Ask the Expert

ASK THE EXPERT | 2020-08-01

Selecting Correct Size of Hob/Gashing Cutter

How does one select the correct size of hob/gashing cutter like hob OD, length and number of flutes for teeth cutting process based on tip circle diameter and face width of job?

ASK THE EXPERT | 2020-03-01

Shaft Positioning Tolerances for Bevel Gears

We know that for cylindrical gears we have the standard DIN 3964 for defining deviations of shaft center distance and shaft position tolerances of casings. And for bevel gears? Is there some specific standard for defining deviations of center distance and shaft position tolerances of casings (orthogonal shafts), as DIN 3964 do?

ASK THE EXPERT | 2020-01-01

Vickers vs. Knoop Hardness Testers for Measuring Case Depth in Carburized Parts

What are the pros and cons of using Vickers versus Knoop hardness testers for measuring case depth in carburized gears?

ASK THE EXPERT | 2019-08-01

Defining the Spline Pressure Angle

A reader requests help designing the mating gear for an internal spline.

ASK THE EXPERT | 2019-07-01

Tooth Thickness Tolerance and AGMA 2002-C16

A reader asks: We are currently revising our gear standards and tolerances and a few questions with the new standard AGMA 2002-C16 have risen. Firstly, the way to calculate the tooth thickness tolerance seems to need a "manufacturing profile shift coefficient" that isn't specified in the standard; neither is another standard referred to for this coefficient. This tolerance on tooth thickness is needed later to calculate the span width as well as the pin diameter. Furthermore, there seems to be no tolerancing on the major and minor diameters of a gear.

ASK THE EXPERT | 2019-05-01

Application Factors

A reader asks: I'd like to know about the different approaches and factors considered while determining the value of Ka in regards to the DIN 3990 and AGMA standards.

ASK THE EXPERT | 2019-03-01

Relationship between Misalignment and Transmission Error in Cross- Axes Helical Gear Assemblies

Question: I am a gear engineer for a motor manufacturer in China. I am writing about noise generated from cross-helical gear assembly error. I want to learn the relationship between the misalignment (center distance change and cross-angle shift) and transmission error. It is better under the loading and theory conditions. What is the trend of cross-helical gear development (use ZI worm and involute helical gear, point contact)?

ASK THE EXPERT | 2019-01-01

State of the Gear Industry Special Edition

Gear industry experts give their opinions about the most important trends facing gear manufacturers today.

ASK THE EXPERT | 2018-09-01

Lubrication: Viscosity and Macropitting

A reader asks: Is the ISO VG 320 adequate, or should a higher viscosity grade be used? How can we stop macropitting in gear teeth?

ASK THE EXPERT | 2018-06-01

Selecting the Right Tooth Thickness

A reader asks: We are currently revising our gear standards and tolerances, and a few problems with the new standard AGMA 2002-C16 have arisen. Firstly, the way to calculate the tooth thickness tolerance seems to need a "manufacturing profile shift coefficient" that isn't specified in the standard; neither is another standard referred to for this coefficient. This tolerance on tooth thickness is needed later to calculate the span width as well as the pin diameter. Furthermore, there seems to be no tolerancing on the major and minor diameters of a gear.

ASK THE EXPERT | 2018-05-01

Calculated Gear Life Values

I have a query (regarding) calculated gear life values. I would like to understand for what % of gear failures the calculated life is valid? Is it 1-in-100 (1% failure, 99% reliability) or 1-in-one-thousand (0.1% failure)?

VIDEO | 2017-12-01

Ask the Expert Live 2017 - Cylindrical Gear Cutting

Gear Technology's panel of experts answer your questions about hobbing, shaping, power skiving and more at Gear Expo 2017. Featuring Dr. Hartmuth Mueller of Klingelnberg, Dr. Hermann Stadtfeld of Gleason, Dr. Oliver Winkel of Liebherr and Tom Ware of Star-SU.
 

VIDEO | 2017-12-01

Ask the Expert Live 2017 - Gear Inspection

Gear Technology's panel of experts anwer your questions about Gear Inspection. Featuring Mariano Marks of Wenzel America, Dr. Hartmuth Mueller of Klingelnberg and Bill Miller of Kapp-Niles. Recorded at Gear Expo 2017 in Columbus, OH.

VIDEO | 2017-12-01

Ask the Expert Live 2017 - Ask Anything

Gear Technology's panel of experts answer your questions about gear design, manufacturing, inspection, heat treating and more during this session of Ask the Expert Live! Featuring Michael Hein, team leader at the FZG gear research center; Dr. Ulrich Kissling, President of KISSsoft AG, Dr. Hermann J. Stadtfeld, VP Bevel Gear Technology and R&D at Gleason, and Gear Technology technical editors Octave Labath and Chuck Schultz. Recorded October 25, 2017 at Gear Expo 2017 in Columbus, OH.

ASK THE EXPERT | 2017-11-01

Friction Coefficient of Differently Treated Steel Surfaces

A reader asks about ion-nitride finished shafts and the proper friction coefficient to be used for calculations.

ASK THE EXPERT | 2017-09-01

Backlash and Axial Movement

What is the relationship between angular backlash and mean or normal backlash, the axial movement of wheel gear, and mean or normal backlash for bevel and hypoid gears?

ASK THE EXPERT | 2017-07-01

Backlash in Bevel and Hypoid Gears

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?

ASK THE EXPERT | 2017-06-01

Ground and Hobbed Globoidal Worm Sets

A reader wants to know: Are profile ground and hobbed globoidal worm sets better than multi-axis CNC generated globoidal worm gear sets for reduction of noise and vibration?

ASK THE EXPERT | 2017-05-01

Gear Teeth as Bearing Surfaces

A reader wonders about gears where the tops of the teeth are the bearing surface, as used in spur gear differentials. Do they require any special construction or processing?

ASK THE EXPERT | 2017-03-01

Universal Hobs

Another expert takes a crack at a previously answered question about double-helical gears and universal hobs.

ASK THE EXPERT | 2017-01-01

Best Tooling for Hard Milling a Gear Tooth on 5-Axis Machining Center

What is the best tooling to use when hard milling a gear tooth on a 5-axis machining center? And what makes it the best? We have just bought a DMG Mori mono-block and are not getting the finishes at the cycle times we require.

ASK THE EXPERT | 2016-11-01

Locating Multiple Bore Diameters Via Hobbing

Attached photos (Figs. 1-2) show a bushing to locate one single bore. This will be used to locate one single bore diameter of a gear wheel. What is (the latest) technology for common clamping a bushing to locate multiple bore diameters in hobbing?

ASK THE EXPERT | 2016-09-01

Same Hob for Two Gears

I make all the double helical gears that go into a gearbox - four different gears in this unit. If the gear module for the bull gear and the intermediate gear are the same (these are the two individual gears that mate), and the gear module for the high-speed pinion and high-speed gears are the same (these are the other two individual gears that mate in the gear box as well), is it then possible to just use two hobs in this setup to make all four gears, since they mate together with each other? We are currently using a different gear hob for each gear.

ASK THE EXPERT | 2016-08-01

Helical Gear Systems

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?

ASK THE EXPERT | 2016-05-01

Idler Gears

What is the point of using two idler gears in a geartrain?

ASK THE EXPERT | 2016-03-01

Hard-Finishing Spiral Bevel Gears

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?

ASK THE EXPERT | 2016-01-01

Premature Gear Failure

I would appreciate if you could assist with a gear failure (occurring) after just seven weeks in service, post installation. This driving gear wheel has been installed in a medium-speed engine with backlash present at four different positions; with additional backlash checked on the mating surfaces. All backlash was found within (OEM)-recommended values. Please note included photos - it seems that the crack has started at the root fillet. Any comments would be appreciated.

VIDEO | 2015-11-18

Ask the Expert - Cutting Tools

ASK THE EXPERT LIVE took place at Cobo Hall in Detroit Michigan on October 20th and 21st, 2015

The Cutting Tools segment took place on October 20th at 2:00 p.m.

Total playback time 39:51

The Following is the list of experts for this session

CUTTING TOOLS — Tuesday, 10/20 — 2:00 p.m.

• Dr.-Ing. Nicklas Bylund, Sandvik Coromant, Manager Engineering Competence Center
• Dr. Hermann J. Stadtfeld, Gleason Corporation, VP Bevel Gear Technology/R&D
• John O'Neil, Engineering Manager for Gear Cutting Tools, Star SU

We have an ASK the Expert almost every issue. If you are not already a subscriber, please take the time to subscribe to digital and/or print. Subscribe Here

VIDEO | 2015-11-18

Ask the Expert Live - Ask Anything

ASK THE EXPERT LIVE took place at Cobo Hall in Detroit Michigan on October 20th and 21st, 2015

The Ask Anything segment took place on October 21st at 2:00 p.m.

Total playback time 54:02

The Following is the list of experts for this session

Ask Anything - Wednesday, 10/21 - 2:00 p.m.

• Prof. Dr.-Ing. Karsten Stahl, Technical University of Munich, Head of the Gear Research Center (FZG)
• Dr. Hartmuth Müller, Klingelnberg, Chief Technical Officer
• Chuck Schultz, Principal, Beyta Gear Service
• Octave Labath, Gear Technololgy Technical Editor

We have an ASK the Expert almost every issue. If you are not already a subscriber, please take the time to subscribe to digital and/or print. Subscribe Here

VIDEO | 2015-11-18

Ask the Expert - Gear Grinding

ASK THE EXPERT LIVE took place at Cobo Hall in Detroit Michigan on October 20th and 21st, 2015

The Gear Grinding segment took place on October 20th at 10:30am.

Total playback time 1hr 1min

The Following is the list of experts for this session

Gear Grinding - Tuesday, 10/20 - 10:30a.m.

• Dr. Hermann J. Stadtfeld, Gleason Corporation, VP Bevel Gear Technology/R&D
• Dr.-Ing Andreas Mehr, Liebherr, Technology Development, Grinding and Shaping
• Enrico Landi, Machine Tools Product Center Director, Samputensili, Star-SU
• Harald Gehlen, Head of Application Engineering, Reishauer

We have an ASK the Expert almost every issue. If you are not already a subscriber, please take the time to subscribe to digital and/or print. Subscribe Here

ASK THE EXPERT | 2015-09-01

Liebherr - Barber Colman Hob Settings

I would like some instructions for setting the degrees and minutes on a Liebherr or Barber Colman hob. Our machines use a Vernier scale to match the lead angle of the cutter to the part to form straight teeth. There is a dispute on how to do this task, and I wanted insight from another professional.

ASK THE EXPERT | 2015-09-01

Gear Macrogeometry

I have outsourced gear macrogeometry due to lack of resources. Now I received the output from them and one of the gears is with —0.8× module correction factor for m = 1.8 mm gear. Since bending root stress and specific slide is at par with specification, but negative correction factor —0.8× module — is quite high — how will it influence NVH behavior/transmission error? SAP and TIF are very close to 0.05 mm; how will that influence the manufacturing/cost?

ASK THE EXPERT | 2015-07-01

Determining Bull Gear Wear

We are currently experiencing wear on the bull gear on our converter at the steel plant. We want to be able to draw the original gear profile to compare this with the worn tooth before we decide on the next steps. I have attempted this, but there is a correction factor given and I am unsure how to apply this. Could someone give advice on this? Please find attached the PDF’s for the bull gear and the pinion gear. They are old drawings! The wear is on the wheel.

ASK THE EXPERT | 2015-06-01

Gear mesh, NVH Evaluation

The question is quite broad, as there are different methods for setting various types of gears and complexity of gear assemblies, but all gears have a few things in common.

ASK THE EXPERT | 2015-05-01

Gear Mesh Assembly

When assembling a pair of gears, what is a good method for setting and checking their mesh?

ASK THE EXPERT | 2015-03-01

Calculating Face Load Distribution Factor

How should we consider random helix angle errors fHβ and housing machining errors when calculating KHβ? What is a reasonable approach?

ASK THE EXPERT | 2015-03-01

Measuring Residual Stress in Gears

I have heard that X-ray diffraction does not tell the whole story and that I should really run a fatigue test. I understand this may be the best way, but is there another method that gives a high degree of confidence in the residual stress measurement?

ASK THE EXPERT | 2014-11-01

Small-Module Gear Design

Gears with a diametral pitch 20 and greater, or a module 1.25 millimeters and lower, are called fine-pitch or low-module gears. The design of these gears has its own specifics.

ASK THE EXPERT | 2014-09-01

Lubrication Lexicon

I must confess I sometimes find myself a bit dazed when discussing lubrication issues with either staff or vendors. The terminology seems to be all over the lot, with some terms having double meanings. Can you help cut through the confusion?

ASK THE EXPERT | 2014-08-01

Importance of Contact Pattern in Assembly of Bevel vs Cylindrical Gears

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?

ASK THE EXPERT | 2014-08-01

Additives: Anti-Wear vs Anti-Scuff

A reader asks: While I have read a reasonable amount of the literature on the pros and cons of anti-wear and anti-scuff additives, I find that the more I read, the more confused I become. I could use some clarity in my life.

ASK THE EXPERT | 2014-08-01

The Pros and Cons of Fully Ground Root Fillets

For maximum life in carburized and ground gearing, I have been advised that fully grinding a radius into the root gives maximum resistance against fatigue failures. Others have advised that a hobbed and unground radius root form is best. Which is best, and why?

ASK THE EXPERT | 2014-07-01

Deciding When to Go Plastic

Can my metal gear(s) be replaced with plastic gears?

ASK THE EXPERT | 2014-06-01

Measuring Backlash in Bevel and Hypoid Gears

In this installment of Ask the Expert, Dr. Stadtfeld describes the best methods for measuring backlash in bevel gears.

ASK THE EXPERT | 2014-01-01

Planet Carrier Design

With all the advantages of building float into a planetary gear system, what advantages are there to using a carrier in the first place, rather than simply having your planets float in the system?

ASK THE EXPERT | 2013-11-01

High Temperature Gear Materials

What gear material is suitable for high-temperature (350 – 550 degree C), high-vacuum, clean-environment use?

ASK THE EXPERT | 2013-10-01

Worm Gears - Ask the Expert

How does one determine the center of a worm and a worm wheel? Also, what are the differences between the common worm tooth forms?

ASK THE EXPERT | 2013-09-01

Lubrication Specification and Methodology

A reader asks about how to specify a method of lubrication for a speed reducer with a three-stage helical gear with a low peripheral speed.

ASK THE EXPERT | 2013-08-01

Girth Gear Inspection - Pre- and Post-Manufacture

What are the ins-and-outs of quality inspection of girth gears, from both a manufacturer and buyer perspective? Our experts respond.

ASK THE EXPERT | 2013-06-01

Worn Gear Contact Analysis

How does one perform a contact analysis for worn gears? Our expert responds.

ASK THE EXPERT | 2013-03-01

Workholding Options

Question: We manufacture some gears that require an axial face as a datum, as well as locating on the bore for centering. Other gears use only the bore for both axial and radial locating. What type of workholding is appropriate for each type of part? Is there workholding that will work for both types?

ASK THE EXPERT | 2013-01-01

Measurement of Involute Master

Our experts tackle the topic of measuring involute masters, including both master gears and gear inspection artifacts.

ASK THE EXPERT | 2012-11-01

Gleason Machine Setup

A reader asks about the proper setup procedures for cutting a ring and pinion set on a Gleason 116.