. . Gear Classification and Inspection Handbook for Unassembled Spur and Helical Gears Appendix C ProBe and Tooth Alignment Modifkations [This Appendix is provided for informational purposes only and should not be construed as a part of American Gear Manufacturers Associat ion Standard 2000-A88, Gear Classification and Inspection Handbook]. Cl. Purpose. This Appendix is provided to give additional information on modified tooth forms which can be controlled with the Specification of Modified Profile, or Tooth Alignment Inspection Chart Tolerances. C2. Tolerance “K” Charts for Modified Tooth Profiles. In addition to inspecting tooth profiles in general, prome inspection charts are extremely valuable for determining and controlling undercut if present) a nd p rofile modifications such as tip and root relief. The inspection trace of the tooth profile can be interpreted to determine the actual form see Fig 9-20). Specifying a modified “K” Chart can be used to control specific form characteristics. It may be desirable for specifying applications to tighten the tolerance near the pitch diameter to limit hoZIow minus) profile in the center. Fig C-l shows a “K” Chart drawing specif ication of a modified AGMA tolerance with reduced tolerance near the pitch diameter. Figure C-2 shows an example of this modified tolerance with an additional modification specifying a sloped profile. Another modified “K” Chart is illustrated in Fig C-3. In this example, form control is specified for both tip and root relief, using a ‘K” Chart and points determined by specific degrees of roll. NOTE: The use of a modified ‘K” Chart to tolerance the tooth form may add expense to the manufacture, and limit the methods which can be used to achieve the desired results. C3. Tolerance ‘K” Charts for Modified Tooth Alignment Form. Tooth alignment form may be modified to include special characteristics such as crown or taper. It is recommended that tolerances for such special characteristics be superimposed on the tooth alignment tolerance.This is illustrated in Fig C-4 through Fig C-6 for the case of a crown modification. Figure C-4 shows a typical 0.00 1 in) Tooth Alignment “K” Chart tolerance only, and Fig C-5 shows crown tolerance 0.0003 to 0.0008 in) only. Figure C-6 shows the recommended method of specifying tooth alignment and crown tolerances in a single chart. C3.1 Charts of Gears with Crowned Teeth. The amount and position of crowning on gear teeth can be checked on tooth alignment inspection ins truments, as shown by the charts in Figs C-7 and C-8. The charts in Fig C-7 are the adjacent sides of external spur gear teeth, whereas those in Fig C-8 are of the adjacent sides of external helical gear teeth. When both types of gears have the same amount of crowning in the face width, the charts are similar. If the teeth had an alignment variation, there would be a slope in the charted lines in addition to the curvature shown in Figs C-7 and C-8. It should be noted that the high points of the crowning, on adjacent sides of the teeth, lie in the plane normal to the helix, and are therefore displaced in the axial direction. The charts will indicate the location and magnitude of this displacement as shown in Fig C-8. C3.2 Charts of Gears with Tapered Teeth. Tooth alignment inspection insmments can also be used for checking the taper of gear teeth. Charts in Fig C-9 are the adjacent sides of the teeth of an external spur gear having tapered teeth. Here, it will be noticed that the charted lines are not parallel to each other, and that the departure of the charted lines from the datum lines indicate the deviation in parallelism of the sides of the teeth. Figure C-10 shows charts of a left-hand extemal helical gear having the same amount of taper. In the case of the helical teeth however, there is also a minus alignment variation. This is indicated by the charted lines deviating more on one end of the tooth space than on the other. The ANWAGMA 126 2000-A88 Return to Menu