the quality of sawing the material. In addition, carbide tips are necessary when sawing laminate and metals.

The main dimensions of circular saws are usually indicated on the blade itself. The outer diameter of the disk does not affect the speed and quality of work, but it directly affects maximum depth cutting Naturally, the size of the blade must be proportional to the drive power. The bore diameter is related to the outer diameter; There are several standard values ​​for this parameter, the most common of which is 30 mm.

PECULIARITIES
When buying a disc, it is very important to consider not only WHAT is to be cut, but also HOW this will happen, because an incorrectly selected disc will not work well and will quickly become unusable. Even the worst case scenario is possible - failure of the saw motor due to overload.

When cutting material, overheating is extremely undesirable. The discs “burn” from strong friction against the walls of the cut. The saw is cut, that is, it deviates from the straight cut. Local overheating causes “swelling” to appear, which due to thermal expansion becomes larger and rubs even harder. Burns appear; due to uneven heating, the saw bends with the propeller. The process develops like an avalanche. To prevent the disc from “stealing,” temperature compensators are often made on its body - slots 1-2 mm wide and 15-20 mm long with round holes at the end, located radially from the interdental cavity. Some blades have holes filled with copper rivets to reduce vibration and improve cooling of the saw. In addition, the intricate configuration of the slots often has other functional purposes - vibration damping, noise reduction, cooling, etc. Some discs (for example, those from Freud) have a groove in the shape of a circle, obtained by rolling. It compensates for radial stresses that arise when the blade rotates at high frequency.

Laser cutting of saw bodies, the use of radial grooves, additional processing and coating of the saw body, for example, with Teflon, etc., help to increase the service life and expand the capabilities of the saw. and so on.

Important parameter high precision for a circular saw - no deviation of the disk from the cutting plane, its end and radial runout is minimized. The cleanliness of processing, productivity, and working life of the tool depend on this. For experienced craftsman A disc with an end runout tolerance of 0.15 mm is optimal. There are discs that are more careful; these are expensive imported models with a tolerance of 0.05 mm. The use of such equipment on household-grade machines is not justified.

WHAT TO BUY?
When choosing a disc for a specific operation, you need to pay attention to the angle of inclination of the teeth, sharpening geometry, expansion slots, protrusions following the tooth, and recesses between the teeth.

It must be remembered that high-quality cutting with a circular saw with a trimming disc installed on it is impossible, and vice versa. The reason for the incompatibility is that the trajectory of the tooling in the workpiece is different. Thus, disks for pendulum saws must have a negative angle of inclination, then the cutting part of the teeth is used more efficiently with the least load on the engine, and the efficiency is much higher than when using a disk with a positive inclination angle. If the “positive disk” moves along the trajectory of the pendulum, the teeth will work backwards, the load on the engine will increase, performance will decrease, and overheating will occur.

At the same time, if circular saw or manual circular saw install a “negative” disk, and even with a frequent arrangement of teeth, the cut will “repel” the workpiece, the sawdust will clog into small recesses, which will cause an overload of the saw motor - the longitudinal cut will be made with great difficulty.

To follow everything stated “in kind”, it is enough to carefully look at how the equipment works at the moment the tool is turned off. The preferred situation is when the saw teeth are directed at an angle to the material and cut it off like a plane knife, rather than cutting down a thin branch like an ax. In the latter scenario, chips at the tooth exit are guaranteed.

As shown above, saw blades can be divided into several types according to the type of work. Universal canvases are very rare. An example is the canvases of the “T” series from kwb, but even those are not fully universal, since they are suitable exclusively for miter saws. Unfortunately, there are no ones that not only cope equally well with all tasks, but are also suitable for all known types of tools. We also have to put up with the fact that one disk is not capable of providing both quality and performance at the same time.

To summarize the description of the characteristics, we will clarify which drives are suitable for various materials.

If you cut laminated material with saws with an “oblique” sharpening (with alternating angles), the main load falls on the top of the triangular angle, which leads to its rather rapid dulling. And on cutters with a “trapezoid” there are no sharp corners, so the durability of such saws is higher. The optimal number of teeth is average (48-60 for blades with a diameter of 200-300 mm).

Of course, when sawing double-sided laminate, even such discs are not able to completely eliminate the appearance of chips, however correct selection equipment can significantly reduce the size and number of defects.

For cutting non-ferrous metals, discs are produced with a large number (from 64) of cutters having a negative or positive angle of inclination. The former are used when sawing thin-walled profiles, thereby reducing burrs on the tooth exit side. The thick-walled profile is cut second. To increase resistance to lateral loads, saws for metal are made thicker, which is why they differ from saws for laminate.

To work with wood, a disk is selected based on the following rules:

It is better to make a longitudinal cut with a disk with fewer teeth, a positive angle of inclination and large depressions between them (they are needed for effective removal sawdust). For a disk with a diameter of 230-250 mm, the recommended number of teeth should be in the range of 18-24;

For transverse finishing cuts, a disk with a large (up to 48) number of teeth is preferable.

It will help you make the right choice helpful information from the disc packaging. It shows in the form of pictograms the materials the disk is intended to work with, an arrow indicates the direction of the cut (crosswise or lengthwise), and the maximum permissible speeds and often the angles of inclination of the teeth are always given. Here are examples of such designations: “5 neg” (negative by 5 degrees) or “10 pos” (positive by 10 degrees). For clarity, the purpose of the saw (longitudinal or transverse cut) is illustrated with the image of a crosscut or circular saw.

To roughly assess the quality of the saw blade, you need to carefully examine its body. Dull teeth can still be corrected by sharpening, but a bad body is a death sentence. Look at the direction of the disc grinding in the light. A “normal” saw has marks from grinding tool diverge in circles from the mounting hole, the “budget” one will not have such traces. This means that in the first case the saw was ground separately, that is, calibrated after cutting from the sheet. In the second case, the entire sheet was sanded (if it was done at all). Obviously, the balancing and uniform distribution of internal stresses that arise during operation will be more durable in the first case. Pay attention to how the surface of the disc is polished. If there are roughnesses and rough processing, then it is not difficult to imagine how the resin will stick to them. And a dirty tool will not give the desired result.

Even on a good saw, the inscriptions are made with a laser, and not with paint, which will quickly wear off. The inscriptions on the disk will help with its further maintenance.

TECHNICAL DETAILS
The first feature that the buyer pays attention to is the number of teeth. This characteristic quite clearly defines the purpose of the disk. According to this criterion, carbide equipment is divided into three categories.

Small number of teeth suitable for wood various densities and rough cutting particle boards. In dense wood, especially across the grain, the cut surface will be of poor quality. Medium-tipped blades have a wide range of applications - from high-quality rip and cross cuts of solid wood to rough machining of soft metals. Discs with a large number cutters are not advisable to use for soft wood, but in other cases (cross cuts in dense solid wood, sawing boards, plastics, laminates and metals) they provide maximum quality. True, they require increased drive power.

Another factor influencing the quality and speed of cutting with a carbide-tipped disc is the geometry of their sharpening. Today, the most widely used forms of sharpening are: flat tooth sharpening, alternating sharpening inclination and trapezium - straight tooth. The tooth angle can be negative or positive. Let us explain - we are talking about the angle formed by the front cutting edge of the tooth and the radius line (Fig. 1). It affects the cleanliness and efficiency of cutting various materials (more on this below).

Flat (straight) sharpening (Fig. 2) has equipment designed for carpentry and other rough work that requires quick cuts in solid wood, when quality does not matter.

Alternating inclination of sharpening is the most universal, applicable for longitudinal and transverse cuts of all types of wood and wood-fiber materials, plastics, laminated materials, plywood (Fig. 3). The negative “angle of attack” of variable teeth is good for finishing cuts in solid wood, cutting panels (including chipboard), non-ferrous metals and plastics.

Trapezoidal sharpening (Fig. 4) is ideal for working on chipboard, plastic and non-ferrous metals, as it prevents splitting of the laminated material. The trapezoidal tooth performs rough cutting, and the following flat tooth ensures clean cutting edges. This shape, combined with a negative inclination angle, is ideal for thin-walled metal and plastic profiles, for high-quality cutting of slabs, panels and laminates.

Less common is the alternation of oblique and straight-sharpened tips. Such saws can withstand heavy loads and are designed for rough construction wood, particle boards, aerated concrete, as well as boards with nails and concrete residues.

Some models have teeth sharpened like a skate and have a concave front surface (example: Metabo). They produce very clean cuts in veneered or veneered chipboards.

There are also saw blades on sale with feed limiters in the form of protrusions behind each saw tooth, which do not allow the workpiece feed speed to be excessively increased (Fig. 5). In addition, the limiter prevents damage cutting edges falling knots.

For all-metal (monolithic) discs, everything is much simpler: straight sharpening and two types of tooth profile - sharp (like a hacksaw) and with a “back”, curved (Fig. 6). The first is suitable for finishing longitudinal and transverse cuts in soft and hard wood, the second is for fast sawing of soft wood in both directions.

The thickness of the canvas also matters. Thin saws have two advantages: they require less energy, and there is little loss of material to sawdust. But they are not as stable in operation and require more “gentle” handling, so for severe operating conditions you should choose thicker saws.

CONCLUSION
A wide selection of brands (manufacturers) can confuse the buyer. Indeed, how to choose suitable brand goods? It is easy to notice that the vast majority of equipment is Latin names. The explanation is trivial - in Russia there is still no competitive production of hard alloys; almost all goods are produced either in Europe or in China.

Almost every manufacturer has discs for all major types of materials. The differences are in the quality of products, the amount of know-how and, of course, in price. Another feature of a serious supplier is the breadth of assortment and simple, convenient classification. As is usually the case in the market, all the advantages and disadvantages are balanced. Cheap equipment cuts worse and wears out faster.

High quality and reliable drive It cuts more accurately, lasts longer, but also costs a lot. So choosing a specific brand is to a certain extent a matter of taste. Or expediency.

And finally, a couple of operating tips.

The disk, no matter how much we want it, is subject to lateral loads, so its task is to maintain lateral stability, and the user’s goal is to try to protect the equipment from such overloads. In addition, it is necessary to sharpen saws in a timely manner, since a very dull tool heats up more intensely and, therefore, becomes deformed. For this operation, specialized sharpening machines are produced.

When cutting material, it is necessary to reduce the amount of saw teeth extending above the workpiece, which beginner tinkerers often do not do. This improves cut quality, reduces heat, reduces cutting resistance and reduces engine load. The recommended protrusion of the saw teeth above the material being cut should not exceed 10-20 mm. If the machine design has the ability to adjust the height of the disk, follow this rule.