International
and U.S. Gear Standards May Soon Merge
 Bill
Bradley, vice president of the AGMA technical division, discusses how
gear ratings are changing—and how international and U.S. standards
development agencies are working to develop consensus on the subject.
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Q: What are
gear ratings?
There
are a number of standards worldwide for determining the rating or capacity
of gears. And there are different types of gears, so there are standards
for different types. The most common type is referred to as spur and helical
gears, which are gears that are on parallel axes.
Q: Does AGMA
and ISO work together to develop gear ratings?
Yes
and no. The structure is that AGMA is accredited by ANSI as a standards
developing organization. We write national standards. At the same time,
we're also accredited to be the technical advisory group of ANSI that
forms an opinion on international gearing standards. And we do that with
basically the same committees that are forming the national standards.
Q: Does ISO
adopt your standards, or do you have input into the development of its
standards?
Both has happened, but rarely do they adopt them verbatim. The
ones that have been adopted usually have been modified, and that's because
other countries like Germany, France and Japan also have national standards
for gear capacity. ISO has tended to be closer to the German standards
than the U.S. standards.
Q: As AGMA
works on its standards, do you see a growing division between the international
and U.S. standards?
No,
it's the opposite. The goal in the U.S. is to have one internationally
accepted standard. What we're trying to do is either convert to the ISO
standards, modify the ISO standards to be acceptable in the U.S. or have
our standards accepted internationally.
Q: You're
talking about all standards related to gears, not just gear rating standards,
right?
Right. The primary gear rating standard for spur and helical
gears is the most influential. The ISO standard is a series of docs, several
of which were just recently revised and published last year. They have
moved more to the AGMA methods and at the present time we're in committee
on the national standard trying to revise it to look a lot like the most
recent ISO standard. There are still some areas where this ISO edition
and maybe the next U.S. edition will not be the same. Probably the generation
after that they may merge.
Q: How do
companies use the gear rating standards and how do changes in those standards
affect them?
The rating standards are used to determine the capacity or the
amount of power that can be transmitted. If someone buys a gear drive
from a manufacturer, it's more than likely that the purchaser will say
that it is to be designed in accordance with an AGMA or ISO standard.
Using the same standards establishes a common playing field.
Q: So that's
why it would be beneficial to have the same standard?
Correct. That means if somebody in Europe is quoting on the size
of a gear box to do a specific job, somebody in China or Japan or the
U.S. can do the same thing. And they're all doing it to the same standard,
so the purchaser can be assured that everybody is quoting on the same
basis.
Q: Since the
standards aren't the same now, what does that purchaser do now?
Usually they'll ask for the quote either using the AGMA standard,
or DIN, or ISO standard, or one of the other national standards.
Q: It becomes
the manufacturer's responsibility to know the different standards?
Right.
The differences between the standards may determine a different size depending
on the particular application. If somebody specified DIN for certain types
of gearing or a certain range of speed or power, for example, German companies
might have an advantage over U.S. companies.
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