Worm Gears

GEAR TALK WITH CHUCK | 2015-02-12

Where is My Flying Car?

It was great fun reading news stories on the Back to the Future anniversary, and which inventions actually happened. Sorry, but a Hover Board jus...

GEAR TALK WITH CHUCK | 2014-01-27

How Did You Become a Gear Expert?

[starbox] Some months ago I got a call from a young engineer asking how he could get into the consulting business. It was a flattering call but a ...

TECHNICAL ARTICLES | 2012-10-01

Pitting Resistance of Worm Gears: Advanced Model for Contact Pattern of Any Size, Position, Flank Type

An experimental and theoretical analysis of worm gear sets with contact patterns of differing sizes, position and flank type for new approaches to calculation of pitting resistance.

ADDENDUM | 2012-03-01

The New Now: U.S. Workforce Sustainability

Faithful Addendum readers are accustomed to finding upbeat, whimsical and oddball stories about gears in this space. What follows is not about gears, exactly. Rather, it is, as opposed to the usual bleak news about America losing its manufacturing mojo—a look at a positive, hopeful development in that regard.

FEATURE ARTICLES | 2011-05-01

Worm Gears - Higher Energy Efficiency and Less Strain on Resources

A very direct and effective way of increasing power transmission efficiency is a changeover from mineral-oil-based lubricants to synthetic lubricants.

TECHNICAL ARTICLES | 2007-08-01

True Bending Stress in Spur Gears

In this paper, an accurate FEM analysis has been done of the “true” stress at tooth root of spur gears in the function of the gear geometry. The obtained results confirm the importance of these differences.

PRODUCT NEWS | 2006-09-01

Product News

The complete Product News section from September/October 2006.

INDUSTRY NEWS | 2005-04-13

Flowserve Introduces New Models to PT Series Worm Gears

Flowserve Corp., a provider of fluid motion and control products and services, added two new sizes to the Flowserve Limitorque PT series ...

TECHNICAL ARTICLES | 2004-07-01

Load Carrying Capacity of Screw Helical Gears with Steel Pinions and Plastic Wheels

There is an increasing significance of screw helical and worm gears that combine use of steel and plastics. This is shown by diverse and continuously rising use in the automotive and household appliance industries. The increasing requirements for such gears can be explained by the advantageous qualities of such a material combination in comparison with that of the traditional steel/bronze pairing.

TECHNICAL ARTICLES | 2003-05-01

Large Scores and Radial Cracks on Case-Hardened Worms

In the last couple of years, many research projects dealt with the determination of load limits of cylindrical worm gears. These projects primarily focused on the load capacity of the worm wheel, whereas the worm was neglected. This contribution presents investigations regarding damages such as large scores and cracks on the flanks of case-hardened worms.

TECHNICAL ARTICLES | 2003-03-01

Determination and Optimization of the Contact Pattern of Worm Gears

The load capacity of worm gears is mainly influenced by the size and the position of the contact pattern.

TECHNICAL ARTICLES | 1999-11-01

Definition and Inspection of Profile and Lead of a Worm Wheel

Traditionally, profile and lead inspections have been indispensable portions of a standard inspection of an involute gear. This also holds true for the worm of a worm gear drive (Ref. 1). But the inspection of the profile and the lead is rarely performed on a worm wheel. One of the main reasons is our inability to make good definitions of these two elements (profile and lead) for the worm wheel. Several researchers have proposed methods for profile and lead inspections of a worm wheel using CNC machines or regular involute and lead inspections of a worm wheel using CNC machines or regular involute measuring machines. Hu and Pennell measured a worm wheel's profile in an "involute" section and the lead on the "pitch" cylinder (Ref. 2). This method is applicable to a convolute helicoid worm drive with a crossing angle of 90 degrees because the wheel profile in one of the offset axial planes is rectilinear. This straight profile generates an involute on the generated worm wheel. Unfortunately, because of the hob oversize, the crossing angle between the hob and the worm wheel always deviates from 90 degrees by the swivel angle. Thus, this method can be implemented only approximately by ignoring the swivel angle. Another shortcoming of this method is that there is only one profile and one lead on each flank. If the scanned points deviated from this curve, it produced unreal profile deviation. Octrue discussed profile inspection using a profile checking machine (Ref. 3).

TECHNICAL ARTICLES | 1999-07-01

Vectors in Gear Design

Friction weighs heavily on loads that the supporting journals of gear trains must withstand. Not only does mesh friction, especially in worm gear drives, affect journal loading, but also the friction within the journal reflects back on the loads required of the mesh itself.

TECHNICAL ARTICLES | 1998-05-01

Relationship Between Wear and Pitting Phenomena in Worm Gears

Worm gears display unique behavior of surfaces because of the presence of wear phenomena in addition to contact pressure phenomena.

TECHNICAL ARTICLES | 1997-09-01

Worm Gear Measurement

Several articles have appeared in this publication in recent years dealing with the principles and ways in which the inspection of gears can be carried out, but these have dealt chiefly with spur, helical and bevel gearing, whereas worm gearing, while sharing certain common features, also requires an emphasis in certain areas that cause it to stand apart. For example, while worm gears transmit motion between nonparallel shafts, as do bevel and hypoid gears, they usually incorporate much higher ratios and are used in applications for which bevel would not be considered, including drives for rotary and indexing tables in machine tools, where close tolerance of positioning and backlash elimination are critical, and in situations where accuracy of pitch and profile are necessary for uniform transmission at speed, such as elevators, turbine governor drives and speed increasers, where worm gears can operate at up to 24,000 rpm.

TECHNICAL ARTICLES | 1997-07-01

Structural Analysis of Teeth With Asymmetrical Profiles

This article illustrates a structural analysis of asymmetrical teeth. This study was carried out because of the impossibility of applying traditional calculations to procedures involved in the specific case. In particular, software for the automatic generation of meshes was devised because existing software does not produce results suitable for the new geometrical model required. Having carried out the structural calculations, a comparative study of the stress fields of symmetrical and asymmetrical teeth was carried out. The structural advantages of the latter type of teeth emerged.

TECHNICAL ARTICLES | 1995-07-01

How to Avoid Errors When Measuring Step Gears

There are problems in dimensional measurement that should be simple to solve with standard measuring procedures, but aren't. In such cases, using accepted practices may result in errors of hundreds of microns without any warning that something is wrong.

INDUSTRY NEWS | 1994-01-01

Cutting Worm Gears with Standard Gear Hobs

We make a lot of single-start worm and worm gear sets, and it always seems as though we're buying another special hob. We also do a lot of spur gear cutting, and the spur gear hobs and the worm gear hobs look alike, so we wonder why we cannot use the standard hobs for cutting worm gears too. Can we do this?

TECHNICAL ARTICLES | 1993-03-01

Introduction to Worm Gearing

Worm gears are among the oldest types of gearing, but that does not mean they are obsolete, antiquated technology. The main reasons for the bad experiences some engineers have with worm gearing are misapplication and misuse. No form of gearing works for every application. Strengths and weaknesses versus the application must be weighed to decide which form of gearing to use. For proper application and operation of worm gears, certain areas that may differ from other types of gearing need to be addressed.

INDUSTRY NEWS | 1992-07-01

Cutting Low-Pitch-Angle Bevel Gears, Worm Gears and The Oil Entry Gap

Question: Do machines exist that are capable of cutting bevel gear teeth on a gear of the following specifications: 14 teeth, 1" circular pitch, 14.5 degrees pressure angle, 4 degrees pitch cone angle, 27.5" cone distance, and an 2.5" face width?

INDUSTRY NEWS | 1992-03-01

Our Experts Discuss Hobbing Ridges, Crooked Gear Teeth, and Crown Shaving

Question: When cutting worm gears with multiple lead stock hobs we find the surface is "ridged". What can be done to eliminate this appearance or is to unavoidable?

INDUSTRY NEWS | 1991-11-01

Gear Inspection Chart Evaluation; Specifying Unusual Worm Gear Sets

Question: When evaluating charts from a gear inspection machine, it is sometimes found that the full length of the profile traces vary, and that sometimes they are less than the length of active profile (above start of active profile-SAP) by up to 20%. This condition could be caused by a concentricity error between tooth grinding and shaping, or by unequal stock removal when grinding. (See Fig. 1.) Is it possible that some of the variation is coming from the inspection machine? How can variation from the inspection machine be reduced?

INDUSTRY NEWS | 1991-07-01

Pineapples, Corncobs & Other Hobbing Matters

Two questions on hobbing cover the various types of hobs and their unusual names, as well as the importance of hob swivel angle.

TECHNICAL ARTICLES | 1990-11-01

Limitations of Worm and Worm Gear Surfaces in Order to Avoid Undercutting

The dimensions of the worm and worm gear tooth surfaces and some of the worm gear drive parameters must be limited in order to avoid gear undercutting and the appearance of the envelope of lines of contact on the worm surface. The author proposes a method for the solution of this problem. The relations between the developed concept and Wildhaber's concept of the limit contact normal are investigated. The results of computations are illustrated with computer graphics.

TECHNICAL ARTICLES | 1988-11-01

Improved Worm Gear Performance with Colloidal Molybdenum Disulfide Containing Lubricants

Worm gear speed reducers give the design engineer considerable options, but these gear systems present a challenge to the lubrication engineer. Heat energy generated by the high rate of sliding and friction in the contact zone causes worm gears to be relatively inefficient compared to other gear types. Because worm gears operate under a boundary or near-boundary lubrication regime, a satisfactory lubricant should contain a friction modifier to alleviate these conditions.

VOICES | 1988-11-01

Viewpoint

Eliot K. Buckingham explains the procedure for proper measurement over wires for worm gears, in response to last issue's article.

TECHNICAL ARTICLES | 1988-03-01

Contact Surface Topology of Worm Gear Teeth

Among the various types of gearing systems available to the gear application engineer is the versatile and unique worm and worm gear set. In the simpler form of a cylindrical worm meshing at 90 degree axis angle with an enveloping worm gear, it is widely used and has become a traditional form of gearing. (See Fig. 1) This is evidenced by the large number of gear shops specializing in or supplying such gear sets in unassembled form or as complete gear boxes. Special designs as well as standardized ratio sets covering wide ratio ranges and center distanced are available with many as stock catalog products.

TECHNICAL ARTICLES | 1987-05-01

Engineering Constants

Rules and Formula for worm gears, bevel gears and strength of gear teeth.

TECHNICAL ARTICLES | 1986-09-01

Gears for Nonparallel Shafts

Transmission of power between nonparallel shafts is inherently more difficult than transmission between parallel shafts, but is justified when it saves space and results in more compact, more balanced designs. Where axial space is limited compared to radial space, angular drives are preferred despite their higher initial cost. For this reason, angular gear motors and worm gear drives are used extensively in preference to parallel shaft drives, particularly where couplings, brakes, and adjustable mountings add to the axial space problem of parallel shaft speed reducers.

TECHNICAL ARTICLES | 1985-01-01

The Effect of Lubricant Traction On Wormgear Efficiency

The effect of various lubricant factors on wormgear efficiency has been evaluated using a variety of gear types and conditions. In particular, the significant efficiency improvements afforded by certain types of synthetic lubricants have been investigated to determine the cause of these improvements. This paper describes broad wormgear testing, both in the laboratory and in service, and describes the extent to which efficiency can be affected by changes in the lubricant; the effects of viscosity, viscosity index improvers and, finally, synthetic lubricants are discussed. The work concludes that lubricant tractional properties can play a significant role in determining gear efficiency characteristics.

TECHNICAL ARTICLES | 1984-10-01

Cone Drive Double Enveloping Worm Gearing Design and Manufacturing

Worm gearing is of great antiquity, going back about 2100 years to Archimedes, who is generally acknowledged as its inventor. Archimedes' concept used an Archimedial spiral to rotate a toothed wheel. Development of the worm gearing principle progressed along conventional lines until about 500 years ago when Leonardo DaVinci evolved the double enveloping gear concept.

VOICES | 1984-08-01

A Second Rate Society - Never

What was once recognized as the unique genius of America is now slipping away from us and, in many areas, is now seen as a "second rate" capability. Unless action is taken now, this country is in real danger of being unable to regain its supremacy in technological development and economic vigor. First Americans must understand the serious implications of the problem; and second, we must dedicate ourselves to national and local actions that will ensure a greater scientific and technological literacy in America.

TECHNICAL ARTICLES | 1984-05-01

CNC Controlled CBN Form Grinding

Borazon is a superabrasive material originally developed by General Electric in 1969. It is a high performance material for machining of high alloy ferrous and super alloy materials. Borazon CBN - Cubic Born Nitride - is manufactured with a high temperature, high pressure process similar to that utilized with man-made diamond. Borazon is, next to diamond, the hardest abrasive known; it is more than twice as hard as aluminum oxide. It has an extremely high thermal strength compared to diamond. It is also much less chemically reactive with iron, cobalt or nickel alloys.