Agma 2000 a88 free download

Diameter, Profile Control. Profile control diameter is the specified diameter of the circle beyond which the tooth profile must conform to Fig Schematic of Composite Action the specified involute curve. The permissible amount of total composite variation.

Eccentricity is the distance between the center of a datum circle and a datum Composite Variation, Tooth-to-Tooth axis of rotation. Double Flank , vq. The greatest change in center distance while the gear being tested is Edge Round. Face width is the length a double flank composite action test see Fig of the gear teeth in an axial plane. In this The total change in center distance each helix.

The functional revolution during double flank composite action face width is that portion of the face width less test see Fig See Surface, Tooth between the extreme values of index variation for a given gear. Total index variation is also Form Diameter. Functional Gear Size.

See Face Width, Teeth. Total index variation within any sector of Functional k teeth is the maximum algebraic difference between extreme values of Index Variation within Functional Profile. See ProfJe, Functional a sector of k teeth. Functional Tooth Thickness. The measurement of Gear Blank. The work piece used for the the change in radial distance over pins or wires manufacture of a gear, prior to machining the gear placed in each tooth space to determine runout teeth.

Index Variation, V,. Index variation is the Inspection Chart. The generated recording displacement of any tooth from its theoretical or trace from an inspection machine used to position, relative to a datum tooth. Measurements display a measured variation of gear geometry. See Profile Tolerance and functional tooth profile, and if made normal to 9. Distinction is made as to the Lead. Lead is the axial advance of a helix algebraic sign of this reading see Fig Fig Lead Lead Variation.

See Tooth Al rnent Pitch, Axial. Master Gear. A gear of known quality, used Pitch, Base, pb. Base pitch of an involute to perform a composite action test. The measurement circle divided by the number of teeth. It is the of the distance taken over a pin positioned in a pitch on the base circle or along the line of action. The Corresponding flanks of involute gear teeth are reference surface may be the reference axis of the parallel curves, and the base pitch is the constant gear, a datum surface, or either one or two pins and fundamental distance between them along a positioned in the tooth space or spaces opposite tangent to the base circle in a transverse plane the first.

This measurement is used to determine see Fig Pitch, Base, Normal. The normal base pitch Mounting Surface. A mounting surface is a in an involute helical gear is the base pitch in the normal plane.

It is the normal distance between surface used to locate and support a gear in its final application. Usually, at least one axial and parallel helical involute surfaces on the line of one radial surface are involved.

Preferably, these action in the normal plane, or is the length of arc on the normal base helix. It is a constant distance same surfaces should be used for manufacturing and inspection operations. Pitch Circle. See Tooth Thickness, Normal. Outside Diameter, Do. Fig Principal Pitches Pitch. Pitch is the distance between similar, equally spaced tooth surfaces along a given line or Pitch, Circular, p. Circular pitch is the arc in the transverse plane see Fig In this distance along a specified pitch circle or pitch line Standard, the use of the single word pitch is to between corresponding profiles of adjacent teeth mean circular pitch.

This can be determined by the average of all pitch measurements of the entire gear taken on successive pairs of teeth, or between corresponding points of adjacent teeth generated by an angular positioning device. Pitch Tolerance. Cylinder of the same angle must be applied to the measured value see diameter as the pitch circle.

Figs and Pitch Diameter, D. Allowable the diameter of a standard pitch circle and is pitch variation is the maximum allowable amount defined by the number of teeth divided by the of pitch variation. It is the permissible plus or transverse diametral pitch, Pd.

It is also defmed minus variation from the true position pitch and it from the pitch of the basic rack of the 20 degrees is the amount shown in the tabies or formulas. Pitch, Diametral, pd. Diametral pitch is the t! The normal Variation diametral pitch is a ratio of the pitch diameter to the number of teeth corrected by the helix angle. Pitch Variation, Normal, vPn. Normal In helical gearing, the diametral pitch can be pitch variation is the plus or minus pitch measured referenced to the normal plane by applying the in the normal plane see Fig for normal cosine of the helix angle.

The total accumulated pitch variation tolerance is the permissible amount of total Pitch, True Position, p. The me position accumulated pitch variation.

Pitch Variation, Total, Accumulated, van. The normal Pitches is equal to the algebraic sum of individual pressure angle is the angle at a point on the pitch plus or minus adjacent pitch variations, VP , wixhin cylinder between the line of pressure which is that sector. For additional information on pressure Plane, Normal. A normal plane is a plane and profile angles see AGMA , Gear normal to a tooth surface at a specified diameter.

NomencZuture, Definition Number 9. At such a point, the normal plane contains the line normal to the tooth surface and the radius Pressure Angle, Transverse, 4. The trans- verse pressure angle is the pressure angle in a from the point to the axis of rotation see Fig On a helical rack, a normal plane is normal transverse plane. See 3. The permissible cross section between the outside circle and the amount of profile variation in the functional root circle. Plus material at surface normal to the pitch surface, such as the the tip which increases the amount of variation transverse, normal, or axial plane see Fig Minus material beyond the start of tip break can be disregarded see Fig Profile Control Diameter.

Quality Number, Q. Fig Functional Profde Reference Tooth. See Datum Tooth. Standard Pitch Circle. A circle defined by the number of teeth and a specified module or diametral pitch see Eq 2. Runout is the maximum variation of the distance between a surface of revolution and a datum surface, measured perpendicularly to that datum surface.

Runout, Axial. Radial runout is the Measurement, Two Probe Device runout measured in a direction perpendicular to the datum axis of rotation. Standard Profile Angle. Radial angle is the angle at the standard pitch circle between a line tangent to the tooth surface and a rtmout tolerance is the permissible amount of radial line of the standard pitch circle see Fig runout.

The profile angle and the pressure angle Single Probe Device. The term spacing is used as a In spur gears the profile angle is considered general term to reference the accuracy with which only in a transverse plane. In helical gears the teeth are positioned around the gear. Spacing has profile angle may be considered in different no numerical value and refers only to a group of planes. In specifications it is essential to use terms numerically valued tooth position measurements that indicate the plane which the profile angle lies, such as pitch or index.

Usually a single Spacing Variation, v,. Spacing variation is gear is stated in terms of the standard pitch and profile angle of the hob or cutter used to generate the difference between any two 2 adjacent its teeth.

See AGhL4 Standard , para 9. The datum surface is the the difference between two 2 adjacent pitch surface used as the basis for measurements. The variation vaiues obtained from a single probe datum surface is established by the specific device. Span Measurement. Span measurement is Surface, Indicated. The indicated surface is the measurement of the distance across several that surface from which the variations from a teeth, along a line tangent to the base cylinder.

It datum surface are measured. The test radius is a number I ANGLE, used as an arithmetic convention established to simplify the determination of the proper test distance, cd, between a master and a work gear for a composite action test. It is used as a measure of the effective size of a gear.

The test radius of the master, plus the test radius of the work gear is the set-up center distance for checking. Test radius is not the same as the operating pitch radii of two tight meshing gears unless both are without variations and have standard tooth thickness. Test Radius Limits. The test radius limits define the allowable range of test radius that takes into account tooth thickness and total composite variations.

Tolerance is the amount by which a specific dimension is permitted Surface, Tooth. The tooth surface forms the to vary. The tolerance is the difference between side of a gear tooth, sometimes called the flank the maximum and minimum limits, and is an see Fig Tooth alignment variation, formerly lead variation , is the difference between the measured tooth alignment and the specified too-h alignments measured normal to the specified tooth alignment X.

IT and the tooth surface on the functional face width see F ig Tolerance values in this standard are F ig Tooth Alignment Variation normal to the tooth surface. Tooth Alignment Trace. The tooth alignment Tooth Profile. See Proftie. Tooth Thickness is the trace recorded on an inspection chart that thickness of a gear tooth at a specified diameter or indicates variations from the reference tooth tooth height. Tooth Thickness, Chordal, tc.

The chordal Total Composite Variation. See Composite Variation, Total. See Index Variation, Total. Transverse Plane. Variation is the measured plus or minus change from the specified value see Fig 1. The normal chordal tooth thickness is the length of the chord subtending a tooth thickness arc in the normal plane.

Tooth Thickness, Circular, t. The circular tooth thickness is the length of arc between two sides of the same gear tooth, on a specified circle Fig Variation see Fig Tooth Thickness, Functional. The tooth Variation, Allowable, A subscript. Tooth Thickness, Normal, t,. The circular tooth thickness in the normal plane. Tooth Thickness Tolerance, tT.

Tooth-to-Tooth Composite Tolerance. See Composite Tolerance, Tooth-to-Tooth. Tooth-to-Tooth Composite Variation. See Pitch Variation, Total Accumulated. Fig Allowable Variation. Manufacturing and Purchasing elements such as manufacturing planning, Considerations machine tool maintenance, cutting tool seiection and maintenance, heat treatment control, and quality assurance pro,mms, as needed, to achieve This Standard provides classification and maintain the necessary gear quality. When tolerances and inspection methods for properly applied, gears manufactured by specific unassembled gears.

This Section presents control techniques will be found to be of very considerations for control of various phases of uniform quality. Therefore, little or no final manufacturing, including the recommended inspection may be necessary for a gear, methods of inspection control. Specific requirements should be stated Using process control, relatively few in the conuactual documents.

For example, tooth size may be evaluated by a 3. It is assumed that these measurements are contract. Specific methods of inspection, sequence on a statistical basis.

Thus, it is possible documentation of Quality Number, and other that a specific gear can pass through the entire geometric tolerances of a gear are normally production process without ever having been considered items which should be specifically inspected. However, the manufacturer of that agreed upon between manufacturer and gear is willing to certify that its quality is equal to purchaser. Gear geometry may inspections. When applications warrant, detailed be inspected by a number of alternate methods.

Upon completion of to measure one or more of the geometric features all manufacturing operations, a specific gear has of a gear fo verify its quality level.

However, a been given an inherent level of accuracy quality. Process control includes number and size as noted in Tables 3-l and The manufacturer shall have the option of among the applicable methods described in this selecting either the individual tolerances of Table Standard and summarized in Table , , or the composite tolerances of Table for 2 The piece of inspection equipment to be gears which are specified by both types of used by the selected inspection method, provided tolerances.

The inspection of manufacturer and purchaser specifies inspection gearing mated in an assembly for a specific of gears, the manufacturer may select: application is beyond the scope of this 1 The inspection method to be used from document.

With Methods. The recommended methods of this technique, the areas that contact can be inspection control for each AGMA Quality observed by coating the teeth with a marking Number and type of inspection are listed in Tables compound and meshing the gears. A judgement through It does not necessarily NOTE: No particular method of inspection indicate compatible tooth shape for loaded or documentation is considered mandatory conditions.

Axial runout may also be indicated by unless specifically agreed upon between a shifting of the tooth contact from side to side, manufacturer and purchaser. When progressively around the gear. This test can applications require inspections beyond include the effect of tooth element variations, those recommended in this Standard, such as a variation in tooth alignment see special inspection methods must be Appendix D.

This Standard does not provide negotiated prior to manufacturing the gear. Quality in Checking tooth contact patterns with a mate or mated gears may also be evaluated by running the master gear is a method of inspection of either gears in a suitable sound testing machine. The assembled gears, or gears mounted on a gear acceptability is characterized by periodic variation testing machine.

It provides an indication of in sound during each revolution, or high levels of compatible tooth shape, both up and down the noise. This Standard does not provide specific tooth profile, and lengthwise on the tooth. It limits for this test, which is normally based on evaluates that portion of the gear tooth surface experience.

The inspection 2 Materials furnished by the purchaser of gearing mated in an assembly for a 3 Matching gears as sets specific application is beyond the scope of 4 Master gears for composite measurement this standard. When specifying the quality of a given gear, there are additional or The items fisted and other special special considerations that should be reviewed.

Table Radial Runout Inspection Control. The total indicator reading includes tooth element variations in addition to runout. Erll 20 0. An individual gear does not tooth thickness of either or both gears of a have backlash. Backlash is only present when one meshing pair, the center distance on which gear mates with another. The theoretical backlash unassembled gears are to be operated must be of a gear set is based on the tooth thickness of designed to provide adequate operating backlash.

The toward increasing backlash. It is required to assure the specified Quality Number. Backlash in a given mesh varies during turned blanks may be found only after some operation as a result of changes in tooth element machining operations have been performed. For variations, speed, temperarure, load, etc. The amount of backlash work performed prior to the discovery of the required depends upon the size of the gears and defect, unless previously agreed otherwise.

Unless otherwise specified, the When heat treating operations are required, maximum tooth thickness of a gear should be less the gear manufacturer shall assume the than the theoretical value by the amount of responsibility for the final quality only when the backlash allowance, including the influence of the material furnished is in accordance with the elemental tolerances.

The minimum tooth agreed upon material specifications. In some applications, it is necessary to provide matched The methods of determining the backlash sets. In such a case, the purchaser must agree on required for individual applications are beyond the details of the additional specifications covering the scope of this Standard See AGMA Applications Unless an allowance for backlash is made in the requiring high accuracy gearing may necessitate.

Considerations profiles and helix angles such that the matched set for certain gearing applications may require a high is satisfactory for the application. Matched sets degree of accuracy in the angular position of the can be provided, but usually at extra cost. For such applications, a specification of the allowable amount of index variation should NOTE: This Standard provides tolerances be established in addition to the Quality Number for unassembled gears only.

The inspection shown herein. The interpretation specific application is beyond the scope of of data should be carefully conducted in this Standard. However, for high accuracy accordance with the inspection methods indicated gearing, the matching process can be fully in Section 9, and with the instruction of the satisfactory even when individual element measuring equipment manufacturer. Unless tolerances are exceeded.

The matching otherwise contractually agreed upon, the process for such gears sold as pairs assumes interpretation of data shall be the prerogative of greater importance than the individual the gear manufacturer.

The tolerances, 3. When a composite check is specified, a Standard prevail unless contractual agreements master gear becomes necessary. A master gear is a between the manufacturer and purchaser contain gear of known quality, designed specifically to specific exceptions. The variation. The design, accuracy, and cost of a quality of a gear is determined by the lowest master gear must be negotiated between the AGMA Quality Number obtained by evaluating manufacturer and purchaser.

Usually, a specific the gear using the criteria of this Standard. If the gear is master gear must be scheduled to be available to be accepted by individual element inspections, when the manufactured gear is to be inspected by it is acceptable if the following variations do not composite measurements. Provides information on manufacturing procedures, master gears, measuring methods and practices.

Appendix material provides guidance on specifying levels and information on additional methods of gear inspection. Partial replacement of AGMA Your Alert Profile lists the documents that will be monitored. If the document is revised or amended, you will be notified by email. This equipment can be accurate to within millionths of an inch and is frequently installed in environmentally agma a88 rooms. In this process a heated steel gear is placed in a carburizing medium, containing carbon that diffuses into the surface to its case depthenriching the surface beyond the rest of the steel in the gear.

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For certain if agma a88 need agma a88 control a special element of the standard, it should be specified. Manufacturing Certification. Specifying an AGMA Quality Numberor inspection criteria which is in excess of thatrequired by the application may increase the costunnecessarily.

The manufacturing of gearing to a specifiedqualitymayormaynotinclude specificinspections. Process Control. Upon completion ofall manufacturing operations, a specific gear hasbeen given an inherent level of accuracy quality. Upon completion of all manufacturing operations, a specific gear has been given an inherent level of accuracy quality.

This level of accuracy was established during the manufacturing process, and is totally independent of any final inspection. Process control includes A?.?. SIiAGMA 16 elements such as manufacturing planning, machine tool maintenance, cutting tool seiection and maintenance, heat treatment control, and quality assurance pro,mms, as needed, to achieve and maintain the necessary gear quality. When properly applied, gears manufactured by specific control techniques will be found to be of very uniform quality.

Therefore, little or no final inspection may be necessary for a gear, particularly in some classification levels; assurance of the necessary quality level having been built-in through careful manufacturing control at each step.

NOTE: Documentation may be deemed unnecessary for products manufactured under process control when inspection records are not specified in the purchase contract. For example, tooth size may be evaluated by a measurement over pins, a span measurement, or another similar measurement which is usually checked on only two or three sections of a given gear.

It is assumed that these measurements are representative of all of the teeth on the gear. Gears made in production quantities may be inspected at various steps in their manufacturing sequence on a statistical basis. Thus, it is possible that a specific gear can pass through the entire production process without ever having been inspected.

However, the manufacturer of that gear is willing to certify that its quality is equal to those gears that were inspected, based on his confidence in his process control. Gear geometry may be inspected by a number of alternate methods. The selection of the particular method depends not only on the magnitude of the tolerance and the size of the gear, but also on production quantities, equipment available, accuracy qf gear blanks, and inspection costs.

The manufacturer or the purchaser may wish to measure one or more of the geometric features of a gear fo verify its quality level. However, a gear which is specified to an AGMA Quality Number must meet all the individual tolerance requirements applicable fo the particular quality number and size as noted in Tables 3-l and Normally, the individual tolerances of pitch, proftie, and tooth alignment shall apply to both sides of the teeth, unless only one side is specified as the loaded side.

The inspection of gearing mated in an assembly for a specific application is beyond the scope of this document. Gear Classification and Inspection Handbook for Unassembled Spur and Helical Gears NOTE: No particular method of inspection or documentation is considered mandatory unless specifically agreed upon between manufacturer and purchaser. When applications require inspections beyond those recommended in this Standard, special inspection methods must be negotiated prior to manufacturing the gear.

With this technique, the areas that contact can be observed by coating the teeth with a marking compound and meshing the gears. A judgement of compatibility may be made by the position and size of the contact area.

It does not necessarily indicate compatible tooth shape for loaded conditions. Axial runout may also be indicated by a shifting of the tooth contact from side to side, progressively around the gear.

This test can include the effect of tooth element variations, such as a variation in tooth alignment see Appendix D. This Standard does not provide tolerances relating these tesrs to gear quality. Checking tooth contact patterns with a mate or master gear is a method of inspection of either assembled gears, or gears mounted on a gear testing machine. It provides an indication of compatible tooth shape, both up and down the tooth profile, and lengthwise on the tooth.

It evaluates that portion of the gear tooth surface 3. Quality in mated gears may also be evaluated by running the gears in a suitable sound testing machine. The acceptability is characterized by periodic variation in sound during each revolution, or high levels of noise. This Standard does not provide specific limits for this test, which is normally based on experience.

The recommended methods of inspection control for each AGMA Quality Number and type of inspection are listed in Tables through The inspection of gearing mated in an assembly for a specific application is beyond the scope of this standard.

When specifying the quality of a given gear, there are additional or special considerations that should be reviewed. These considerations may include items such as: The items fisted and other special considerations should be reviewed and agreed upon between manufacturer and purchaser. The total indicator reading includes tooth element variations in addition to runout. An individual gear does not have backlash.

Backlash is only present when one gear mates with another. The theoretical backlash of a gear set is based on the tooth thickness of each member in mesh, as well as the center distance at which the gears are assembled.

The actual backlash will be a function of the tolerances on tooth thickness, runout, lead, profile, and center distance. Some backlash must be present in all power transmitting gear meshes. It is required to assure that the nondriving sides of the teeth do not make contact. Backlash in a given mesh varies during operation as a result of changes in tooth element variations, speed, temperarure, load, etc.

Adequate backlash should be present during static conditions, when it can be measured, to assure sufficient backlash under load at the most adverse operating condition. The amount of backlash required depends upon the size of the gears and the application. Unless otherwise specified, the maximum tooth thickness of a gear should be less than the theoretical value by the amount of backlash allowance, including the influence of the elemental tolerances.

The minimum tooth thickness must be less than the maximum tooth thickness by the tooth thickness tolerances. The methods of determining the backlash required for individual applications are beyond the scope of this Standard See AGMA Unless an allowance for backlash is made in the ANWAGMA 22 tooth thickness of either or both gears of a meshing pair, the center distance on which unassembled gears are to be operated must be designed to provide adequate operating backlash.

The tolerance on center distance should be toward increasing backlash. Gear blank dimensions supplied by the purchaser should be mutually agreed upon, which will permit the gear manufacturer to hold the tolerances for the specified Quality Number.

Certain defects in the rough material or turned blanks may be found only after some machining operations have been performed. For example, inclusions, blow holes, or other defects may appear in the material when cutting the teeth. If defects are serious enough to cause rejections, the gear manufacturer must be reimbursed for the work performed prior to the discovery of the defect, unless previously agreed otherwise.

When heat treating operations are required, the gear manufacturer shall assume the responsibility for the final quality only when the material furnished is in accordance with the agreed upon material specifications.

In some applications, it is necessary to provide matched sets. In such a case, the purchaser must agree on the details of the additional specifications covering how the matching is to be verified. Applications requiring high accuracy gearing may necessitate A Gear Classification and Inspection Handbook for Unassembled Spur and Helical Gears the matching, or modifying, of pinion and gear profiles and helix angles such that the matched set is satisfactory for the application.

Matched sets can be provided, but usually at extra cost. The inspection of gearing mated in an assembly for a specific application is beyond the scope of this Standard. However, for high accuracy gearing, the matching process can be fully satisfactory even when individual element tolerances are exceeded. The matching process for such gears sold as pairs assumes greater importance than the individual absolute measurements. When a composite check is specified, a master gear becomes necessary.

A master gear is a gear of known quality, designed specifically to mesh with the gear to be inspected for composite variation. The design, accuracy, and cost of a master gear must be negotiated between the manufacturer and purchaser. Usually, a specific master is required for each different production gear design.

For 3. If satisfactory, replace with similar material and quality. If improved performance is desired, modifications of material, heat treatment, and quality level should be considered. Consult with the manufacturer for appropriate recommendations. Conditions may require that one or more of the individual elements or composite tolerances be of a lower or higher Quality Number than the other tolerances.

In such cases, it is possible to modify the Quality Number to include a Quality Number for each gear element or composite tolerance see Appendix A.

Considerations for certain gearing applications may require a high degree of accuracy in the angular position of the teeth. For such applications, a specification of the allowable amount of index variation should be established in addition to the Quality Number shown herein. The interpretation of data should be carefully conducted in accordance with the inspection methods indicated in Section 9, and with the instruction of the measuring equipment manufacturer.

Unless otherwise contractually agreed upon, the interpretation of data shall be the prerogative of the gear manufacturer. The tolerances, methods, and definitions contained in this Standard prevail unless contractual agreements between the manufacturer and purchaser contain specific exceptions. The quality of a gear is determined by the lowest AGMA Quality Number obtained by evaluating the gear using the criteria of this Standard. If the gear is to be accepted by means of a composite action test double flank , it is acceptable if the following variations do not exceed the tolerances for the specified AGMA Quality Number: 1 Tooth-to-Tooth Composite Variation 2 Total Composite Variation NOTE: Within the body of this Standard, all references to composite variation are understood to apply to a double flank composite action test.

An example of how to establish an 4. Thi-ceen Quality Classes of accuracy are provided in this Standard, numbered Q3 through Q15 in order of increasing precision. Tooth Thickness are provided in this Standard. C, and D, specify permissible of decreasing tolerance. See Sections 1 and 3. See Sections 4 and 5. See Section 4 and paragraph 6. Hyphen l Required to separate tooth thickness and materials designation letters.

Material Designation l Two letter group indicating type of material. See Section 7. Treatment and Hardness Designator l Indicates the type of heat treatment, and the hardness range. The hardness is designated by a pair of numerals indicating the hardness range for that material. Designation 4. The AGMA Quality Number defines the accuracy of a gear in either of two methods: 1 The element analytical inspections 2 The composite action test, double flank Evaluation.

The 4. When composite action tolerance is specified it shall be in lieu of any element inspection. In the case where individual Quality -Numbers have been specified for each of the characteristics, the quality is designated by stating the values for both characteristics. In certain may be additional applications there characteristics that may require tolerances in order to assure satisfactory performance. For example, if dimensions for tooth thickness, tolerances or total index variation, or surface finish tolerances are desirable in order to assure satisfactory performance in special applications, such dimensions and tolerances should appear on drawings or purchase specifications.

Methods of measuring some of these characteristics are discussed in Section 9, and in the Appendices. In the case where individual Quality Numbers for each of the elements have been specified, the quality is designated by stating the values for the elements specified.

The tolerances for each item that govern the quality of gears are calculated by the equations given in Section 5, and presented in tabular form in Section 6. Values outside the limits of either the tables or the equations are beyond the scope of this Standard, and should not be extrapolated. The specific tolerances of such gears must be agreed upon by the buyer and the seller. Within the body of the tables, values not shown may be obtained by interpolation. However, the values obtained through interpolation may not be as accurate as those obtained using the equations, and should be used only as approximations.

Formulas Tolerances for Gear Accuracy 5. The following gear accuracy tolerance formulas are reconsuucted from the AGMA Tables and equations are provided to determine tolerances. The equations allow the determination of tolerances for sires which are within the formuia limits. Conversely, a thick tooth causes a minus reading. This change may be computed as two times the addendum comparator reading times the tangenf of the normal profile angle of the instrument.

This 9. The distance measured is the sum of n-1 base pitches normal base pitches for helical gears , plus the thickness of one tooth at the base cylinder. Measurements are not affected by outside diameter variations or runout see Fig The measurement are: of of Span span 1 Span measurement cannot be applied when a combination of high helix angle and narrow face width prevent the caliper from spanning a sufficient number of teeth.

Measurements are erroneous if attempted on a portion of the profile which had been modified from true involute shape. In addition, the gear rolling fixture requires that the center distance be calibrated.

When the master gear and the work gear are each mounted on a arbor, the gear rolling fixture must have a dual set of centers. In addition, the operator should have two precision set-up arbors, having a length within 10 percent of that length of the work gear and master gear holding arbors.

These arbors should not exceed 0. This center type rolling fixture is set up as follows: 9. Pins afford an accurate method of measuring tooth thickness of gears of any diameter within the capacity of micrometers available see Fig Measurements are affected by variations in tooth spacing and profile. Obtain the actual testing radius, L, from the master gear or from its current 9.

This method utilizes a composite action test double flank gear rolling fixture and a calibrated master gear. This indicates the ftmctional tooth thickness, which includes the effects of all tooth variations. Arbor sets having a diameter difference of 0.

Ball-bushing arbors with interference fits can also be used. It is important when composite checking gears in this quality range, to remove all possible looseness between the arbors and bores of both master gear and inspected gear, by one of these methods, so that additional nmout is not reflected in the composite chart due to inaccurate mounting.

Journal-type gears are tested on their own centers. This is another measure of work gear functional tooth thickness with a master gear. The test center distance is fixed and it must be accurately determined that the axes are parallel and in the same plane. The backlash of the test set should be measured in at least two places, preferably four, at equal intervals around the gear.

Repeat the procedure using the minimum stack of blocks, L. Common Quality Number for All Elements. To determine the AGMA Class Number for the given application, experience, and material and treatment knowledge are necessary. Figure shows examples of class numbers where all gear element tolerances are of the same class. Example: Assume a Control Gear Aerospace having teeth, 48 diametral pitch 0. Step 4. Refer to Table 7-l. Step 5.

Conditions may require that one or more of the individual gear-element tolerances be of a different Quality Number than the other element tolerances. Step 1. Determine the desired Quality Number from experience or analysis. This indicates that Quality Number QlO is typical for the application.