Sequence of actions when choosing band saws

1. Machine model.

Depends on the machine model:

Band saw loop length. For example, length, width and thickness strip fabric respectively 5500 x 34 x 1.1 mm. The nominal length of the saw, which is indicated in the machine passport (in this case 5500 mm), may have a tolerance of +/- 50 mm. This is the stroke of the tension pulley.

Width and thickness of the canvas. This is usually a constant value. These dimensions have long been formed from the standard sizes of produced “Birmingham rolled” steel and have the following series: 10x0.9; 13x0.9; 20x0.9; 27x0.9; 34x1.1; 41x1.3; 54x1.6 and so on.

2. Cutting edge type of bimetal band saws.

Currently the most widespread have band saw blades with the following cutting edge types:

Selection of band saws depending on the hardness of the teeth:
- hardness of the cutting edge of carbon band saws: 62-64 HRC;
- hardness of the cutting edge of bimetallic band saws M2 (Matrix): 62-64 HRCе;
- hardness of the cutting edge of bimetallic band saws M42: 67-68.5 HRCе;
- hardness of the cutting edge of bimetallic band saws M51: 67.5-69 HRCе.

The price/durability ratio is most preferable for saws with a cutting edge made of M42 high-speed steel.

The average price of one meter of WIKUS 34x1.1 saws from M42 is ~9-11 euros, the average price of one meter of Matrix 2 is ~7-8 euros, the average price of one meter of M51 is 12-14 euros.

The ratio of saw durability when cutting structural carbon steels: M42 - 100%, Matrix 2 ~ 60-70%, M51 ~ 115%.

The use of Matrix 2 band saws is justified when sawing small volumes of workpieces, when cutting non-ferrous metals and profile workpieces.

Band saws M51/M71 are used for cutting difficult-to-cut heat-resistant and stainless steels and alloys, titanium, etc.

3. Rake angle of the cutting edge of the teeth.

Band saws are available with teeth with a rake angle of 0°, 6-7°, 9-10°, 14-15°.

The larger the rake angle, the better the cutting ability of the teeth, but the less wear resistance.

Saws with a rake angle of 0° and 6-7° are produced for cutting profile workpieces.

Saws with a rake angle of 10°-15° are used for cutting workpieces with diameters over 120 mm, viscous materials, non-ferrous metals, plastics, etc.

4. Selecting the tooth pitch.

TPI- English abbreviation from Tooth Per Inch (teeth per inch - number of teeth at a distance of 25.4 mm). The German abbreviation for TPI is ZpZ.

Constant pitch saws. All saw teeth have the same pitch and shape. Used for cutting solid workpieces, soft materials and non-metals.

Saws with variable pitch. Periodically changing tooth root profile. Provides some reduction in vibration and noise during cutting. Used to expand the range of workpiece sizes.

The pitch of the teeth depends on the width of the workpiece being cut.

The rule usually applied is at least 3 teeth in the body of the workpiece, optimally 10-12 teeth, maximum 22 teeth.

For example, to cut an F100 workpiece, you can select a tooth pitch of 3TPI, 4TPI, 3/4TPI, 4/6TPI.

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

Selecting the pitch of band saws for profiles and pipes
	Diameter
Wall thickness	<40	80	100	150	200	300	500
3	8/12	8/12	8/12	8/12	6/10	6/10	6/10
8	8/12	6/10	6/10	5/8	4/6	4/6	3/4
12	6/10	5/8	5/8	4/6	4/6	4/6	3/4
15	5/8	4/6	4/6	4/6	3/4	3/4	2/3
20		4/6	4/6	3/4	3/4	3/4	2/3
30		¾	3/4	3/4	2/3	2/3	2/3
50				3/4	2/3	2/3	1,33/2
100					2/3	1,33/2	0,75/1,25
120					1,33/2	0,75/1,25	0,75/1,25

If necessary, we will help you decide on the choice of band saws for a specific task.

Band saws for wood and metal are widely used in production and at home by home craftsmen. The main cutting tool of these units is a band saw, which wears out over time and requires sharpening or replacement with a new one. You should know that not only the quality of material processing, but also the performance of the unit as a whole depends on the correct choice of blade for a band saw machine.

The cutting blade for this type of saw is a strip with a certain number of teeth, welded in the form of a ring. The base of the tape is made of spring steel, which has high elasticity. A strip made of high-speed steel is welded to the base, on which the teeth are subsequently milled.

Every band saw for metal and more is marked. For example, the marking M42 20 x 0.9 x 2362, 8/12TPI is deciphered as follows:

• M42 – material from which the belt teeth are made;
• 20 – this value indicates the width of the canvas, mm;
• 0.9 – tooling thickness, mm;
• 2362 – saw blade circumference, mm;
• 8/12TPI – tooth pitch on the saw blade, per inch.

Cutters can be made from other materials, for example, from M51, PQ, TSX and others. M42 is highly wear-resistant and has a cutter edge hardness of 67–68 HRC. Therefore, saws made from this material can be used for cutting steel with a hardness of no more than 45 HRC. Saws with cutters made of M51 material are more resistant to abrasive wear than those mentioned above. The hardness of the cutter edges of these saws is already 68 HRC, thanks to which this equipment can be used to cut stainless steels, as well as steels that are characterized by high strength and heat resistance. In addition, the M 51 saw material allows you to cut thick steel workpieces, that is, parts with a large cross-section.

When choosing a band saw, you should pay special attention not only to the material from which the cutters are made, but also to their pitch, as well as geometry.

This is the distance between the edges of two adjacent incisors.

Advice! The tooth pitch should be selected depending on the type of metal, as well as the cutting speed.

A large step puts more stress on the unit’s engine and produces poor cutting quality. A small pitch of the cutters leads to longer sawing, increases energy consumption, but gives clean cut with a smooth surface.

For cutting sheet material, pipes (thin-walled) and profiles, you should choose a blade that has a minimum pitch between the cutting elements (1 inch). But if you need to cut a large workpiece solid metal, it is required to install a blade with the largest cutter pitch. The fewer teeth (per inch) the tool has, the deeper the groove they will create. Thanks to this, the cut becomes less clogged with chips. Also, a large tooth pitch on the equipment increases the productivity of the unit.

Tooth height

The height of the cutter is the distance from the bottom point of the cavity between the teeth to the top of the cutting element. Due to the presence of a cavity chips are removed, formed when cutting metal. The height of the tooth should be sufficient so that the cavity does not become clogged with chips, and the sawing process occurs without difficulty. In addition, insufficient tooth height causes overheating of the blade, as a result of which microcracks may appear on it.

Front angle of tooth

The rake angle or sharpening angle is responsible for the degree of engagement of the blade with the workpiece material. A large sharpening angle will not allow you to achieve high precision when cutting metal. At the same time, a small angle allows for good cutting quality, but at the same time the productivity of the tool is reduced.

Choosing a blade for wood band saws

First of all, to choose the right band saw blade, you should look into instructions for your machine. It will indicate all the parameters of band saws that can be installed on this equipment model (maximum and minimum band width, as well as its length). The length of the blade must be exactly as indicated in the passport for the unit.

Tooling width

The width of the tape is selected based on the operations that will be performed on the machine. Also, the width of the belt is limited not only by the width of the pulley, but also by its diameter. If the diameter of the pulley is small, the wide belt installed on it will collapse and eventually break. Therefore, for each unit there is a limitation on the width of the equipment.

For straight cuts Usually saws with a width of 20 to 30 mm are used. Of course, using a circular saw you can make a longitudinal cut faster and more accurately. But there is a height limitation on it, which is no more than 80 mm. On band saw machines it is possible to process workpieces with a height of up to 200 mm or more.

But the main task of belt units is figured cut. The smallest accessory that can be installed on a band saw is a 3mm wide band. She cuts out a circle with the same radius.

The wider the tape, the larger the minimum radius that can be cut with it. For example, using a tape with a width of 12 mm, it will not be possible to cut a radius of less than 60 mm. And for a tape with a width of 25 mm, the minimum radius will be about 100 mm.

On average, the width of the blade should be three times smaller than the required cutting radius on the workpiece. Therefore, equipment is selected in accordance with the assigned tasks.

Tooth pitch

Indicated by a number indicating the number of cutters per inch. The numerical value of the step is set before the abbreviation TPI. When choosing a step you should consider:

• what is the thickness of the workpiece;
• what hardness the workpiece material has;
• what kind of cleanliness is required to obtain the edge of the part after cutting.

To effectively cut plastic and saw wood, the belt must have at least three cutters per inch. The more cutters there are per inch, the better the cut will be. But this will reduce the feed speed and reduce the maximum thickness of the workpiece.

Based on the pitch of the teeth, the blades are divided into two types: “skip” and “regular”. Type of canvas “skip” has a step from 3 to 6 TPI. There is space between the teeth for efficient removal of sawdust, since poor removal of them reduces the quality of the cut. Type of canvas “regular” has teeth shaped like a triangle. They are placed on equipment in increments of 10 TPI and higher. This type of teeth does not have enough space to quickly remove chips. Thanks to the larger number of cutting elements, the cut with such a blade turns out to be quite clean. The equipment can be used for sawing workpieces of small thickness and hard materials.

Advice! When sawing hard workpieces, it is necessary to reduce the feed.

These types of canvases have the following characteristics.

Incisor shape

Belt blades can have the following tooth profiles.

Teeth setting

The teeth on the saw are set apart in order to reduce friction of the blade on the workpiece and to prevent it from jamming. The width of the cut should exceed the thickness of the equipment by approximately 30-60%.

The placement of incisors can be of three types.

It is important to know that when setting the teeth, not the entire incisor is bent, but part of it: from 1/3 to 2/3 of the distance from the top of the tooth. Each tool manufacturer recommends its own value for tooth deflection to the side. But on average it is in the range from 0.3 to 0.7 mm.

The softer the material, the further the saw should be set, and vice versa. But you should not allow the cutters to be positioned in such a way that uncut areas remain in the center of the cut. You should try to keep the teeth deviated to the side at the same distance. If the setting is uneven, the band saw will move in the direction where the teeth have a stronger slope.

Band saw sharpening

Of course, it is better to sharpen a band saw on a special machine, in specialized workshops. And professional saw sharpening is inexpensive. But if for some reason you do not have the opportunity to take the saw for sharpening, then you can straighten the tool yourself.

Band saw sharpening is done using small file or needle file along the front and back edges of the incisor with several movements (3-4) for each tooth.

The band saw can also be sharpened using an engraver using equipment designed for sharpening chain saws.

The equipment is inserted into the engraver, and the cutters are sharpened using gentle movements along the top of the cutter.

There is no need to remove much metal, just lighten it.

Advice! When working with the tool, do not allow the cutter to slide off the top of the tooth towards the next one. This way you will shorten it, after which you will have to adjust all the teeth to its height.

You can also try sharpening and metal saws. But usually they are not sharpened, since the cutting part of these saw blades is either bimetallic or has a hardening zone. The teeth on such belts work until they crumble and may have microcracks. If you oversharpen them, they will begin to crumble faster or will cut even worse.

Saw tooth pitch for massive workpieces

This diagram will help you select the correct tooth pitch for cutting massive parts. The ideal choice is at the widest point of each field.
Example 1: When cutting a bar with a diameter of Ø 150 mm ( 6 inches) use 2 TPI if you choose a blade with a uniform pitch. 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, choose a pitch that is two steps larger than recommended.
When cutting aluminum parts with a thickness of 13-20 mm ( 1/2-3/4 inch) use a blade with 6 TPI or 5/8 TPI.

Cutting pipes and profiles

The diagram below 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 profile wall thickness.
Example 3:
When cutting a channel profile measuring 100 x 10 mm ( 4" x 0.4") select a blade with 5/8 TPI or 4/6 TPI. 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 a pipe measuring 40 x 1.6 mm ( 1.5" x 0.06") select a blade with 10/14 TPI.

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 using 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 saw tooth is simultaneously involved in two movements: a rotational cutting movement at a 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 of 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 of the flank 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 occurs 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 rod 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 a high-speed saw and 16 kW for a carbide saw, respectively. The geometric parameters of the circular saw are given in table. 3.3.

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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 the different types of 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 largest tooth in the 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. The 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 large 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, band saw speed and feed rate. 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.
For more information on 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 - speed too high, reduce feed speed or increase 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.