| Applicable Accuracy Standard | ISO 1328-1 for cylindrical gear tooth flanks, or AGMA 2015-1 for AGMA accuracy classification. | Select one primary classification system for acceptance and identify any secondary reference standard separately. | Standard designation, edition or revision, accuracy grade, inspection date, and measurement conditions. | Different standards use different definitions, symbols, grade ranges, and evaluation methods. |
| ISO 1328 Accuracy Grade | Specify the required ISO 1328-1 grade for the gear pair or individual gear. | ISO 1328-1 uses grades from 1 to 11; a lower numerical grade represents tighter geometric accuracy. | Declared ISO grade and measured deviations for profile, helix, pitch, and runout-related characteristics. | Prevents suppliers from describing a gear only as “precision” without a measurable classification. |
| AGMA 2015 Accuracy Grade | Specify the required AGMA 2015-1 accuracy grade when AGMA classification is used. | AGMA 2015-1 uses grades from 3 to 15; a lower numerical grade represents tighter accuracy. | Declared AGMA grade, measured characteristics, inspection method, and report traceability. | Provides a recognized AGMA acceptance framework for buyers and suppliers using inch- or metric-based gear production systems. |
| Grade Conversion | Do not request an unqualified “ISO-to-AGMA equivalent.” State the governing standard and acceptance grade. | ISO 1328 and AGMA 2015 grades should not be treated as automatically interchangeable; any correlation must be technically justified for the specific gear. | Written conversion rationale, if a cross-reference is used, including gear size, module or diametral pitch, face width, and measured deviations. | Nominal grade numbers and tolerance calculations are not directly comparable across the two systems. |
| Gear Type and Geometry | Define spur or helical gear, normal module or diametral pitch, number of teeth, helix angle, pressure angle, face width, reference diameter, and handedness. | Use a fully dimensioned drawing or controlled digital model; identify datum surfaces and mounting references. | Actual measured geometry compared with drawing values and permitted deviations. | Accuracy tolerances depend on gear geometry and inspection conditions, not on the accuracy grade alone. |
| Profile Accuracy | Require total profile deviation and profile form or slope components where applicable. | Specify the active profile evaluation range, profile modification requirements, and whether tip relief or root relief is permitted. | Profile graph, total profile deviation, form deviation, slope deviation, evaluation range, and tolerance result. | Profile errors influence contact ratio, transmission smoothness, noise, load distribution, and local tooth contact. |
| Helix or Lead Accuracy | Require total helix deviation and relevant helix form or slope components for helical and face-width-sensitive gears. | State the usable face-width evaluation range and any intentional crowning or end relief. | Helix or lead graph, total helix deviation, form or slope values, evaluation width, and pass/fail result. | Lead errors can concentrate load at one side of the tooth and accelerate wear or edge contact. |
| Pitch Accuracy | Require single pitch deviation and cumulative pitch deviation. | Evaluate both tooth-to-tooth variation and cumulative indexing error; do not rely on only one pitch value. | Single pitch deviation, adjacent pitch variation where reported, cumulative pitch deviation, tooth-by-tooth data, and tolerance limits. | Pitch errors affect transmission error, mesh timing, vibration, and rotational accuracy. |
| Runout and Radial Composite Accuracy | Require radial runout or total runout measurement relative to the defined datum axis. Use composite testing when specified by the design. | Define the datum bore, shaft reference, or mounting arbor and identify whether the result is single-flank or double-flank testing. | Runout graph or tooth-by-tooth results, datum definition, measurement direction, and actual value versus limit. | Runout can create periodic transmission error, uneven backlash, and localized loading even when individual tooth flanks appear acceptable. |
| Backlash and Tooth Thickness | Specify operating backlash, tooth thickness or space width, and the reference temperature. | Use a defined backlash range rather than a single nominal value; include the mating gear, center distance, and assembly condition. | Measured tooth thickness or span measurement, backlash calculation or measurement, temperature, and mating-gear assumptions. | Correct accuracy does not guarantee correct assembly if tooth thickness, center distance, or backlash is uncontrolled. |
| Material and Heat Treatment | Specify material grade, hardness range, case depth or through-hardening requirement, and heat-treatment condition. | For hardened gears, define hardness locations, effective case depth method, and allowable distortion after heat treatment. | Material certificate, hardness results, case-depth results where applicable, heat-treatment batch identification, and distortion measurements. | Material and heat treatment determine load capacity, wear resistance, dimensional stability, and service life. |
| Surface Finish | Specify tooth-flank roughness parameters and measurement direction, such as Ra or Rz where appropriate. | Set finish requirements according to sliding velocity, lubrication regime, load, and whether the gear is shaved, ground, honed, or milled. | Surface roughness values, instrument traceability, measurement location, filter or cutoff settings, and acceptance limits. | Surface finish affects friction, scuffing risk, noise, lubricant film behavior, and running-in. |
| Inspection Equipment | Require calibrated gear-measuring equipment suitable for the gear diameter, module or diametral pitch, and accuracy grade. | Use a coordinate or dedicated gear-measuring system for profile, helix, and pitch; use a calibrated runout setup for datum-related checks. | Equipment identification, calibration status, software or measurement method, probe information, and inspection operator or laboratory record. | Inspection results are only useful when the equipment range, calibration, and measurement method are appropriate. |
| Measurement Conditions | Define reference temperature, stabilization time, mounting method, datum axis, and gear orientation. | Use a controlled reference temperature, commonly 20 °C for dimensional metrology, unless the purchase specification states otherwise. | Temperature, humidity where relevant, stabilization period, mounting arbor, datum definition, and alignment procedure. | Thermal expansion, mounting error, and axis misalignment can materially influence reported gear deviations. |
| Report Data Format | Require both a summary result and the underlying measured values for each inspected characteristic. | Accept a report only when it shows nominal value, tolerance, actual value, deviation, grade, and pass/fail status. | Unique gear serial or lot identification, drawing revision, operator, date, standard, grade, measured data, and approval signature. | A complete report supports incoming inspection, supplier comparison, root-cause analysis, and future repeat orders. |
| Sampling Plan | Define first-article, pre-production, lot, and periodic requalification inspection requirements. | Inspect every gear for critical dimensions and use full gear accuracy inspection for first article and defined production samples. | Sample size, sampling basis, inspected serial numbers, lot number, rejected quantity, and corrective-action records. | A single inspection report cannot demonstrate stable production capability without an agreed sampling and traceability plan. |
| Application-Based Selection | Link the required accuracy grade to speed, torque, noise target, positioning accuracy, duty cycle, and service life. | Use tighter grades for high-speed, low-noise, precision-positioning, or highly synchronized applications; avoid over-specifying accuracy when the system cannot use it. | Engineering basis, application limits, required grade, and verification results under the intended assembly conditions. | Accuracy grade is one part of gear performance; design, load capacity, lubrication, alignment, and housing stiffness are equally important. |
