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From time to time, we get complaints from customers regarding galling of stainless steel fasteners.
Here is an excerpt from the Industrial Fastener Institute's Standards Book:
Thread galling seems to be
the most prevalent with fasteners made of stainless steel, aluminum, titanium and other alloys which
self-generate an oxide surface film for corrosion protection. During fastener tightening, as pressure
builds between the contacting and sliding thread surfaces, protective oxides are broken, possibly wiped
off and interface metal high points shear or lock together. This cumulative clogging-shearing-locking
action causes increasing adhesion. In the extreme, galling leads to seizing - the actual freezing together
of the threads. If tightening is continued, the fastener can be twisted off or its threads ripped out.
During minor galling, the fastener can still be removed, but in severe cases of galling, a strong bond
between the bolt and nut can prevent removal of fasteners. Unfortunately, little is known on how to
control it, but here are two ways to minimize this effect:
Decreasing installation RPM speed will cause
less friction and decrease heat generation.
Lubrication used prior to assembly can dramatically reduce
or eliminate galling. Recommended lubricants should contain higher amounts of molybdenum disulfide,
such as graphite which is very commonly used as a solid lubricant or special anti-galling lubricants sold
by chemical companies.
We provide an anti-seize compound stick called “Thread Magic” with all of our antennas and strongly
encourage you to use it to reduce the aggravation of galling. Nylock nuts are no exception—apply the
anti-seize on fastemers that use Nylock nuts as well. The Thread Magic stick is fantastic and is good
for all metal fastener use—and, you can get plenty of anti-seize on the fastener without getting it on
your hands!
Turn-of-nut tightening of nuts to bolts is recommended where torque values are not named, with metal
to metal connections. Turn the wrench/socket until it is flush with the material it will seat against and
snug-tightened, and then turn approximately 2/3 of a rotation past that point. When in doubt use com-
mon sense to ensure the fastener is not too loose, or not too tight—both positions can cause issues.
On all connections, check the tightness 30 minutes or more later to ensure no creeping has taken ef-
fect.
Contrary to popular belief, galling of stainless steel is not a symptom of a "cheap" fastener - it is preva-
lent in all types of stainless steel, aluminum and titanium fasteners. You can be assured that the stain-
less steel fasteners we provide with our products are manufactured of very high quality.
Save yourself a lot of grief and always use a thread lubricant when working with stainless
steel fasteners.
STAINLESS STEEL FASTENER INFORMATION
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