# How to choose pulleys for a circular saw

## Calculation of pulley diameters

how to calculate the correct pulley diameters so that the knife shaft of the woodworking machine will rotate at a speed of 30003500 revolutions per minute. The speed of the electric motor is 1410 rpm (the motor is three-phase, but will be included in a single-phase network (220 V) through a system of capacitors. V-belt.

The diameter of the pulley, depending on the speed of the shaft and the linear speed of the pulley, determined by the formula:

where D1. pulley diameter, mm; V. linear velocity of the pulley, m/s; n. shaft speed, r/min.

It is easy to calculate that for a pulley on the shaft of an electric motor with a rotational speed of 1400 rpm, the minimum diameter of the pulley (increasing gear) at a linear speed of the belt 10 m/s will be about 136 mm.

The diameter of the driven pulley is calculated using the following formula:

where D1 and D2. diameters of driving and driven pulleys, mm; ε. slip ratio of the belt, equal to 0,007 0,02; n1 and n2. speed of driving and driven shafts, rpm.

Since the value of the slip coefficient is very small, the slip correction can be disregarded, that is, the above formula will take a simpler form:

The minimum distance between pulley axes (minimum center-to-center distance) is:

where Lmin. minimum center distance, mm; D1 and D2. pulley diameters, mm; h. height of the belt profile.

The smaller the centre-to-centre distance, the more the belt flexes during operation and the shorter its service life. it is useful to take the centre-to-centre distance greater than the minimum value Lmin, making it greater the closer the transmission ratio is to one. But to avoid excessive vibration, very long belts should not be used. By the way, the maximum center-to-center distance Lmax is easy to calculate using the formula:

The motor overhaul work is nearing completion. Let’s proceed to the calculation of pulleys of belt transmission of the machine. A little belt transmission terminology.

The main input data we have will be three values. The first value is the rotor speed (shaft) of electric motor 2790 rpm. The second and third are the speeds to be obtained on the secondary shaft. We are interested in two ratings of 1800 and 3500 rpm. Consequently, we will make a two-step pulley.

Note! For starting a three-phase electric motor we will use a frequency converter, so the calculated rotational speeds will be reliable. If the motor is started with capacitors, the rotor speed will be lower than the nominal speed. And at this point, it’s possible to minimize the error by making adjustments. But to do this, you have to start the engine, use a tachometer and measure the current shaft speed.

Our goals are defined, we pass to selection of belt type and to the main calculation. For each of the manufactured belts, regardless of type (V-belt, V-belt or other), there are a number of key characteristics. Which determine the rationale for a particular application. For most projects, the ideal solution is to use a V-belt. Received the name wedge-shaped due to its configuration, it is the type of long closed grooves located along its entire length. The belt’s name comes from the Greek word “poly,” which means many. These grooves are also called ribs or creeks. gradient can be from three to twenty.

V-belts have many advantages over V-belts, such as

• Good flexibility makes it possible to work on small pulleys. Depending on the belt, the minimum diameter can start at ten to twelve millimeters;
• High traction capacity of the belt, hence operating speeds of up to 60 meters per second, compared to 20, maximum 35 meters per second for V-belt pulleys;
• The grip force of a poly-V belt on a flat pulley when the girth angle exceeds 133° is approximately equal to that of a grooved pulley, and as the girth angle increases, the grip force becomes higher. So for drives with gear ratios over three and a small pulley girth angle of 120° to 150°, you can use a flat (no grooves) larger pulley;
• vibration levels are much lower due to the light weight of the belt.

Taking into account all the advantages of poly-V-belts, we will use exactly this type in our constructions. Here is a table of the five basic cross-sections of the most common V-belts (PH, PJ, PK, PL, PM)

## A big home-made circular saw

When making the frame for the upper part of the saw, it is best to use a metal angle with a width of 25 mm. In this case, the rectangle, which will represent the frame of the upper part of the homemade circular saw, should have the dimensions 600×400 mm. Then, in the corners of this quadrangle, four pipes are welded, the diameter of which should be 17 mm, and the height should be approximately 2.2 m.

After that, two angles must be attached to the frame, on which the bearings will later be fixed. The distance between these corners directly depends on the length of the shaft. Clamps are usually used to secure the bearings. It is best if the bearings installed on the homemade circular saw will be of the closed type. This way you don’t have to worry about wood chips getting into the space between the balls, rings and cage. Do not forget to also cut a thread on the very end of the shaft, so that later you can install a cutting disk on it.

The lower part of the circular saw should be made much more massive, which will give it the necessary stability and reliability. Therefore, when making the lower frame you need to take an angle with a width of at least 40 mm. Next, across the frame you need to fix two additional angles, which will later hold the motor of the homemade circular saw. The most suitable motor for the circular saw, made by your own hands, is a three-phase asynchronous motor, with a power not less than 1.5 kW and with 1500 rpm. The pulley handle should be big enough, about 80 mm, and should be placed directly on the shaft itself. In addition, you will need to weld a fairly small metal platform to the frame, which will be placed starter. Large 2.2 m long pipes, which you have previously welded in the corners of the frame, are needed for quality belt tensioning so that the metal winglets will hold the thin pipes.

### Circular saw motor 220v 4kW 3000rpm.

Measurement with a mechanical tachometer requires direct contact with the surface of the object.

Now, in the ready-made support made from pipes, you need to do both the bottom and the top of the home-made saw, and then tighten and tighten the belt with metal winglets. Starting the motor in this model of circular saw with your own hands is carried out with the help of starting capacitors. A 220/36 400 W transformer can be used to overload the motor and increase its torque.

## “Circular saw from a circular saw

Among self-taught carpenters it is believed that the transformation of a manual circular saw into a machine tool is the easiest method of obtaining “three birds” at once, namely:

• High cutting quality guaranteed by the high rotation speed of the saw;
• The shaft, mounted in a commutator motor on bearings, can bear radial forces with pride;
• the ideal (cantilevered) mounting of the blade, it enables a relatively quick replacement of the cutting tool, so there is no need to disassemble the circular saw.

The main advantage of making such a machine is the “native” motor, which guarantees maximum productivity thanks to the ideal torque, optimum revolutions. Other pluses of this solution:

• Relatively simple clamping, allowing quick removal of the saw in case of great need.
• Powerful motor that ensures long operation because of the ability to withstand considerable loads.
• The normal thermal conditions guaranteed by the forced ventilation of this hand tool.
• Sufficient cutting depth can be obtained using large-diameter discs. 60-75 mm. the value that gives a good chance to make high-quality blanks for various products made at home.

### Stand and worktop

Transformation of the hand saw into a circular machine begins with the manufacture of the table (or body-box), on the back side of which then will be attached hand-held power tool so that over the surface of the tabletop protruded part of the cutting edge.

The shape and size of the table is chosen, focusing on the size of future lumber. If you plan to do small billets, then the length is enough 1500 mm, width. 600-700 mm. For the manufacture of the frame of the circular saw is suitable steel angle, which has a width of the shelf, equal to 25-30 mm. The top and bottom of the structure is strengthened with struts, made from the same angle or rebar. This option is optimal to give the frame of the machine maximum rigidity.

For the tabletop often choose laminated chipboard or OSB, some masters stop at plywood, the thickness of this material. 15-20 mm, but you can take a thinner material, and then join together 2 sheets. Elements composing the table top do not necessarily have to be of the same size, have a symmetrical location relative to the bed. The main thing is that the construction is not at risk of tipping over.

A cut is made in the tabletop, designed for extending the blade. The part of the table surface that will be in contact with the cutting tool is often covered with tin plate, metal sheet (aluminum, steel), textolite or plastic. This solution makes it possible to facilitate the movement of the timber as much as possible.

### Modification of the saw control

Such operations can be carried out only in one case: if the tool’s warranty period is over. For the convenience of controlling the circular machine, the contacts of the button and the knob (lever) are led to an external electric switch, which is mounted on the body in a convenient location, but where accidental pressing is completely excluded.

If the owner foresees the possibility of periodically removing hand tools in the future, the contacts are fixed with duct tape or a clamp. In this case, the cord of the circular saw is included in the carrier, equipped with a push-button switch.

### Guiding ruler

It is necessary for precise cutting of material of different widths, so this ruler (stop) must be able to move parallel to the cutting edge. This element is also made from steel angle. Make slots in the tabletop, in which we fix the ends of the guide rail with screws.

A simpler option is a pine board. Its width is 40 mm and its length is 200 mm more than the table’s. First, nuts are pressed into the lower part of the protruding edges, and L-shaped hooks are fixed with screws. After placing the board on the worktop of the circular saw, they are tightened with screws, thanks to them, the hooks are raised and securely fasten the ruler. It is just as easy to move it to any place.

## Frame and frame

Having made the details for the movable parts of the circular, all we need to do now is to make a firm frame and a frame for our circle. In principle, for the home circular stand, you can take the most common materials, such as a piece of thick flat slate. Cut a rectangle out of it and cut a hole under the saw blade, it doesn’t cost anything. But we are supporters of capital construction, so we prefer to take a sheet of metal 3 mm thick for the round frame and a metal angle for a 30 mm frame.

In the picture above you can clearly see which elements make up the frame of the homemade circle. In this case, it is also welded by itself, only as a support is used not static metal angle, but special home tables. The stand is made of two metal tubes of different diameters, which are inserted into each other, so that the round layer can be adjusted in height.

Specialists insist on the welded construction of the round frame, because vibration is bad for the static fasteners created with bolts. Although, if you don’t have welding, as a last resort, you can make the frame from the corners, fastening them together with bolts and nuts. The frame is also better welded to the frame.

## Basic diameters

To calculate the parameters of pulleys, as well as the drive as a whole, different values of diameters are used, so, for the pulley of the V-belt transmission are used:

The calculated diameter is used to calculate the gear ratio, and the outside diameter is used to calculate the dimensions of the drive in the layout of the mechanism.

For toothed belt transmission Ddisc differs from Dnar by the height of the tooth.Gear ratio is also calculated from the Ddcal value.

To calculate the flat belt drive, especially when the rim size is large relative to the profile thickness, we often take D.

## Moving parts

Having finished connection of the motor and checked that it normally rises and drops speeds, you may pass directly to the construction of the circular saw.

Let’s see what movable units, on which the main load falls, we need:

The operation of the drive should be as follows. The motor transmits the rotation to the shaft, on which the small pulley is pressed. On the last is the belt that sends revolutions to the second pulley. At first glance, everything seems simple, but when the installation of the circular saw is carried out, there are many difficulties that must be solved.

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The small pulley is necessarily ground. There are three to four cross grooves in the pulley to give the belt a good grip.

The belt can not be used from an old washing machine, it is enough to take an analogue from another machine. The main thing is that it is durable and has teeth.

## SPA pulleys drawings and dimensions

pulley rotation speed = speed of the shaft on which this pulley is pressed, the transmitted power (in case of belt transmission) can be considered equal to 95% of the nominal, gear ratios and, respectively, rotation speeds are considered as a ratio of diameters of pulleys used. Momentum inverse proportion. All of these are approximate calculations, but if you want accuracy, then download the program and read.

It’s as simple as that. This is changing from a chain to a belt transmission, the input data you need the transmission ratio, power and torque on the shafts, drive shaft spacing, then all this happiness will be entered here and so on.

Works with timing belts, V-belts, multi-ribbed belts and pulleys. Accurately calculates pulley and belt ratios.

We recommend. And lastly. screenshots of program! For example, click on any screen and see what it can do.

## Calculation of V-belt pulley diameter

Please answer how to correctly calculate the diameters of the pulleys, so that the knife shaft of the woodworking machine will rotate at a speed of 3000. 3500 rpm. The speed of the electric motor is 1410 rpm (the motor is three-phase, but will be included in a single-phase network (220 V) with a system of capacitors. V-belt.

### (Eng. Subs) Different Tooth counts for CIRCULAR SAW BLADES (tagalog)

First a few words on the V-belt drive. one of the most common systems for transmitting rotary motion via pulleys and drive belt (such transmissions are used in a wide range of loads and speeds). We produce two types of driving belts. Driving belts (according to GOST 1284) and for autotractor engines (according to GOST 5813). Belts of both types differ from each other in dimensions. Characteristics of some belts are given in tables 1 and 2, cross-section of V-belt is shown in fig. 1. Both types of belts have wedge shape with angle at top of wedge of 40° with tolerance ± 1°. The minimum diameter of the smaller pulley can also be found in tables 1 and 2. When choosing the minimum pulley diameter, however, the linear speed of the belt should also be taken into account and should not exceed 25. 30 m/s, or better (for longer belt life), this speed should be in the range of 8. 12 m/s.

Note. Names of these or those parameters are given in the sketches to Fig. 1.

Note. Names of these or other parameters are given in the figure below. 1.

The diameter of the pulley, depending on the speed of the shaft and the linear speed of the pulley, determined by the formula:

where D1. pulley diameter, mm; V. linear velocity of the pulley, m/s; n. shaft speed, rpm.

It is easy to calculate that for a pulley on the shaft of an electric motor with a speed of 1400 rpm, the minimum diameter of the pulley (step-up gear) at a linear belt speed of 10 m/s will be about 136 mm.

The diameter of the driven pulley is calculated according to the following formula:

where D1 and D2. diameters of driving and driven pulleys, mm; ε. Belt slip ratio of 0.007. 0,02; n1 and n2. rotation speed of driving and driven shafts, rpm.

Since the value of the slip coefficient is very small, the slip correction can be disregarded, i.e. the above formula will take a simpler form:

The minimum distance between the axes of pulleys (minimum center-to-center distance) is

where Lmin. minimum center distance, mm; D1 and D2. pulley diameters, mm; h. belt profile height.

The smaller the centre-to-centre distance, the more the belt will bend during operation and the shorter the service life of the belt. It is reasonable to take the intercenter distance greater than the minimum Lmin, and the larger it is, the closer the transmission ratio is to one. But to avoid excessive vibration do not use very long belts. By the way, the maximum center-to-center distance Lmax is easy to calculate by the formula:

In any case the value of L centre distance depends on the parameters of the belt:

where L. calculated centre-to-centre distance, mm; A1 and A2. additional values which have to be calculated. Now let’s deal with the values A1 and A2. Knowing the diameters of both pulleys and the standard length of the selected belt, it is not at all difficult to determine the values of A1 and A2:

where L. Standard length of the selected belt, mm; D1 and D2. diameters of pulleys, mm.

When designing a plate for mounting the electric motor and the device driven in rotation, for example, a circular saw, it is necessary to provide for the possibility of moving the electric motor on the plate. The point is that the calculation does not give an absolutely accurate distance between the axes of the motor and the saw. In addition, it must be possible to tension the belt and compensate for belt stretching.

Pulley arm configuration and dimensions are shown in Fig. 2. the dimensions in the figure are available in the appendices of the corresponding state standards and in the reference books. But if there are no GOSTs and reference books, all the necessary dimensions of the pulley arm can be roughly determined from the dimensions of the existing V-belt (see Fig.1). Fig. 1), assuming that

Since the case we are interested in is associated with the belt drive, the gear ratio of which is not very high, we do not pay attention to the angle of belt coverage of a smaller pulley in the calculation.

The cone angle of the pulley arm depends on the diameter of the pulley and the brand of the belt. it is clear that the smaller the pulley diameter and the thinner the belt, the more the latter deforms when bending the pulley. The angle between the sides of the pulley cone, depending on the make of pulley and pulley diameter, is given in Table 3.

An important information for belt drive calculation is the drive power, that’s why the corresponding belt selection recommendations are given in the table 4 for certain working conditions.

As a practical guideline, pulleys can be made of any metal. Let’s also add that in order to get the maximum power from a three-phase electric motor plugged into a single-phase network, the capacitance of the capacitors should be as follows:

Cp = 66Pn and Cp = 2Cp = 132Pn,

where Cp. starting capacitor capacity, μF; Cp. the capacitance of the working capacitor, μF; Rn. rated motor power, kW.

For V-belt drives, an important factor that greatly affects belt durability is the parallelism of the pulley rotation axes.

## Calculation of pulley diameters for the V-belt. Online calculator. :: AutoMotoGarage

The motor overhaul is nearly complete. Now let’s start with the calculation of the belt pulleys of the machine. A little belt transmission terminology.

The main input data we will have are three values. The first value is the rotation speed of the rotor (shaft) of the electric motor 2790 revolutions per second. The second and third are the speeds to be obtained on the secondary shaft. We are interested in two ratings of 1800 and 3500 rpm. Consequently, we will make a two-stage pulley.

Note! For starting the three-phase electric motor we will use the frequency converter, so the calculated speeds will be reliable.

In the case of starting the motor by means of capacitors, the values of rotor speed will differ from the nominal one in the lower side. And at this stage it’s possible to reduce the error to a minimum by making corrections.

But to do this, you need to start the engine, use a tachometer and measure the current speed of the shaft.

Our goals are defined, let’s choose the type of belt and proceed to the basic calculation. For each of the manufactured belts, regardless of type (V-belt, poly-V-belt or other), there are a number of key characteristics. Which determine the rationale for using them in a particular application.

The ideal for most projects is to use a V-belt. V-belt gets its name from its configuration, it is a type of long closed grooves located along its entire length. The name of the belt comes from the Greek word “poly,” which means many.

These grooves are also called ribs or creeks. Their number can vary from three to twenty.

The V-belt has many advantages over the V-belt, such as:

• Good flexibility makes it possible to work on small pulleys. Depending on the belt, the minimum diameter can start from ten to twelve millimeters;
• high traction capacity of the belt, hence operating speeds of up to 60 meters per second, versus 20, maximum 35 meters per second for V-belt pulleys;
• V-belt grip with a ribbed pulley above 133° girth angle is about the same as a ribbed pulley and becomes stronger as the girth angle increases. For drives with a transmission ratio greater than three and a small pulley girth angle of 120° to 150° a flat (not grooved) larger pulley can be used;
• Vibration levels are much lower due to the light weight of the belt.

Considering all the advantages of the multiple V-belts we will use them in our designs. Below is a table of the five basic cross sections of the most common poly-V belts (PH, PJ, PK, PL, PM).

The minimum pulley radius is set for a reason, this parameter regulates the life of the belt. The best would be if we slightly depart from the minimum diameter in the larger direction. We have chosen the most common “RK” type belt for a particular application.

The minimum radius for this belt type is 45 millimeters. Taking this into account, we will also be guided by the diameters of available blanks. In our case we have the diameters of 100 and 80 millimeters. We will adjust the diameters of pulleys accordingly.

Let’s start the calculation. Let’s show our initial data again and mark the goals. The speed of the motor shaft is 2790 rpm. Poly V-belt of the RK type. The minimum diameter of the pulley, which is regulated for it, is 45 millimeters, the height of the neutral layer of 1.5 millimeters.

We need to determine the optimal pulley diameters considering the necessary speeds. First secondary shaft speed 1800 rpm, second speed 3500 rpm. Consequently, we have two pairs of pulleys: the first 2790 at 1800 rpm, and the second 2790 at 3500.

The first thing to do is to find the transmission ratio of each of the pairs.

• The formula for determining the gear ratio:
• , Where n1 and n2 are the rotation speeds of the shafts, D1 and D2 are the diameters of the pulleys.
• First pair 2790 / 1800 = 1.55
• Second pair 2790 / 3500 = 0.797
• The following formula is used to determine the diameter of the larger pulley:
• , where h0 is neutral layer of belt, parameter from table above.

For ease of calculation and selection of optimal pulley diameters you can use online calculator.

Instructions on how to use the calculator. First let’s define the units. All parameters except speed are given in millimeters, speed is given in rpm. In the “Belt Neutral Layer” field enter the parameter from the table above column “RK”.

### How to Choose the Correct Cable Pulley #wirerope #pulleys

Let’s enter the value of h0 equal to 1,5 mm. The next field will be used to set the motor shaft speed to 2790 rpm.

In the pulley diameter field enter the value of minimum required for the specific belt type, which in our case is 45 millimeters. Next, we enter the speed parameter at which we want the driven shaft to rotate.

In our case this value is 1800 rpm. Now press button “Calculate”. The diameter of the reciprocating pulley we get in the field, and it is 71.4 millimeters.

Note: If you want to make an estimate for a flat belt or a V-belt, you can neglect the neutral layer of the belt by setting the “ho” field to “0.

We can now (if needed or desired) increase the diameters of the pulleys. For example, it may be necessary to increase the life of the drive belt, or to increase the coefficient of adhesion of the belt-pulley pair. Also large pulleys are sometimes made intentionally to act as a flywheel.

But now we want to maximize fit into the workpiece (we have workpieces with a diameter of 100 and 80 millimeters) and, accordingly, select the best size pulleys.

After several trials of the values we settled on the following diameters D1. 60 millimeters and D2. 94,5 millimeters for the first pair.

For the second pair D1 is 75 millimeters and D2 is 60 millimeters.

Next we proceed to making pulleys. Have a nice work!

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