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.
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.
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?
The great thing about a trade show the size of IMTS is the amount of options available to attendees. If you’re into cars, fighter jets, machine tools,
fighting robots, manufacturing relics or
simply the latest technology advancements in a particular industry, you’ll find it at IMTS 2010.
The two-flank roll test measures kickout (tooth-to-tooth composite error) and tooth thickness. In this article, it will be shown that measured values vary with the number of teeth on the master gear.
Dana Corp. is developing a process that carburizes a straight bevel gear to a carbon content of 0.8% in 60 fewer minutes than atmosphere carburizing did with an identical straight bevel.
Bevel gear systems are particularly sensitive to improper assembly. Slight errors in gear positioning can turn a well-designed, quality manufactured gear set into a noisy, prone-to-failure weak link in your application.
This section will deal with the use of gear inspection for diagnostic purposes rather than quality determination. The proper evaluation of various characteristics in the data can be useful for the solution of quality problems. It is important to sort out whether the problem is coming from the machine, tooling and/or cutters, blanks, etc. An article by Robert Moderow in the May/June 1985 issue of Gear Technology is very useful for this purpose.
Quality gear inspection means doing the "right" inspections "right." A lot of time and money can be spent doing the wrong types of inspections related to function and doing them incorrectly. As we will discover later, such things as runout can creep into the manufacturing and inspection process and completely ruin any piece of data that is taken. this is one of the most important problems to control for quality inspection.
The first commandment for gears reads "Gears must have backlash!" When gear teeth are operated without adequate
backlash, any of several problems may occur, some of which may lead to disaster. As the teeth try to force their way through mesh, excessive separating forces are created which
may cause bearing failures. These same forces also produce a wedging action between the teeth with resulting high loads on the teeth. Such loads often lead to pitting and to other failures related to surface fatigue, and in some cases, bending failures.
Your May/June issue contains a
letter from Edward Ubert of Rockwell
International with some serious questions
about specifying and measuring tooth thickness.
Much of the information in this article
has been extracted from an AGMA
Technical Paper, "What Single Flank
Testing Can Do For You", presented in
1984 by the author
With the publishing of various ISO draft standards relating to gear rating procedures, there has been much discussion in technical papers concerning the various load modification factors. One of the most basic of parameters affecting the
rating of gears, namely the endurance limit for either contact or bending stress, has not, however, attracted a great deal of attention.
