Dr. Hermann J. Stadtfeld

Dr. Hermann J. Stadtfeld received in 1978 his B.S. and in 1982 his M.S. in mechanical engineering at the Technical University in Aachen, Germany; upon receiving his Doctorate, he remained as a research scientist at the University's Machine Tool Laboratory. In 1987, he accepted the position of head of engineering and R&D of the Bevel Gear Machine Tool Division of Oerlikon Buehrle AG in Zurich and, in 1992, returned to academia as visiting professor at the Rochester Institute of Technology. Dr. Stadtfeld returned to the commercial workplace in 1994 — joining The Gleason Works — also in Rochester — first as director of R&D, and, in 1996, as vice president R&D. During a three-year hiatus (2002-2005) from Gleason, he established a gear research company in Germany while simultaneously accepting a professorship to teach gear technology courses at the University of Ilmenau. Stadtfeld subsequently returned to the Gleason Corporation in 2005, where he currently holds the position of vice president, bevel gear technology and R&D. A prolific author (and frequent contributor to Gear Technology), Dr. Stadtfeld has published more than 200 technical papers and 10 books on bevel gear technology; he also controls more than 50 international patents on gear design, gear process, tools and machinery. (Bio last updated 2018-02-05 Contact Randy Stott, Managing Editor, with changes.)

Articles by Hermann J. Stadtfeld

  • Three-Face Blade Technology (November/December 2017)
    The author compares the standard two-face blade technology with the three-face blade technology for manufacturing bevel gears.
  • Friction Coefficient of Differently Treated Steel Surfaces (November/December 2017)
    A reader asks about ion-nitride finished shafts and the proper friction coefficient to be used for calculations.
  • MicroPulse and MicroShift for Ground Bevel Gearsets (July 2017)
    Grinding of bevel and hypoid gears creates on the surface a roughness structure with lines that are parallel to the root. Imperfections of those lines often repeat on preceding teeth, leading to a magnification of the amplitudes above the tooth mesh frequency and their higher harmonics. This phenomenon is known in grinding and has led in many cylindrical gear applications to an additional finishing operation (honing). Until now, in bevel and hypoid gear grinding, a short time lapping of pinion and gear after the grinding operation, is the only possibility to change the surface structure from the strongly root line oriented roughness lines to a diffuse structure.
  • Backlash in Bevel and Hypoid Gears (July 2017)
    What is the relationship between angular backlash or mean normal backlash change and the axial movement of the ring gear in bevel and hypoid gears?
  • Universal Hobs (March/April 2017)
    Another expert takes a crack at a previously answered question about double-helical gears and universal hobs.
  • Helical Gear Systems (August 2016)
    In terms of the tooth thickness, should we use the formulation with respect to normal or transverse coordinate system? When normalizing this thickness in order to normalize the backlash (backlash parameter), we should divide by the circular pitch. Thus, when normalizing, should this circular pitch be defined in the normal or traverse coordinate system, depending on which formulation has been used? Is the backlash parameter always defined with respect to the tangential plane or normal plane for helical gears?
  • Bevel Gear Cutting Methods (June 2016)
    THE FINAL CHAPTER This is the last in the series of chapters excerpted from Dr. Hermann J. Stadtfeld's Gleason Bevel Gear Technology - a book written for specialists in planning, engineering, gear design and manufacturing. The work also addresses the technical information needs of researchers, scientists and students who deal with the theory and practice of bevel gears and other angular gear systems. While all of the above groups are of course of invaluable importance to the gear industry, it is surely the students who hold the key to its future. And with that knowledge it is reassuring to hear from Dr. Stadtfeld of the enthusiastic response he has received from younger readers of these chapter installments.
  • Rules for Optimal Basic Design of Bevel Gears (May 2016)
    Bevel Gear Technology Chapter 6
  • Practical Gear Characteristics: Process Characteristics of the Most Popular Cutting Methods (March/April 2016)
    The cutting process consists of either a roll only (only generating motion), a plunge only or a combination of plunging and rolling. The material removal and flank forming due to a pure generating motion is demonstrated in the simplified sketch in Figure 1 in four steps. In the start roll position (step 1), the cutter profile has not yet contacted the work. A rotation of the work around its axis (indicated by the rotation arrow) is coupled with a rotation of the cutter around the axis of the generating gear (indicated by the vertical arrow) and initiates a generating motion between the not-yet-existing tooth slot of the work and the cutter head (which symbolizes one tooth of the generating gear).
  • Hard-Finishing Spiral Bevel Gears (March/April 2016)
    Could you explain to me the difference between spiral bevel gear process face hobbing-lapping, face milling-grinding and Klingelnberg HPG? Which one is better for noise, load capacity and quality?
  • The Importance of Profile Shift, Root Angle Correction and Cutter Head Tilt (January/February 2016)
    Chapter 2, Continued In the previous sections, development of conjugate, face milled as well as face hobbed bevel gearsets - including the application of profile and length crowning - was demonstrated. It was mentioned during that demonstration that in order to optimize the common surface area, where pinion and gear flanks have meshing contact (common flank working area), a profile shift must be introduced. This concluding section of chapter 2 explains the principle of profile shift; i.e. - how it is applied to bevel and hypoid gears and then expands on profile side shift, and the frequently used root angle correction which - from its gear theoretical understanding - is a variable profile shift that changes the shift factor along the face width. The end of this section elaborates on five different possibilities to tilt the face cutter head relative to the generating gear, in order to achieve interesting effects on the bevel gear flank form. This installment concludes chapter 2 of the Bevel Gear Technology book that lays the foundation of the following chapters, some of which also will be covered in this series.
  • Development of Usable Bevel Gearset with Length and Profile Crowning (November/December 2015)
    In the previous sections, the development of conjugate bevel gearsets via hand calculations was demonstrated. The goal of this exercise was to encourage the reader to gain a basic understanding of the theory of bevel gears. This knowledge will help gear engineers to better judge bevel gear design and their manufacturing methods. In order to make the basis of this learning experience even more realistic, this chapter will convert a conjugate bevel gearset into a gearset that is suitable in a real-world application. Length and profile crowning will be applied to the conjugate flank surfaces. Just as in the previous chapter, all computations are demonstrated as manual hand calculations. This also shows that bevel gear theory is not as complicated as commonly assumed.
  • Development of a Face Hobbed Spiral Bevel Gearset (September/October 2015)
    This article is the fourth installment in Gear Technology's series of excerpts from Dr. Hermann J. Stadtfeld's book, Gleason Bevel Gear Technology. The first three excerpts can be found in our June, July and August 2015 issues. In the previous chapter, we demonstrated the development of a face-milled spiral bevel gearset. In this section, an analogue face-hobbed bevel gearset is derived.
  • Gear Mathematics for Bevel & Hypoid Gears (August 2015)
    The calculation begins with the computation of the ring gear blank data. The geometrically relevant parameters are shown in Figure 1. The position of the teeth relative to the blank coordinate system of a bevel gear blank is satisfactorily defined with...
  • The Basics of Gear Theory, Part 2 (July 2015)
    The first part of this publication series covered the general basics of involute gearing and applied the generating principle of cylindrical gears analogous to angular gear axis arrangements the kinematic coupling conditions between the two mating members have been postulated in three rules. Entering the world of bevel gears also required to dwell somewhat on the definition of conjugacy. The second part is devoted to the different generating gears and the chain of kinematic relationships between the gear - gear generator - pinion generator and pinion.
  • The Basics of Gear Theory (June 2015)
    Beginning with our June Issue, Gear Technology is pleased to present a series of full-length chapters excerpted from Dr. Hermann J. Stadtfeld’s latest scholarly — yet practical — contribution to the gear industry — Gleason Bevel Gear Technology. Released in March, 2014 the book boasts 365 figures intended to add graphic support of a better understanding and easier recollection of the covered material.
  • Non-Involute Gearing, Function and Manufacturing Compared to Established Gear Designs (January/February 2015)
    Introduction The standard profile form in cylindrical gears is an involute. Involutes are generated with a trapezoidal rack — the basis for easy and production-stable manufacturing (Fig. 1).
  • Less Energy Consumption with High-Efficiency Bevel Gears and their Usage in the U.S. (September/October 2014)
    The efficiency of a gearbox is the output energy divided by the input energy. It depends on a variety of factors. If the complete gearbox assembly in its operating environment is observed, then the following efficiency influencing factors have to be considered
  • Importance of Contact Pattern in Assembly of Bevel vs Cylindrical Gears (August 2014)
    Why is there so much emphasis on the tooth contact pattern for bevel gears in the assembled condition and not so for cylindrical gears, etc?