Handbooks Din 3990 Pdf

DIN 3990 PDF

Monday, July 8, 2019

For calculations specified in ISO (Z02a) or DIN (Z02). The ISO or DIN standards specify that tooth trace modifications are performed in a reasonable. Sign In · View Account▹ · Home; DIN Secure PDF. ℹ Add to Cart. Printed Edition + PDF; Immediate download; $; Add to Cart. the calculation of load capacity with respect to DIN, AGMA- standard and. ISO-recommendations,. − the calculation of gearing elastic deformation.

Din 3990 Pdf

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I need a copy of DIN and/or ISO for gear analysis. I work in a paper for gear failure Can you help by adding an. But the common calculation methods according to ISO and DIN are extended size factor for the calculation method according to DIN and ISO. Since the latest German standard, DIN , (6) issubstantially similar to ISO ,. a detailed discus- sionof DIN is excluded. The new British standard.

Legende zu Bild 4. Aplication factor KA has not been used in the expression 3 , since it is taken into. They are checked with Safety factor tooth root bending stresses. Variantenberechnungen im Maschinen- und Anlagenbau - VCmaster ; 0,80 mm. Die im Katalog verwendeten Berechnungsgrundlage ist DIN Methode B.

Welle—Nabe—Verbindungen - n.

Einfederung bei Dynamikfaktor innere Dynamik. Berechnungsgang nach DIN bestimmen.

For the calculation you can consider the addendum chamfer. Meshing interferences can be removed by the addendum chamfer.

Addendum chamfer Please Note: If you define the geometry of the gear pair, you are able to look at the tooth form. The many methods of making gear teeth must be considered as well.

The calculation program distinguishes between gear-tooth cutting and gear hobbing. Input mask for tool data Please note: If you want to add some own notes, comments or a description, then use the comment line. Basically, the selection of the tool depends on the gear type external or internal gears. The external gears can be produced by cutting wherein the gear cutting tool is a hob. For internal gears a gear shaper cutter is used see section 7.

Selection of tool Hob Generation The hobbing is the most widely used method of cutting gear teeth. The hobbing process is quite advantageous in cutting gears with very wide facewidth.

A very high degree of tooth-spacing accuracy can be obtained with hobbing. With regard to accuracy, hobbing is superior to the other cutting processes. A wide variety of sizes and kinds of hobbing machines are used. The rotating hob has a series of rack teeth arranged in a spiral around the outside of a cylinder, so it cuts several gear teeth at one time.

To generate the full width of the gear, the hob slowly traverses the face of the gear as it rotates. Thus, the hob has a basic rotary motion and an unidirectional traverse at right angles. Both movements are relatively simple to effect, resulting in a very accurate process. Field of Application of the Hob: Hob and gear shaper cutter Gear Shaper Generation The shaping process is a gear-cutting method in which the cutting tool is shaped like a pinion.

If a gear is provided with cutting clearance and is hardened, it may be used as a generating tool in a gear shaper. The cutter reciprocates while it and the gear blank are rotated together at the angular-velocity ratio corresponding to the number of teeth on the cutter and the gear. The teeth on the gear cutter are appropriately relieved to form cutting edges on one face.

Although the shaping process is not suitable for the direct cutting of ultra-precision gears and generally is not as highly rated as hobbing, it can produce precision quality gears. Usually it is a more rapid process than hobbing. Two outstanding features of shaping involve shouldered and internal gears. For internal gears, the shaping process is the only basic method of tooth generation.

Field of Application of the Gear Shaper Cutter: Recommended for internal and external spur and helical gears Racks Special gearings, e.

In case internal gears cannot be shaped with a gear shaper cutter, the tooth form calculation is still possible by using the constructed involute. This specifically applies for applications in the precision mechanics. This method allows a generation of the tooth form with a constant root fillet radius. Constructed Involute Representation of Hob and Gear Shaper Cutter The representation shows either the hob basic rack profile or the gear shaper cutter tooth profile.

The radio buttons enable you to choose one of the graphical representation. Tool 7. According to DIN a rack is the basic rack profile. A gear with an infinite number of teeth will have straight lines for both the pitch and the base circles.

The involute profile will be a straight line. The rack can be used to determine the basic parameters. Racks can be both spur and helical. A rack will mesh with all gears of the same pitch. The pressure angle and the gears pitch radius remain constant regardless of changes in the relative position of the gear and rack. The following standard basic rack profiles are available for your calculation.

Choose your profile from the listbox.

Calculation of load capacity cylindrical gears; calculation of pitting resistance

ISO 53 Profile D: Care should be taken to avoid creating notches in the fillet during finishing which could create stress concentrations. When part of the involute profile of a gear tooth is cut away near its base, the tooth is said to be undercut.

By using a protuberance tool an undercut near the root can be generated. Grinding notches at the tooth flank can be avoided during the grinding.

That provides relief for subsequent finishing operations see section 7. Selection of the protuberance tools You can select the following profiles: Prot 1. Now you can modify the basic rack profile.

Own input Modification of the Basic Rack Profile In case you use special tools, the eAssistant offers an easy and comfortable solution. Button for the tool dimensioning Here you can change the tip and the root diameter for gear 1 and gear 2. Tool dimensioning 7. Undercut is the loss of profile in the vicinity of involute start at the base circle due to tool cutter action in generating teeth with low numbers of teeth.

The protuberance cuts an undercut at the root of the gear tooth. The protuberance design is also used in some cases to permit the sides of gear teeth to be ground without having to grind the root fillet.

Shaper cutters can be made with a protuberance at the tip. This provides a desirable relief for a shaving tool. Radius corners: The corners of cutter teeth are radiused and produce a controlled fillet in the root corners of the gear being generated. A smooth surface is created, notch effects are decreased and strength is increased.

The gearing tools for modified tooth forms may be used only in a specified range of number of teeth. The range of number of teeth itself is dependent upon the number of teeth of the working wheel and the allowed tolerances.

Determination of the Amount of the Protuberance from the Height of the Protuberance Flank The following equation determines the amount of the protuberance. In case the height of the protuberance flank is given and not the amount of the protuberance, the amount of the protuberance may be calculated by this equation. The following figure shows a representation: Height of the protuberance flank To avoid grinding steps, a deviation in the tooth root area of the profile is a common and allowed method.

Because of a grinding stock allowance, an undercut must be allowed. Hence, a larger tooth root thickness is necessary. The following table shows some determination of the undercut dependent upon the module.

Undercut for Ground Gears Dependent upon Module 2 Module Allowance Protuberance Addendum Coefficient Edge Radius 2 0, 0, 2, 0, 2,5 0, 0, 3, 0, 3 0, 0, 4, 0, 4 0, 0, 5, 1, 5 0, 0, 7, 1, 6 0, 0, 8, 1, 7 0, 0, 10, 1, 2 from: Linke, H.: The allowance is the smallest distance between the involutes and the pre-machining having the same root diameter.

In case you select the tool basic rack profile with protuberance, the allowance refers to the tooth flank. If the allowance of the tool basic rack profile is selected without protuberance, then tooth flank and tooth root get the allowance. The eAssistant provides the following allowances for the grinding of a gear: Cutter tooth profile is built up on the tip to provide an undercut near the root of the gear being generated.

Maximum Machining Allowances 3 Allowance per Tooth Flank Manufacturing Process 0,05 0,10 mm Finishing operation by cold rolling, gear shaving, honing, lapping 0,05 to 0,5 1,5 mm Grinding, profile grinding, honing 0,5 mm, pre-cutting Primary shaping, forming, cutting with geometrically determined edges except shaving, grinding and profile grinding in special cases 3 from: Hence, a deviation from the nominal size has to be allowed. For a lot of applications the gear and the pinion of a pair must be independently manufactured and meshed without any modifications.

That means, the parts have to be separately replaceable. Input of allowances 7. In all fields of gearing, the control of gear accuracy is essential. Several classes or grades of accuracy can be set. High accuracy grades can be set for a long-life, high speed gears. Lower accuracy grades will cover medium- or slow-speed grades.

Niemann, G.: Maschinenelemente, Vol. Tolerances according to the manufacturing process Select the appropriate quality between 1 and 12 by using the following listbox. Listbox for the selection of quality The following table provides some reference values for the selection of the quality, tolerances for gearings made of metal and plastics: For the system of fits for gear transmissions letters are used to indicate the deviation from basic nominal size, a number defines the width.

Own input 7. The magnitude of tooth thickness and its tolerance is a direct measure of backlash when the gear is assembled with its mate. Dimensional changes, due to thermal expansion, do not allow a zero-backlash assembly. The tooth thickness allowance has to be determined that no jamming occurs. To prevent that jamming of gears during the operation, it is necessary to decrease tooth thickness by a minimum amount and.

Lower and upper tooth thickness allowances for gear 1 and gear 2 The tooth thickness allowances for teeth of external and internal gearings have to be negative.

Then a backlash occurs find more information on the backlash in section 7. The eAssistant offers the possibility to specify the tooth thickness allowances based on measured data or given test dimensions. Calculation of tooth thickness allowances Activate gear 1 and gear 2 and enter the input values. Now you can change the tooth space allowances.

The actual measurement of the span measurement gets smaller for external gears by negative allowances for a zero-backlash assembly.

The upper and lower tooth space allowance are displayed as well. For an own input of the tooth thickness allowances, the tooth space allowances can be defined as well. Therefore, you can change the tooth space allowances. Tooth space allowance for gear 1 and gear 2 7. The sizing of gears may be controlled by double-flank composite checks and centre distance settings corresponding to maximum and minimum tooth thickness specifications.

Different measurement methods are used: At pitch circle chordal , Span measurement across several teeth, Measurement over pins or balls that are placed in diametrically opposed tooth spaces, Check of the centre distance allowance with zero-backlash engagement by using a master gear in a flank roll tester. In the following you get some information on the widely used measurement methods: Span measurement Measurement by diameter over balls or pins, the measurement by using balls and pins Span Measurement across Several Teeth Span measurement is the measurement of the distance across several teeth in a normal plane.

As long as the measuring device has parallel measuring surfaces that contact on an unmodified portion of the involute, the measurement will be along a line tangent to the base cylinder.

It is a widely used method for gauging the tooth thickness by using the span measurement. The tooth thickness of spur or helical gears is often measured with calipers. An advantage is that the dimensions can be influenced during the manufacturing.

Span measurement The calculation program determines the number of teeth for the span measurement number of teeth across the span measurement has to be gauged. If you click the button again, the previous input value appears. Number of teeth for the span measurement Tooth Thickness Measurement by Diameter over Pins or Balls The tooth thickness is often checked by measurement over pins or balls. The pins or balls are placed in diametrically opposed tooth spaces even number of teeth or nearest to it odd number of teeth.

Measurement over pins is the measurement of the distance taken over a pin positioned in a tooth space and a reference surface. The reference surface may be the reference axis of the gear, a datum surface or either one or two pins positioned in the tooth space or spaces opposite the first. The measurement over pins is only used for spur gears and external helical gears. For the measurement values a distinction is made between: Measurement over balls Measurement over pins Measurement over pins for a spur gear Measurement over pins for external helical gears with even number of teeth Measurement over pins for external helical gears with odd number of teeth For an external gear the measurement over balls is the largest outer measure.

The two balls are placed in diametrically opposed tooth spaces. The balls have to be in the same plane perpendicular to a gear axis. For an internal gear see figure: The internal gear is generally checked for tooth thickness with measuring pins, like the external gear. However, the measurement is made between the pins instead of over pins. Measurement over balls: External spur gear with evennumber of teeth Measurement over balls: External spur gear with oddnumber of teeth Measurement over balls: Internal spur gear with oddnumber of teeth The eAssistant already specifies the diameter of ball or pin for the test dimensions.

Enter your own input value for the diameter. If you click on the button once again, the previous input value appears.

Diameter of ball or pin Please Note: The center distance and the gear fits have an important influence on the backlash. The gear fit selection defines the tolerances of the centre distance with the backlash.

The gear fit selection provides only one tolerance field. These conform to the ISO basic tolerances. The backlash is dependent upon the tooth thickness allowances and the tooth space allowances.

Hence, if you change the centre distance, then the backlash is changed, too. Now you are able to enter your own centre distance allowances.

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Confirm your entries with Enter. The backlashes are automatically determined.

The allowances are indicated with to get no improper major allowances from the nominal centre distances with gears having several axes. Centre distance allowance 7. For that, a proper backlash must be provided for the mesh to avoid jamming of the gears. The eAssistant offers three different backlashes: Backlash normal plane Besides errors in manufacturing and assembling, the variation in backlash will depend considerably on the tooth thickness tolerances and centre distance of the gears.

The DIN system represents a standard centre distance and provides the backlash by changing the tooth thickness. The backlash between the meshing teeth adjusts the deviations of the tooth thicknesses, centre distance and tooth form using the tooth thickness and tooth space allowances. The lowest tooth thickness allowance indicates the maximum backlash, the upper tooth thickness allowance indicates the minimum backlash.

In addition to the tooth thickness allowance and centre distance allowance, errors in profile and pitch are also factors to consider in the specification of the amount of backlash.

Please note: The backlash depends also on thermal expansions, deformation of elementes and displacement of casing. These impacts must be considered for the determination of the tooth thickness. The backlash pitch diameter may be the length of the pitch circle arc in which the gear rotate against its mating gear.

Backlash pitch diameter 7. The radial backlash matters especially for very small modules m 0,6 mm. Radial backlash 7. For the presentation you can select the lower, upper and mean allowances for the tooth thickness, tip diameter and centre distance.

When you define the geometry for the gear pair, then you can have a look at the tooth form at any time. Tooth form Please Note: In case you change the tooth thickness allowance or the centre distance allowance in the tooth form mask, then the last modification is taken over to the DXF output.

The Section 7. DXF output 7. Cylindrical gear pair Please Note: Please keep in mind that you can check the backlash and the mesh ratio only in the presentation of the mesh. The gear mesh will be discussed in Section 7. You get a larger representation of the gear tooth form. Now you can see the detailed tooth mesh. Detail view of the mesh Please Note: The representation of the tooth mesh allows you to look at the tooth thickness allowances, the tip diameter and centre distance allowances as well the tooth mesh and to check the influence of these values.

The tooth form mask provides various functions. Find a short description of these functions in the following section. Rotating angle Rotation of the driving gear counter-clockwise Rotation of the driving gear clockwise 7. Rotation The continuous rotation of the driving gear counter-clockwise The continuous rotation of the driving gear clockwise The rotation is stopped. All changes are displayed immediately. For the representation of the tooth mesh, select the lower, upper and mean tooth thickness allowances for gear 1 and gear 2.

The active input is grayed out and disabled. Click on the left arrow and you will get the representation for the lower tooth thickness allowance. The right arrow shows the representation for the upper tooth thickness allowance. The middle button displays the mean tooth thickness allowance. At the first start of the tooth form, you will get the mean tooth thickness allowance as a standard feature. The tooth thickness allowances can be defined between the lower and upper allowance.

Tooth thickness allowance Please Note: For the representation of the tooth mesh, select the lower, upper and mean tip diameter allowances for gear 1 and gear 2. Click on the left arrow and you will get the representation for the lower tip diameter allowance. The right arrow shows the representation for the upper tip diameter allowance. The middle button displays the mean tip diameter allowance. At the first start of the tooth form, you will get the mean tip diameter allowance as a standard feature.

Tip diameter allowance Please Note: You can check the operation of the gears by using various centre distance settings.

For the representation of the tooth mesh, select the lower, upper and mean centre distance allowances for gear 1 and gear 2. Click on the left arrow and you will get the representation for the lower centre distance allowance.

The right arrow shows the representation for the upper centre distance allowance. The middle button displays the mean centre distance allowance.

At the first start of the tooth form, you will get the mean centre distance allowance as a standard feature. Centre distance allowances Please Note: The strength is determined by the loads, the geometry of gearing as well as selected materials. The calculation of the load capacity is about the proof of the following strength factors that result from the above-mentioned forms of damage: Pitting, scuffing or wear may weaken the tooth so that it breaks.

The slow progress of the fracture apparently causes the metal to break like brittle material. A tear or grinding notch may cause a tooth breakage. Gear tooth fractures ordinarily start in the root fillet.

The tooth breakage can destroy an entire gearing and leads to a failure of the gearing. Sometimes a new tooth will break as a result of severe overload or a serious defect in the tooth structure. According to DIN , an operation with a reduced load is possible after a tooth breakage, if just a small portion of a tooth broke off and the other parts of the gearing are intact.

For a high load capacity of the tooth root, the following methods are advantageous: This is caused by high tooth loads leading to excessive surface stress, a high local temperature due to high rubbing speeds or inadequate lubrication.

The cracking of the surface develops, spreads and ultimately results in small bits breaking out of the tooth surface. But it is often possible to get some years of service out of gears that have pitted rather extensively.

For a high load capacity of the tooth flank, the following methods are advantageous: Tears and scratches appear on the rubbing surface of the teeth.

Scuffing is an important form of damage leading to component replacements in lubricated mechanical systems. Compared with tooth breakage and pitting, it is not a fatigue failure, it can come very quickly. A short overload can lead to scuffing and the gearing fails. Scuffing is apt to occur when the gears are first put into operation because the teeth have not sufficient operating time to develop smooth surfaces.

Due to the scuffing, the temperature, the forces and the noise increase, the gear teeth finally break off. The following factors may influence the occurrence of scuffing: Gear material Lubrication Surface condition of tooth flanks Sliding velocity Load Impurities in a lubricant After the occurrence of scuffing, high-speed gears apt to additional dynamic forces that cause usually pitting or tooth breakage.

The high surface temperature may cause a breakdown of the lubricating film. The following factors support scuffing: High loads Kind of lubrication: Non-alloy oil protects less against scuffing than E. Larger contact ratio and tooth alignment errors may cause local stresses by impacts and unbalanced carrying. For a high scuffing load capacity, the following methods are advantageous: There are two different types of scuffing - cold and hot scuffing.

Both types describe a damage on the flank. The scuffing problem is not limited to high-speed gears. Scuffing can also occur on slow-speed gears. The slow-speed scuffing is called cold scuffing and the high-speed hot scuffing. Cold scuffing is not often observed. Hence, all further comments and information refer to hot scuffing. Hence, you can check the load capacity of tooth root and tooth flank as well as the scuffing fast and easily.

The scuffing safeties are determined according to the integral and flash temperature method. The material properties, the endurance, face load factor, application factor as well as the kind of lubrication and the selected lubrication are taken into consideration for the calculation. There are extended input options to influence the number of load changes or the roughness. A grinding notch can be integrated into the calculation and the mode of operation can be selected.

You will notice that all input fields or listboxes are disabled. In case you do not need the calculation for load capacity, the calculation can be disabled. Thus, the size of the calculation report becomes smaller. Activate the calculation for load capacity 7. Eventually, the material database opens. Material database In order for gears to achieve their intended performance, life and reliability, the selection of a suitable material is very important.

Steel is the most common material that is used for gears. There are a number of steels used for gears, ranging from plain carbon steels through the highly alloyed steels from low to high carbon contents.

The choice will depend upon a number of factors, including size, service and design. For pinion and gear, the same hardened and tempered steel may be used.

It has to be kept in mind that unhardened gears with equal hardness should not be meshed with each other because scuffing is apt to occur. A hardened or nidrided gear smoothes the tooth flanks of the hardened and tempered mating gear, reduces the form deviations and increases the load capacity of the tooth flank.

For a mating of hardened gears, no hardness difference is necessary. The final selection of the material should be based upon an understanding of the material properties and application requirements. Hardening and tempering differs from hardening by annealing at high temperatures. The temperature range for hardening and tempering ranges from to C while after hardening, parts are annealed at a low temperature. On the other hand, a distinction is made between the material. However, there is no well-defined limit between hardening and tempering and hardening.

Kind of Material Steel casting: Steel casting belongs to the ferrous metals that include carbon up to max. Due to a higher melting temperature, steel casting is more difficult to cast than cast iron.

Steel casting is cheaper than ground or forged gears. Steel is the most common material and is used for medium and high-loaded gears. Nidrided steel: Nitriding is adding nitrogen to solid iron-base alloys by heating the steel in contact with ammonia gas or other suitable nitrogenous material.

This process is used to harden the surface of gears.

Cylindrical gear pairs according to DIN / ISO and further standards

Case-hardened steel: Case-hardened steel is a quality and high-grade steel with low carbon content. Case-hardened steel is usually formed by diffusing carbon carburization , nitrogen nitriding into the outer layer of the steel at high temperature and then heat treating the surface layer to the desired hardness.

When the steel is cooled rapidly by quenching, the higher carbon content on the outer surface becomes hard while the core remains soft and tough. Blackheart malleable cast iron pearlitic structure: Malleable cast iron is a heat-treated iron carbon alloy. Two groups of malleable cast iron are specified, whiteheart and blackheart cast iron. Blackheart malleable cast iron is used for parts with a complex shape, in which a high durability, shock resistance and good machining are important. Malleable cast iron is used for smaller dimensions and has got a higher strength and toughness than steel castings.

DIN MDesign Esempio Spur Gear, Gear Rack

Cast iron with spheroidal graphite pearlitic structure, bainitic structure, ferritic structure: It is extremely rare that the maximum carbon content is higher than 4. Cast iron is a low-priced material. However, cast iron has less toughness and ductility than steel. Cast iron with spheroidal graphite can be used for parts with higher vibration stress.

Heat-treated steel: Hardening and tempering is a heat-treating technique for steels by quenching from the hardness temperature and annealing at a high temperature so that the toughness is increased significantly.

At the same time, a higher elastic limit is reached. Annealing temperatures and times differ for different materials and with properties desired, steel is usually held for several hours at about C to C. Some steels have to be cooled very quickly Annealing: Gray cast iron: Gray cast iron is used for complex shapes and offers low cost and an easy machinability. It provides excellent damping properties but it is a disadvantage that the load capacity is very low.

Please Note: Your inputs will be saved to the calculation file. Please be advised that changing the material will delete your defined inputs and you have to enter the inputs again.

Own input of a material Application Factor The application factor evaluates the external dynamic forces that affect the gearing. These additional forces are largely dependent on the characteristics of the driving and driven machines as well as the masses and stiffness of the system, including shafts and couplings used in service.

Because scuffing is not a fatigue failure, the application factor shall consider the stronger influence of several load peaks during the calculation of the scuffing load capacity.

Several load peaks affect directly only the flank temperature. Because of that, the same application factor can be used for the calculation of the scuffing load capacity as well as of the load capacity of the tooth root and tooth flank.

The application factor is determined by experience. The following table gives some values according to DIN DIN Part 1, December , p. Light Shocks: Moderate Shocks: Heavy Shocks: Click on this button and the above-mentioned table opens. You will find this button next to several input fields. The question mark button Face Load Factor The face load factor takes into account the effects of the non-uniform distribution of load over the gear facewidth on the surface stress , on the tooth root stress and on the scuffing.

In case you already use a defined face load factor, you can save the certain factor to a template file. Then the calculation module starts with the individual face load factor.

When you click on the calculator symbol, the input mask for the face load factor opens. You will notice that the lower input fields and listboxes are disabled. There is a listbox next to the input field for the face load factor. Listbox with the selection of DIN As soon as you select this entry from the listbox, the remaining input fields and listboxes are enabled.

The face load factor is determined automatically but you still cannot take over the value to the main mask. In order to take over the calculated value, you have to add further inputs from the input mask for the face load factor. However, there is the possibility to take over the value, determined according to DIN, to the main mask without changing the extensive settings.

When you click on the calculator button next to the face load factor, the above-mentioned input mask opens. The face load factor is displayed in the input field. Take over the face load factor Mesh Misalignment The path of teeth is marked by the path of tooth traces. The tooth trace is the section of a tooth flank with the reference surface. The mesh misalignment considers all influences of manufacturing, assembly and deformation that may intensify and compensate each other. Using this method, portions of the mesh misalignment are considered caused by a deformation of pinion and pinion shaft as well as manufacturing inaccuracies.

The mesh misalignment is a misalignment due to manufacturing inaccuracies and is dependent upon the gear accuracy and the facewidth of the gear. Mesh misalignment Please Note: The selection and input fields are enabled.

User-defined inputs for the mesh misalignment are also possible. User-defined selection Position of Tooth Contact Pattern The tooth contact pattern gives some insight into the required geometry and accuracy of gears.

While rolling off each other, a tooth flank will not come into contact with every point of its mating flank. A tooth contact pattern is a representation of contact surfaces of two engaged tooth flanks of gear pair. Under operating conditions, an even load distribution over the facewidth and tooth depth is to be accomplished.

The value is determined again according to DIN. If your values are out of range of the DIN, you will get an information in the message window. The allowances are determined according to DIN. Such a modification of the tip diameter have an effect on the tip diameter. A certain clearance between the gears is necessary for a smooth operation.

There is the tip clearance and the backlash. Standard gears have got a basic rack profile with a addendum coefficient or a tool basic rack profile with.

The dedendum coefficient of the basic rack profile or the addendum coefficient of the tool basic rack profile has to be larger due to ensure that tip and root circle of the gears are not in contact.

Backlash If the gears are of standard tooth proportion design and operate on standard center distance, they would function ideally with neither backlash nor jamming.

The general purpose of backlash is to prevent gears from jamming and making contact on both sides of their teeth simultaneously. Any error in machining which tends to increase the possibility of jamming makes it necessary to increase the amount of backlash. Consequently, the smaller the amount of backlash, the more accurate must be the machining of the gears. Runout of both gears, errors in profile, pitch, tooth thickness, helix angle and centre distance - all are factors to consider in the specification of the amount of backlash.

In order to obtain the amount of backlash desired, it is necessary to change the tooth thickness or tooth space allowances please see also section 7.A gear with an infinite number of teeth will have straight lines for both the pitch and the base circles. Now you have to define 6 kW for the pinion to dimension the gearing. For the representation of the tooth mesh, select the lower, upper and mean tooth thickness allowances for gear 1 and gear 2.

Lower and upper tooth thickness allowances for gear 1 and gear 2 The tooth thickness allowances for teeth of external and internal gearings have to be negative. Meshing interferences can be removed by the addendum chamfer.

Heat-treated steel: