AGMA-2111-A98-1998.pdf
ANSIJAGMA 2111 - A98 Metric Edition of ANSUAGMA 2011-A98 AMERICAN NATIONAL STANDARD Cylindrical Wormgearing Tolerance and Inspection Methods (Metric) AGMA STANDARD COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services American Nat ion al Standard Cylindrical Wormgearing Tolerance and Inspection Methods (Metric) (Metric Edition of ANSi/AGMA 201 1 -A98) Approval of an American National Standard requires verification by ANSI that the require- ments for due process, consensus and other criteria for approval have been met by the standards developer. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement has been reached by directly and materially affected interests. Substantial agreement means much more than a simple majority, but not necessarily una- nimity. Consensus requires that all views and objections be considered, and that a concerted effort be made toward their resolution. The use of American National Standards is completely voluntary; their existence does not in any respect preclude anyone, whether he has approved the standards or not, from manufacturing, marketing, purchasing or using products, processes or procedures not conforming to the standards. The American National Standards Institute does not develop standards and will in no circumstances give an interpretation of any American National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the American National Standards Institute. Requests for interpre- tation of this standard should be addressed to the American Gear Manufacturers Associ at¡ on. CAUTION NOTICE: AGMA technical publications are subject to constant improvement, revision or withdrawal as dictated by experience. Any person who refers to any AGMA Technical Publication should be sure that the publication is the latest available from the Association on the subject matter. Fables or other self-supporting sections may be quoted or extracted. Credit lines should read: Extracted from AN SI/AGMA 211 1 -A98, Cy/hdricai Wormgearing Toerance andIn- spection Methods, with the permission of the publisher, the American Gear Manufacturers Association, 1500 King Street, Suite 201 , Alexandria, Virginia 2231 4.1 ANSI/AGMA 21 11 -A98 Approved October 1, 1998 ABSTRACT This standard describes and defines variations that may occur in unassembled wormgearing. it displays mea- suring methods and practices, giving suitable warnings if a preferred probe cannot be used. The applicability of single or double flank composite testing is discussed, using a reference gear. Tooth thickness measurement is shown using direct measurement as well as the use of measurements over wires or pins. Equations for the maximum variations are given for the stated ranges, as a function of size, pitch and tolerance grade. Published by American Gear Manufacturers Association 1500 King Street, Suite 201, Alexandria, Virginia 22314 Copyright O 1998 by American Gear Manufacturers Association Ail rights reserved. No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without prior written permission of the publisher. Printed in the United States of America ISBN: 1-55589-717-7 II COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services AMERICAN NATIONAL STANDARD ANSIIAGMA 2111 -A98 Contents Page Foreword . iv 1 Scope 1 2 Symbols. terms and definitions . 1 3 Manufacturing and purchasing considerations 5 4 5 Equations for worm and wormgear tolerances . 20 Measuring methods and practices 7 Tables 1 Symbolsused . 2 Figures 1 Functional part of the profile . cutoff points. drop-off region 4 2 Lead and lead form variation . 4 3 Worm thread runout inspection. Vrl . 7 4 Worm pitch variation inspection. Vpl - method A 8 5 Worm pitch variation inspection. Vpl - method B 9 6 7 Worm thread profile inspection. V+l 10 Worm thread profile tolerance band. v+T1 . 10 8 Worm thread lead inspection. vil 11 Wormgear tooth runout. VQ . 12 9 10 Location of probe - wormgear pitch variation. Vp2 13 11 Two probedevice . 13 12 Schematic of single probe device 14 13 Relationchips of pitch variation. Vp2. and accumulated pitch variation. V, . . 15 14 Pitch variation. Vp2. graphical data from two probe device . 15 15 Pitch variation Vp2. and accumulated pitch variation. VW2: graphical data from single probe device . 15 16 Schematic of a double flank wormgear tester 17 17 Schematic of a single flank wormgear tester 17 18 Thread thickness measurement by means of a gear tooth caliper 18 19 Thread thickness measurement over pins 18 Annexes A Inspection tolerance tables . . . 21 Bibliography . 43 . 111 COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services ANSI/AGMA2111-A98 AMERICAN NATIONAL STANDARD Foreword The foreword, footnotes and annexes, if any, in this document are provided for informational purposes only and are not to be construed as a part of ANWAGMA Standard 2 1 1 1 498, Cylindrical Worngearing Tolerance and Inspection Methods (Metric) . The purpose of this standard is to establish geometrical accuracy communication between a manufacturer and purchaser of unassembled cylindrical wormgearing with axes at right angles. AGMA 390.02 September 1964 was a replacement for AGMA 234.01 for fine pitch wormgearing. ANWAGMA 2000-A88 is a partial revision of AGMA 390.03, but does not cover wormgearing. AGMA 390.03a of 1988 still only covered fine pitch wormgearing. ANSIIAGMA 2111498 then is a replacement for AGMA 390.03a for fine pitch wormgearing. In addition, it also covers coarse pitch wormgearing. The Cylindrical Wormgearing Committee began working on this standard in August, 1993. At that time, it was determined the International Standards Organizations (ISO) method for tolerance grades would be used in this standard. ANWAGMA 2111-A98 was approved by the AGMA membership in June, 1998 and approved as an American National standard on October 1, 1998. Suggestions for improvement of this standard will be welcome. They should be sent to the American Gear Manufacturers Association, 1500 King Street, Suite 201, Alexandria, Virginia 22314. iv COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services AMERICAN NATIONAL STANDARD ANSIIAGMA 2111 -A98 PERSONNEL of the AGMA Cylindrical Wormgearing Committee Chairman: J.R. DeMarais . Bison Gear this level of accuracy was established during the manufacturing process and is totally independent of any final inspection. Process control includes elements such as manufacturing planning, maintenance of machine tools, cutting tool selection and maintenance, heat treatment control and quality assurance programs, as needed, to achieve and maintain the necessary gear accuracy. When properly applied, gears manufactured by specific control techniques will be found to have consistent accuracy. Therefore, care- ful manufacturing control at each step of the process should eliminate the need for final inspection. However, based on appropriate confidence in the applied process control, the manufacturer of that gear must be able to certify that its tolerance grade is at least equal to that of the gears that were inspected. NOTE: Documentation may be deemed unnecessary for products manufactured under process control when inspection records are not specified in the purchase contract. 3.3 Inspection methods Gear geometry may be inspected by a number of methods as described in clause 4. The selection of the particular method depends on the magnitude of the tolerance, the size of the gear, the production quantities, equipment available, accuracy of gear blanks and inspection costs. When prior agreement between the manufacturer and purchaser specifies inspection of gears, the manufacturer may select: - the inspection method to be used from among the applicable methods described in this standard; - the piece of inspection equipment to be used by the selected inspection method, provided it is properly calibrated; - the number of teeth or threads to be mea- sured to assure conformance to the specified tolerance grade. 3.4 Additional considerations In addition to tolerance grade for certain applica- tions, other or special considerations may be re- quired. These may include items such as: backlash allowances in tooth thickness; materials furnished by the purchaser; matching gears as sets; reference gears for composite measurement; replacement gearing; contact pattern. The listed items and other special considerations are to be reviewed and agreed upon by the manufacturer and purchaser. 3.4.1 Backlash allowance An individual gear does not have backlash. Back- lash 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 mounting distance at which the gears are assembled. The actual backlash will also be a function of the tolerances on tooth thickness, runout, lead, profile and mounting distance. The methods of determining the backlash required for individual applications are beyond the scope of this standard (for additional information see ANSI/ AGMA 6022-C93, Design Manual for Cylindrical Wormgearing). 3.4.2 Material furnished by the purchaser Gear blanks supplied by the purchaser shall meet the specifications mutually agreed upon between manufacturer and purchaser to permit the gear manufacturer to hold the tolerances for the specified tolerance grade. 3.4.3 Matching gears as sets Matched sets are required in some applications and can be provided, but usually at extra cost. In such cases, the purchaser must agree on the details of the additional specifications concerning how the match- ing is to be performed and verified. Applications requiring high accuracy gearing may necessitate the matching or modifying of worm and gear profiles such that the matched set is satisfactory for the appl ication. NOTE: This standard provides tolerances for unas- sembled gears only. 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 individ- ual absolute measurements. 6 COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services ANSI/AGMA2111-A98 AMERICAN NATIONAL STANDARD 3.4.4 Reference gears for composite measurement When a composite check is specified, a reference gear becomes necessary. The design, accuracy, AGMA tolerance grade validation procedure and cost of a reference gear shall be negotiated between the manufacturer and purchaser. A specific refer- ence gear is required for each different production gear design. The reference gear shall be available when the manufactured gear is to be inspected by composite measurements. 3.4.5 Contact pattern Contact pattern is beyond the scope of this standard. For information on contact pattern, see ANWAGMA 6022-C93. 3.4.6 Replacement gearing the individual tolerance requirements applicable to that tolerance grade. 4 Measuring methods and practices This section describes the recommended methods and practices used for the inspection of worms and wormgears. Practices and inspection methods which are recognized and accepted throughout the wormgear industry as being reliable are covered and should provide accurate and repeatable measure- ments when correctly used. Experienced personnel, using calibrated instruments in a suitable environ- ment, are required. No particular method of inspection or document is considered mandatory unless agreed upon by the purchaser and manufacturer. For replacement gearing, the performance obtained 4.1 Worm thread radial runout, V r l from the previous gearing must be evaluated. If satisfactory, replace with similar material and accuracy. If improved performance is required, modifications of material, heat treatment and toler- ance grade may be considered. Consult with the 3.5 Acceptance criteria The tolerances and definitions contained in this standard prevail unless contractual agreements between the manufacturer and purchaser contain specific exceptions. 3.6 Evaluation of tolerance grade The manufacturer or the purchaser may wish to measure one or more of the geometric features of a gear to v e r i its accuracy. However, a gear which is specified to an AGMA tolerance grade must meet all 0 manufacturer for recommendations. The worm thread radial runout may be measured by positioning the worm reference bearing diameters on precision V-Blocks on a flat inspection table as shown in figure 3. A shell worm is mounted on a precision arbor. Using the reference bearing diame- ter or the arbor diameter at each end to establish the reference axis of the worm, the height of a pin that contacts only the thread flanks is measured. The worm is rotated as many times as necessary until the maximum reading over the pin is obtained. A minimum of four (4) readings at approximately 90“ of rotation of the worm starting from the maximurn reading is then recorded. The radial runout, Vrl, is the difference between the high and low readings. These measurements should be done first near one end of the thread and repeated near the other end of the thread to assure that the axis of the thread is parallel to the axis of the shaft bearings or arbor. Figure 3 - Worm thread runout inspection, V r 1 7 COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services COPYRIGHT American Gear Manufacturers Association, Inc. Licensed by Information Handling Services ANSIIAGMA 2111 -A98 AMERICAN NATIONAL STANDARD Worm axial section 4.1.1 Causes of worm thread radial runout, Vrl Reference The principle cause of radial runout is eccentrictty which, in turn, is caused by forming the threads from shaft centers in one machine and turning, grinding, or boring the locating reference diameters from shaft centers in another machine. However, this measure- ment method may include the effects of the follow- ing: thread - thread thickness variations; - ence diameters or the threads themselves; thread Worm axial section Reference out-of-roundness of either the l
