Dissertations and Theses @ UNI


Open Access Dissertation


Gearing, Spiral--Dynamics; Gearing, Spur--Dynamics; Steel--Heat treatment;


The purpose of this study was to determine the relationships between selected gear features and distortions due to heat treatment. An extensive review of the literature indicated that studies on gear distortions were mainly metallurgically oriented, and the relationships between gear geometrical features and dimensional distortions due to heat treatment had not been investigated.

This investigation obtained data from actual gear size adjustments that had been collected from many years of experimentations at the John Deere Component Works (JDCW), Waterloo, Iowa. Gear data were converted to uniform files and were classified, retrieved, and analyzed by computerized systems. Two groups of gears (helical and spur) were selected and analyzed. Each group contained gears made of a similar grade of steel and recived similar heat treatment.

The selected features included:

(1) Working pressure angle.

(2) Helix angle (helical gears).

(3) Module.

(4) Tooth width.

(5) Outside diameter.

(6) Bore.

(7) Internal spline number of teeth.

(8) Internal spline pressure angle.

(9) Internal spline module.

(10) Approximate body/tooth volume ratio.

Dimensional distortions due to heat treatment were the differences in measurement taken before and after heat treatment. These measurements were taken from the following dimensions:

(1) Tooth thickness.

(2) Lead.

(3) Profile.

(4) Crown.

(5) Outside diameter.

(6) Bore.

(7) Internal spline tooth thickness.

Eleven major research questions for helical gears and 10 major research questions for spur gears were addressed. Each research question had one to nine sub-questions that inquired the relationship between one gear feature and one dimensional distortion. Answers to these research questions were presented in graphic form with statistical findings. The graphic analyses included scater diagram presenting the dimensional distortions for each gear feature. The multiple regression statistical method was used to determine the correlation coefficient for each gear feature and each dimensional distortion. In addition, step-wise multiple regression was used to determine the relationship of a single dimensional distortion and a set of gear features.

For helical gears made of standard steel with a grade number of 1524 that had been carburized and quenched in hot or cold oil significant (p < .05) correlation coefficients were found. These significatn correlation coefficients were between: (a) gear working pressure angle, module, tooth width, outside diameter, bore, approximate body/tooth volume ratio, and tooth thickness distortion, and (b) approximate body/tooth volume ratio and internal spline tooth thickness distortion.

Significant (p < .05) correlation coefficients were also found for spur gears composed of standard steel with a grade number of 1518 that had been carburized, slow cooled, received induction heating of the teeth, and quenched in cold oil. These significant correlation coefficients were between: (a) gear outside diameter, approximate body/tooth volume ratio, and tooth thickness distortion, and (b) cutter pressure angle and profile distortion. The answers to the research questions that had significant correlation coefficients were presented graphically, augmented by statistical findings. Each graph included the line of "best fit" showing the relationship of one gear feature and a dimensional distortion. The values for the slope and the intercept of the line of best fit were also provided.

Year of Submission


Degree Name

Doctor of Industrial Technology


Department of Industrial Technology

First Advisor

Patrick W. Miller, Advisor

Second Advisor

Rex W. Pershing, Co-Advisor

Date Original


Object Description

1 PDF file (xi, 104 pages)



File Format