These are the passport characteristics specified in the operating instructions for the machine, then the pitch of the teeth must be carefully selected depending on the size and shape of the workpieces being cut. Right choice The pitch of the teeth ensures long service life of the saw: it provides the proper tooth pressure and sufficient dimensions of the cavity between the teeth to remove chips.

Band saws for metal are produced with constant or variable pitch. Pitch, or TPI, is English abbreviation from Tooth Per Inch, indicating the number of teeth per inch equal to 25.4 mm. Variable pitch is more preferable when cutting metal, as it has a much larger operating range compared to a constant pitch, which reduces the noise and vibration that occurs during sawing.

There are certain rules identified experimentally:

• There must be at least 3 teeth along the length of the cut. If less, the tooth may sink and break.
• There can be a maximum of 24 teeth per cutting length. If the number of teeth exceeds the maximum value, the cavity between the teeth does not accommodate chips, the saw overheats, and the service life is significantly reduced.
• The optimal number of teeth per cutting length is from 6 to 12.

To facilitate the selection of tooth pitch, special tables are used

• Select the table according to the workpiece shape
• Select the tooth pitch, taking into account the size of the workpiece being cut

Table 1. Solid blanks

Batch cutting

For cutting solid workpieces

Tab. 2 Profiles and pipes

Choose maximum size part to be cut. Then select the wall thickness. The intersection of these two parameters in the table shows the recommended tooth pitch. For faster cutting, you can use the next larger increment. It is not recommended to use a finer pitch, since overfilling the cavities between the teeth with chips leads to failure of the saw.

You have been given the task of finding tape cloth for a band saw machine for your production, but do you know what it is?

Then you've come to the right place! In this article we will look at the main nuances of selecting tape fabrics.

What is it? The tape blade is a tape welded to a ring (circle) with an N number of cutting teeth located on one side of the ring.

The tape - the basis of the canvas - is made of elastic spring steel. A profile strip made of high-speed steel (HSS) is welded to the tape, after which the required profile of the saw teeth is milled. The result is a strip fabric welded from two metals called Bimetallic.

The typical designation (marking) of saws is as follows:
M42 20x0.9x2362, 8/12TPI

• M42- Saw tooth material(it can also be M51, PQ, TSX...)
  M42 (analogous to 10Р2М10К8). An indispensable feature of this material is the excellent wear resistance of the cutting edges of the saw blade teeth. The main factor here is the size of the carbide particles and their uniform distribution in the structure of the material.
  The hardness of the cutting edges of the teeth is 67–68 HRC.
  This material is used for sawing the main grades of steel with a hardness of up to 45 HRC.
  M51(analogue 12Р10М4К10). A significant tungsten content in the tooth material increases the amount of carbides, which increases resistance to abrasive wear, and a high cobalt content increases the durability of the cutting edge.
  The cutting edge hardness is 69 HRC.
  Such advantages allow this tool to be used for cutting heat-resistant, high-strength and stainless steels with a large cross-section with a hardness of up to 45 HRC.
  The overall durability and service life of such a blade is 10-20% higher than that of saws with M42 teeth.
• 20 - saw blade width, mm
• 0,9 - saw blade thickness, mm
• 2362 - saw circumference, mm
• 8/12 TPI - saw tooth pitch per inch

For the most effective use band saws for metal, you need to pay attention Special attention correct selection of saws depending on the task at hand.

One of the most important factors choice is correct selection geometry, pitch and saw tooth material.

Tooth pitch

Tooth pitch is the distance between the vertices of a pair of adjacent saw teeth. Their choice depends on the type of metal being processed and the speed at which the band saws feed. Too large a step will cause an increase in stress, as well as a deterioration in the quality of the cut. Small pitch ensures smooth surface, but requires high energy consumption.

Tooth height

The height of a tooth is the distance between its top and the base of the socket. The presence of an interdental recess allows you to remove sawdust generated during the sawing process from the working area. The volume of this recess should be sufficient, and sawdust should not occupy its entire space. Their excess will be squeezed out along the sides of the saw blade, increasing resistance and friction, which makes it necessary to apply more effort when sawing.

An incorrect choice of band saw tooth height can cause overheating of the blade and the appearance of a so-called “wave”. In addition, additional stresses may arise, which can trigger the appearance of microcracks.

Front corner of tooth

The front angle of a tooth is the angle between the perpendicular of the band blade and the front edge of the tooth itself. The sharpening angle allows the tooth to engage and cut the metal blade.

It should be taken into account that too big size angle will not allow you to cut metal accurately. A small sharpening angle produces a smoother surface on the metal, but if it is too small, there is a significant reduction in productivity.

Incorrect selection of the toe angle provokes dulling of the teeth and the appearance of cracks in their cavities. The optimal sharpening angle is determined depending on the metal being processed.

What material are you going to cut?

Determining the saw pitch

The number of teeth per inch is determined depending on the material and type of workpiece. If we are sawing thin-walled pipes, sheet metal, profiles, then it is necessary to use a blade with the smallest tooth pitch, which corresponds to more teeth per 1 inch of saw. If you use a large step, this can lead to rapid destruction of the cutting part of the tooth.

To cut large solid workpieces, you should choose a saw with the largest pitch. Fewer teeth per inch create deep grooves and prevent chips from getting stuck, increasing productivity.

Attention!

During the cutting process, there must be at least 3 teeth in the metal at the same time; a smaller number can lead to blade breakage.

When manufacturing blanks, one of the main operations is the division of a round (or other) rolled bar (rod) into separate blanks. For this, various technological processes can be used: dividing the workpieces on press shears, cutting with friction discs, saws, abrasive wheels, etc. As an example, two options are considered for cutting rolled products into workpieces with circular saws made from various tool materials, since this method relates to for cutting processing (Fig. 3.26).

Rice. 3.26. Scheme of cutting rolled steel with a circular saw.

To cut the workpiece, circular saws are used, which are made either from high-speed steel R6M5 or from hard alloy T5K10. When cutting a workpiece, the tooth circular saw simultaneously participates in two movements: rotational cutting movement at speed v (Fig. 3.27) and feed movement S M , which is selected according to the rational thickness of the cut layer A.

Rice. 3.27. Kinematics of cutting with a circular saw.

When cutting with an edge with two tips, unfavorable (box-shaped) chips are formed, which reduces the wear resistance of the saw and prevents an increase in the thickness of the cut layer.

A more favorable cutting scheme is one in which only one tip of each tooth is involved in the work. To do this, make a “spread” of the teeth at an angle of inclination of the cutting edge (Fig. 3.28).

Rice. 3. 28. Geometric parameters of circular saw teeth.

In addition, part of the edge near the non-functioning vertex is cut off. To increase the durability of the circular saw near the working top of the tooth, it is advisable to round the top of the saw teeth with a radius of 0.5... 1.0 mm or sharpen the transition edge at an angle of 5º. Maximum permissible cut thickness A are selected based on the permissible load on the tooth, which in this case will be 0.1 mm. Since the part is stationary and the feed is carried out in the direction of the thickness of the layer being cut, the feed per tooth S z equal to the thickness of the cut layer A:

S z = a = 0.1 mm.

The depth of cut is determined by the cutting angle and the length of the cutting edge involved in cutting. To create small positive minor leading angles by rotating the cutting insert, the leading leading angle φ can be set to just under 90° (e.g. 85...87°).

To avoid three-sided cutting, which produces hard box-shaped chips, the teeth are “set apart” or the tooth width is slightly reduced to exclude one of the vertices from the cutting process (left or right - alternately for each subsequent tooth). Thus, on each tooth the cutting depth and chip width are slightly less than the width of the circular saw (cutter). Feed per revolution of a cutter (saw) with 32 teeth: S Q = S z z = 3.2 mm.

The number of teeth simultaneously involved in the work depends on the angle of contact of the saw with the workpiece and on the angle between the teeth. The contact angle of the saw with the workpiece depends on the ratio of the diameters of the workpiece D 3 and the saw D fr (Fig. 3.29): Θ М = 2aicsin D 3 / D fr= 49.2°

Rice. 3.29. Determining the contact angle of the saw with the workpiece.

The number of teeth on a circular saw is determined for design reasons, but taking into account the resulting cutting forces. With a large number of simultaneously working teeth, cutting forces, torque and cutting power increase, especially as the teeth wear. Since the diameter of the cutter is much larger than its width, an increase in forces and torque is undesirable. However, an excessive reduction in the number of teeth is also undesirable, since this can lead to a decrease in processing productivity and an increase in the unevenness of the cutting (milling) process.

Thus, when assigning the number of teeth on a circular saw, it is necessary to take into account the number of teeth simultaneously involved in the work, and the resulting forces that push the circular saw away from the workpiece.

In some more advanced cutting machine designs, the minute feed is controlled directly by the feed mechanism. In simpler machines, feed and rational cut thickness per tooth are ensured by adjusting the vertical force P v , the required value of which is supported by the hydraulic system of the machine. The actual force required to ensure the required thickness of the cut layer varies depending on the width of the tooth wear chamfer and the number of teeth actually simultaneously in contact with the bar being cut (Fig. 3.30).

Rice. 3.30. Dependence of the feed force P v on the number of teeth z simultaneously in contact with the workpiece being cut, for a sharpened ( h h= 0.1mm) and blunt ( h h= 1mm) circular saw blades: 1- h h= 0.1mm; 2 - h h= 1mm.

Thus, as the saw approaches the middle of the workpiece, as the saw wears out, the worker must increase the pressure in the hydraulic system, thereby increasing the feed force and ensuring an approximately constant, optimal thickness of the cut layer.

We will select the permissible cutting speed based on the highest temperature back surface on a worn tooth (h 3 = 1 mm, fig. 3.31). In the first case, for a saw made of high-speed steel, Q 3 = 500 ° C, in the second case, for a saw with carbide teeth, Q 3 = 700 ° C. Reducing the cutting temperature has a beneficial effect not only on increasing durability, but also on the forces arising during cutting.

At a temperature of 400 °C, a stable build-up takes place on the front surface of the tooth, which facilitates the cutting process and reduces the level of vibrations: In this sense, the use of a high-speed steel saw for cutting a bar is preferable to the use of a saw with carbide soldered teeth, which, when cutting the workpiece, are more At high temperatures there is practically no growth. The feasibility of using a carbide saw arises if a significant increase in the productivity of cutting rods into workpieces is required. The dependence of the temperature on the front surface of the tooth on the cutting speed is calculated using the program.

Rice. 3.31. The influence of cutting speed on the maximum temperature of the rear surface of the cutting blade of a disk cutter (diameter 600 mm, number of teeth z = 32) when cutting a bar of steel 45 with a diameter d = 250 mm: 1- rational temperature for a hard alloy; 2 - rational temperature for high-speed steel;

3 - with h h = 1 mm; 4 - h h = 0.2 mm

When cutting a bar with a diameter of 250 mm from steel 45, the cutting speeds for these types of saws are respectively 25 and 65 m/min, and the rotation speed of the circular saw n is equal to 11 and 40 min -1, respectively. Minute feed S M = S 0 n= 21 and 64 mm/min respectively. For speeds of 21 and 64 m/min, the approximate cutting power will be 6 kW for the HSS saw and 16 kW for the carbide saw, respectively. The geometric parameters of the circular saw are given in table. 3.3.

We are pleased to introduce the latest range of industrial bandsaw blades from the companyBahco. Continuous development and investment in research and development have resulted in the creation of innovative and high quality products for both multi-purpose and industrial cutting. Bahco offers a variety of patented products, from the unique 3857 Easy Cut, designed to cut different sizes and types of materials with the same blade, to modern high-performance carbide blades with set and non-set teeth for cutting a variety of materials used in the new generation of civil engineering. and military aviation, complex energy projects and high-tech industries.

general information

Wiring types

Setting is the slope or angle given to the teeth of a saw blade to provide clearance between the body of the blade and the edges of the teeth. Below are Various types wiring:

Zagrebnaya

With a rake set, one tooth is set to the left, one tooth is set to the right, and one tooth (ridge) is left without set. This type of layout is used on canvases with a constant pitch, for example, regular or hook. It is also used for contour and friction cut blades on vertical band saws.

Combined wiring

With a combined set, used in combined blades, a combed (without set) tooth is followed by teeth in the sequence left, right, left, right. This pattern is repeated in each group of teeth, starting and ending with the most big tooth in Group.

Teeth per inch (TPI)

The number of teeth per inch (TPI) determines the blade pitch and can vary from less than 1 to 24. Thin-walled workpieces such as pipes, tubes, sheets, etc. require saws with a fine tooth pitch, otherwise there is a risk of damage or tooth decay. Large cross-sections should be cut with a coarse pitch saw, that is, fewer teeth per inch. How fewer teeth involved in the workpiece, the higher the cutting ability. The fact is that the penetrating power of each individual tooth is higher if the saw feed pressure is distributed over a smaller number of teeth. The coarse pitch (small TPI) thus increases productivity and provides the desired large chip flute. Soft materials such as aluminum and bronze require a larger flute. The coarse pitch prevents the formation and accumulation of chips in the recesses between the saw teeth, which can impair cutting and damage the blade.

Band saw cutting

Machine
Check repeatedly:
. Operation of the chip cleaning brush
. Wear and adjustment of guides
. Web tension with a tensometer
. Blade speed with tachometer
. Concentration of cutting fluid using a refractometer

Cutting fluid/Emulsion
coolant lubricates, cools and carries chips away from the cut. Important:
. Use good coolant
. Use recommended coolant concentration
. Ensure that the coolant reaches the cut at low pressure and high flow
Workpiece
. Ensure that the workpiece is firmly fixed so that there can be no vibration or rotation
. Do not use bent or damaged workpieces

Run-in
To achieve maximum blade life, always use the recommended blade speed, but reduce the feed speed to 1/3-1/2 for the first 10 minutes of cutting. Over the next 10 minutes, increase the feed speed in stages until you reach the recommended feed rate.

Teeth guard
Keep the tooth guard on the blade until it is installed on the machine to prevent premature chipping of the tooth heads.

Feed rate/chips

It is important that each tooth of the hacksaw blade cuts chips of the required thickness. This is determined by the choice of tooth pitch, speed of movement band saw and feed speed. Start by selecting the correct tooth pitch, then set the blade speed. You can now set the correct feed rate by examining the chips your band saw blade produces when cutting. Refer to the illustrations below and adjust the feed speed or blade speed accordingly.
In order to obtain additional information For cutting data, contact your local Bahco representative who can help you find the correct cutting data for your specific application.
1. Thin or fine chips - increase feed speed or reduce blade speed
2. Loose chips - correct cutting data
3. Thick, heavy or blue chips are too high speed, reduce the feed speed or increase the blade speed
1. 2. 3.

Choosing a saw tooth pitch when sawing massive workpieces

This diagram will help you select the correct tooth pitch for cutting massive parts. AndThe ideal choice is at the widest point of each field.
Example 1: When cutting Ø 150 mm (6 in) bar, use 2 TPI if you select a uniform pitch blade. Use 2/3 TPI or 1 4/2 TPI if you choose a variable pitch blade.
Example 2: If you are sawing soft materials such as plastic, aluminum or wood, select a pitch two pitches larger than recommended. When cutting aluminum parts 13-20 m thick m (1/2-3/4 inch size) use a blade with 6 TPI or 5/8 TPI.

Selecting the saw tooth pitch when cutting pipes and profiles

This diagram will help you find the correct tooth pitch for cutting pipes and profiles. The recommended tooth pitch for cutting profiles is in the field where the width corresponds to the wall thickness of the profile.
Example 3: When cutting 100 x 10 mm (4 in x 0.4 in) channel profile, select a 5/8 TPI or 4/6 TPI blade. The recommended tooth pitch for cutting profiles is in the field where the outer diameter corresponds to the wall thickness of the pipe to be cut.
Example 4: When cutting 40 x 1.6 mm (1.5 in x 0.06 in) pipe, select a 10/14 TPI blade.

A hand saw, at first glance, is a fairly simple tool that does not require much maintenance. However, few people know about the criteria for choosing a saw and its types. Like other tools, a hand saw has certain signs of quality and characteristics.

Basic parameters of hand tools for cutting wood

The hacksaw is one of the most necessary tools in every man's inventory. This device allows you to easily change the dimensions of wood and plastic lumber. Using a hacksaw, you can perform a lot of operations in construction, cut branches in the garden, shorten fence poles, and so on.

A hand saw is used to work with lumber

But when purchasing such a seemingly simple tool, not everyone thinks about how to make the right choice and what criteria need to be taken into account. A hacksaw has its own special parameters that can affect the quality of work. There are four basic parameters when choosing a hacksaw: blade length, tooth size, steel type and handle type.

Blade length

For ease of use, the length of the hacksaw blade is chosen so that it is twice the size of the material at the cut site. This allows you to effectively remove sawdust during work due to the fact that all the teeth of the blade will come out of the board/log. In addition, this ratio of the size of the hacksaw and lumber contributes to a greater range of hand movement. This, in turn, takes much less effort. In construction, a universal hacksaw with a blade length of 45–50 centimeters is most often used. To work with small bars and boards, a blade 30–35 centimeters long will be sufficient.

Tooth size

This is perhaps the most important parameter. After all, the speed and accuracy of cutting depends on the size of the tooth.. The number of teeth per inch of blade is usually denoted by the TPI coefficient. To work more accurately with the material, it is necessary to use a hacksaw with a high TPI coefficient, that is, with big amount teeth. When choosing a blade with a TPI of at least 7–9, and a distance between teeth of no more than 2–4 mm, the surface at the cutting site will be smoother and without torn edges. For working with large beams and garden trees, a blade with a TPI of 3–6 and a tooth spacing of over 4 mm will work well. Using such a hacksaw will reduce the effort required and increase the speed of cutting the working material.

Tooth pitch correspondence table

Sharpening teeth

The usual triangular shape of hacksaw teeth is taken as standard. The teeth are made in the form of an acute triangle or isosceles, depending on the purpose of the cut. Such a blade can be sharpened with particular ease by repeating all the angles of the teeth. This blade can be used for both longitudinal and transverse cuts to avoid rough notches.

The teeth of a classic hacksaw are made in the shape of a triangle and can be sharpened

Video: self-sharpening hacksaw teeth for wood

But modern hacksaws, unlike classic ones, have hardened teeth with a non-standard trapezoidal shape. Such saws are endowed with increased strength and are resistant to wear. Their steel cannot be sharpened, and it is very difficult to maintain all the angles of the sharpened teeth.

Modern hacksaws are made with hardened teeth in the shape of a trapezoid.

Steel type

High-grade stainless steel is most often used to produce hacksaw blades. Typically, wood saws are made of steel with a hardness of HRC45. Very often, manufacturers combine steel in the canvas. In a hacksaw with a combined blade most of also made of 45 steel, but cutting part made of steel 55 and 60. When the cutting edge is hardened, wear resistance increases. This type of tool can be easily distinguished from a regular hacksaw by its dark, hardened teeth.

The first forged saws were made back in Ancient Greece. Forging gave high hardness to the metal and improved the quality of the tool.

Handle type

The ease of use of the saw depends on the correct choice of saw handle. Handles are made of wood or plastic. Very important point- the surface at the grip site should be such that the hand does not slip. This can be eliminated by scarring the handle or covering it with a rubber layer. The hacksaw can be either a classic cast saw or with a reversible blade. The latter allows you to replace the canvas, which is very convenient.

How to choose a hand saw

By combining all the basic parameters of the saw, everyone can easily decide for themselves which one suits them best. When choosing a tool, you need to decide for yourself which saw is more suitable - a carpenter's or a carpenter's saw. If the most important thing is cutting speed, then, of course, you need to purchase a carpenter's tool. A carpenter's hacksaw has fewer teeth per inch, which helps fast performance and removal of sawdust. If cutting accuracy is a priority, then you should use a carpentry shop.

The quality of a hacksaw can be determined in simple ways. First you need to visually verify the evenness of the canvas. Then you need to bend the canvas with a little effort and release it as soon as resistance appears. After the blade plays back and calms down, you should again check the evenness of the blade. If it is slightly deviated from the original position, then the tool is of poor quality and it is not recommended to buy it.

If you need a rip saw, you need to choose a hacksaw with sharp teeth. The teeth of such saws are sharpened only on one side, so the cut will be made only in one direction - away from you.

Blade teeth for rip sawing sharpened in the shape of an acute triangle

When longitudinal sawing, the cut occurs parallel to the fibers of the material. For rip sawing, circular saws and bow saws are well suited.

Crosscut saws are the most common. Their teeth are shaped like isosceles triangle and sharpened on both sides. This allows you to cut in both directions.

For cross cutting, the teeth of the blade are made in the shape of an isosceles triangle and sharpened on both sides

At cross sawing The material is cut across the grain. For such sawing, classic hacksaws, hacksaws with a backrest, and, for large material thicknesses, two-handed saws are suitable.

The price of the saw is also an equally important factor when choosing. A more expensive hacksaw guarantees reliability and wear resistance. Those saws whose price is significantly lower than average are made from cheaper raw materials and do not guarantee you long-term service.

What types of hand saws are used for what purposes?

1. The classic hacksaw is the most common of all. It has a long and wide canvas. If the blade is too long, the hacksaw may tilt to the side when cutting. Great care must be taken to avoid deviation of the cutting line from the initial marking. This hacksaw is suitable for working with timber, boards, chipboard and so on.
2. Hacksaw with back. This saw model has a rigid rib attachment, which minimizes the vibration frequency of the blade. And also such a hacksaw has more fine teeth and a higher TPI ratio. They are designed for cutting plywood, chipboard with a coating layer and sawing profile strips.
3. Finish saws have an adjustable handle. They are needed for cutting grooves, grooves and straight and profile planks.
4. A circular hacksaw, or a hacksaw with a narrow blade. It is also used for cutting grooves, as well as for cutting out parts with rounded areas and large holes.
5. A bow saw is well suited for cutting knots and rough parts of material, as well as for cutting out parts from plywood and wood. This hacksaw is distinguished by a thin blade fixed on both sides in a frame. It is worth noting that you need to work with it extremely carefully due to its increased fragility.
6. The award has two handles. The appearance of such a saw is in many ways similar to a plane. It is used for cutting tenons and grooves, deepening holes and slots in materials of any hardness.
7. Garden saw with curved blade. Most often, for greater convenience, they are made folding. This saw is well suited for garden work. The saw blade is made of chrome steel. Widely spaced teeth with an inclination in the direction of the handle will allow you to conveniently cut down twigs and branches, placing emphasis on yourself while cutting.
8. A two-handed saw has the highest productivity. It has two wooden handles. For greater efficiency, cutting with such a saw requires two people. A two-handed saw is often used for sawing large logs and trees.
9. A hand or pocket chain saw is a small piece of chain with two handles at the ends. This saw is convenient for both one and two people to work with. The log or branch is wrapped around a chain and cut is made using the handles. A manual chainsaw, like a folding one, is well suited for gardening.

Photo gallery: types of hand saws

This classic hacksaw can be easily sharpened. This hacksaw has hardened teeth and increased wear resistance. A hacksaw with a back or butt minimizes vibrations of the blade during work. A hacksaw with a narrow blade is well suited for cutting holes and grooves.
This type of saw has an adjustable handle, which allows you to work at the desired angle. A bow saw is well suited for cutting parts from plywood. This type of hacksaw is similar to a plane and is used for cutting tenons and slots. A two-handed saw is suitable for cutting large logs.
Garden saws with curved blades are well suited for cutting down knots and small tree branches.
The hand chain saw is compact and well suited for sawing logs while camping and branches in the garden.

Thus, having carefully studied all the nuances regarding hand saws, everyone can choose the most suitable option for themselves. Choosing the right tool will provide you with high-quality and enjoyable work.