. .

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 Association 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) and profile 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 specification 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 instruments, 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

Gear Classification and Inspection Handbook for Unassembled Spur and Helical Gears

deviation in alignment is indicated by the sloping most applications the difference is considered dotted line on the chart, located midway between negligiile. However, in the case of extremely the charted lines. modified tooth alignment forms, such as taper on

It should be noted that some generative tooth a cantilever mounted pinion, this difference can alignment checking instruments position the probe become significant. Correction of measured values on centerline, while others offset the probe by the cosine of the pressure angle is appropriate tangentially within the plane of action, thus for such highly modified forms Alternatively, the maintaining true normal tooth contact. Location nominal tooth alignment trace may be defined to of the probe on centerline results in include the modification. This reduces measured measurements tangential to the pitch diameter values to the level of variations only, rather than rather than the base diameter. The difference in variations plus modification. Differences in measured values is related to the cosine of the measurement due to system configuration should pressure angle, or less than 10 percent. Thus, for then be negligible.

(RECOMMENDED) (RECOMMENDED) (NO; RECOMMENDED)

(a) Standard (b) Modified Charts

Fii C-l K Type Chart Reduced at Pitch Diameter

Zero Tolerant

OD

(5)

(4)

(3)

(2)

(1)

C-2 Sloped I( Type

OD

Numbers (1) thru (5) would be the specified Roll Angles

33% C-3 Modified K Chart with Tip and Root Relief Chart

ANSI/AGMA 127 zooo-A88

Gear Classification and Inspection Handbook for Unassembled Spur and Helical Gears

HIGH POINT OF TOOTH CHART

/ MUST BE TANGENT TO

REFERENCE LINE

0 TOLERANCE

0.001

t

FACEWIDTH

Fig C-4 Tolerance Only

SPECIFIED ZONE FOR HIGH POINT\

HIGH POINT OF CROWN TOOTH CHARTMUSTBETANGENTTO REFERENCE LINE IN THIS AREA

EDGE ROUND

REF:NRENCE - O CROWN

TOLERANCE 0.0003

0.0008

* = DRADWW~~;~N

Fig C-5 Crown Tolerance Only

HIGH POINT OF CROWN TOOTH SPECIFIED ZONE CHART MUST BE TANGENT TO

0.0003 MIN. FOR HIGH POINT REFERENCE LINE IN THlS AREA

EDGE ROUND

:~~ -0

0.0008 MAX. UNCTIONAL FACE

* = DRAWlNO DESIGN DIMENSIONS

Fig C-6 Total Tooth Alignment and Crown Tolerance Specification

ANSI/AGh4A 128 2000-A88

Gear Chsification and Inspection Handbook for Unassembled Spur and Helical Gears

FACE

FACEWlDlH

Fig C-7 Chart of ExtemaI Spur Gear Having Crowned Teeth

NOlE:THEHlGHPOiNT OF THE CROWN ARE LOCATED AT AND ARE

As SHOWN BELOW.

NG FOlNlER

Fii C-8 Chart of External He&l Gear Having Crowned Teeth

FACE

Fig C-9 Chart of External Spur Gear Having Tapered Teeth

FACEWIDTH

Fig C-10 Chart of Helical Gear Having Tapered Teeth and a Lead Deviation

AIUWAGMA 129 2000-A88

standards: