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From: John De Armond
Subject: Re: Torqued Yer Hitch Bolts Lately?
Date: Fri, 29 Oct 1999 03:41:39 EDT
Newsgroups: rec.outdoors.rv-travel

"E. Myers" wrote:
> On our last long trip I started noticing a "push-pull" type feeling whenever
> I stopped.  After parking I got to inspecting the system and found the ball
> nut had come loose on the hitch even though it had a lock washer on it.
> Arriving home I replaced the ball and the shaft was worn probably 20%
> through. I carry a 16" crescent just to tighten that nut but had failed to
> keep an eye on it.  Won't miss it again!
> Ed

Seeing all these tales about loose fasteners, I thought I'd mention
something that's like a 3rd hand to a race mechanic - Loctite.  This
is a specialized single component adhesive that cures in the absence
of air (anaerobic) and is applied to fasteners (bolts, nuts, screws,
etc) to lock the threads.  Only the part actually within the threads
and thus deprived of air hardens.  The rest remains liquid and can
be wiped away after assembly.  Loctite comes in grades that are
color coded.  Blue is ordinary strength and provides about the same
locking action as a star washer.  The fastener can easily be
loosened with hand tools.  Red is the next step up.  It is quite
strong and requires considerable force to break loose but can be
removed with hand tools without heat.  This is the grade I use for
all types of fasteners with a shank diameter equal to or smaller
than 3/4".  Larger fasteners are adequately locked with blue; red
may be impossible to remove without heat on the larger fasteners. 
Green is the strongest.  It normally cannot be broken loose with
hand tools.  An air impact wrench will break free smaller
fasteners.  Larger ones must be heated.  I use green in high stress,
high vibration areas such as suspension fasteners.  Green is also
known as bearing and bushing lock because it can be used to lock a
loose bearing in its housing and to secure bushings.

I use the brand name Loctite because I have found that brand to be
far superior to competing brands.

Another technique used in the racing field that was adopted from the
aviation world is drilling fasteners for safety wire.  I drill and
safety wire any fastener whose failure would cause a hazardous
condition (single point failure.)  Trailer hitch bolts fall in this
category.  Pre-drilled aerospace-grade fasteners (AN- designation,
180,000 psi yield strength) can be had surprisingly inexpensively
from companies like Alexander Aeroplane (800 831-2949) in Atlanta
who cater to the experimental/home built airplane market.  Racing
supply companies such as JEGS and Summit Racing sell jigs that make
drilling fasteners very easy.  All the above companies sell safety
wire pliers that make applying safety wire very simple.  These
pliers contain a leadscrew in the handle that, when pulled, twists
the wire to the proper tightness.  American-made pliers cost about
$60.  Chinese clones go for about $15-20.

One other thing I might mention.  Standard (non-metric) bolts are
graded according to strength.  The system ranges from Grade 2
(cheap, weak) to Grade 8 (about 90,000 psi yield strength, if my
memory serves). The caps of the bolts are marked with radial slashes
that designate the grade.  There are 2 less slashes than the grade
number.  In other words, a Grade 8 bolt will have 6 slashes; a grade
5 will have 3 slashes.  When I had a Class III hitch mounted to my
catering Step-Van, I noticed that the (formerly) reputable hitch
shop used Grade 2 bolts to attach the hitch to the chassis.  This
was unacceptable to me.  Before using the hitch, I replaced the
fasteners with Grade 8 bolts.  These Loctited bolts have never
required retorquing and have never loosened.  I suspect that these
cases where fasteners are repeatedly loosening and requiring
retorquing are overloaded and are stretching.  Replacing the
fasteners with Grade 8 bolts should solve the problem.  

From: John De Armond
X-Source: The Hotrod Mailing list
Date: May 1994
Subject: clearance for Locktite?
X-Sequence: 8538

Found this on the net.  Thought it might come in handy.


Greg Lewis (gregl@zimmer.CSUFresno.EDU) wrote:
: How much clearance should one allow for a cylindrical shaft and hole
: set with Loctite?...

... and how long is that piece of string anyway? :)

How much you can get away with depends on which particular flavor of Loctite
you're using. Optimally, the gap should be between 1 and two thou all the
way around. Incapable of leaving it at that, however, I'll throw in the table
from the current Loctite catalog on the end of this posting.

Yes, I know it's overkill but someone else might find it useful. It's not
readily available unless you call Loctite for the data sheets or go find a
supplier with some spare catalogs.

Tim Kirby --------- Cray Research Inc., Eagan, MN, USA ----------
Disclaimer: Cray didn't say this... I did...
If all else fails, Immortality may always be assured by spectacular error(JKG)

Loctite Retaining Compounds

+ The gap fills are all *maximum*. According to the guy at Loctite when I
  asked these very questions some time ago, the optimum gap is between 0.001"
  and 0.002" (0.002 to 0.004 diametral) for any of theses adhesives.
+ This table refers to the *retaining compunds*, not *threadlock compunds*
+ The viscosity "Low/Med./High" is from the descriptions for each product
+ The '660' is referred to as 'Quick Metal', considered a non-running product
+ If you're using another brand (is there any other ? :) you're on your own.
+ Cure Speed assumes no accelerator is used. Activators/accelerators may
  improve the gap filling capabilities slightly as well as ensuring proper/
  faster curing respectively. If you need to accelerate it, talk to your
  dealer; I don't have any specific numbers.
+ Primers are useful on inactive surfaces such as aluminum, black oxide,
  stainless steel and thermoset plastics
+ Remember... *CLEAN CLEAN CLEAN* !!!

Compound  No.     609    620    635    640    642    660     675    680

Color            Green  Green  Green  Green  Green  Silver  Green  Green

Gap Fill         0.005" 0.015" 0.010" 0.007" 0.012" 0.020"  0.005" 0.015"

Viscosity        V.Low  High   High   Med.   Med.   !!!!    Low    Med.
  (cP)            125   7000   2000   600    500   1200000  125    1250

Shear (psi)      3000   3000   4000   3000   3500   3000    3000   4000

Temp Range(F)

   Low           -65    -65    -65    -65    -65    -65     -65    -65
   High          300    450    300    400    350    300     300    300

Cure Speed

 Fixture (Min)   10     30     60     60     5      10      20     10
   Full  (Hrs)   24     24     24     24     24     24      24     24

Primer         T or N   T      T      T   T or N    N       T      T


609: spindle bearings, lip seals, bearing races

620: engine cylinder liners, heat exchanger tubes

635: gears, pulleys, fans, collars, rotors, sprockets, cams and flywheels
           to shafts.

640: bushings and sleeves, rotors to shafts

642: bushings in manual transmissions

660: worn shafts, worn housings, worn end bells, bearing spinouts,
           wallowed keyways, wallowed splines

675: oil impregnated bushings, drill bushings

680: gears, wheels, pulleys, cams, collars, flywheels, sprockets, and rotors
           to shafts, replacement bearings in worn housings or on worn shafts.

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