another grease question: bolt threads

I can use a touch of just any old grease to lube bolt threads, right?
E.g. the bolts attaching the slave cylinder to the tranny. Or should I
avoid this so as to lessen the risk of over-tightening them? I do plan
to use a torque wrench. While I'm careful, I sure don't want to run the
risk of stripping out an aluminum block.

 

There's a grease specifically designed to prevent rust around bolt threads. It's
conventionally called "Anti-seize" and has been around for decades in the auto and
many industries that have machinery.

There are a few different grades of "Anti-seize." I buy the grey stuff (which is
perhaps the most frequently used) from Autozone or whoever has the cheapest. Read the
labels and see if it has commentary about temperature applications.

A few bucks for a small tube. A few bucks more will buy you a nice-sized can. Only
takes a little.

Anti-seizing bolts won't mess up the torque you apply.

 

Thanks, Caroline.

 

"Caroline" <> sprach im

Yes it does. Anti-seize and oil both reduce the friction of the threads
against each other. If you use anti-seize, lower your torque wrench setting
10% to compensate for loss of friction.


Copper-based Loctite C5A is better than the aluminum compounds, such as
Permatex 133H.

 

It depends.

1.
If it's an old, somewhat rusted bolt, it may very well noticeably reduce
the friction between male and female threads. And this is for the better.

2.
If it's a brand new bolt, the effects of the lubricant on static friction
are going to be negligible.

Static friction. Go study up on it.

Don't do this. Final, torqued clearance between threads is not affected by
anti-seize.

But may be a waste of money, depending on the particular application.

 

"Caroline" <> sprach im

Static friction is the force you need to overcome when breaking a bolt
loose. It has nothing to do with *dynamic* friction, which is what you
encounter when you tighten a bolt down.

Static friction is why that crank bolt is so hard to get loosened.

Dynamic friction is most definitely affected by lubrication on the threads.
It's the reason why Honda warns against using any lubricant at all on the
threads of the crank bolt.

If you use anti-seize on a bolt, you risk reducing dynamic friction to the
point that your torque wrench will not show a correct reading, and you risk
either overstretching the bolt or stripping the threads, hence the
reduction in torque reading by 10%.

Even that 10% is dependent on how much lubricant you used. Use a small
amount of one kind, and it will make little difference. Use a lot of
another kind and it may reduce dynamic friction by half. As a general rule,
10% reduction is good.

 

i believe you both

 

nope, tegger has it on this one caroline...

 

When one is doing the final torquing of a bolt, static friction has
everything to do with it.

Nope. http://www.honda.co.uk/owner/AccordManual/400/5-36.pdf page 2,
"Apply oil to the bolt threads."

In addition, during operation the crankshaft pulley bolt heats and so
stretches (expanding from the heat), allowing the crankshaft's rotation to
tighten it. Thus after a few years of operation one has the notoriously
tight crankshaft pulley bolt, experiencing torques far in excess of the
torque the technician applies when replacing the belt.

snip

This is an old wives' tale.

You also have to think about
1. precisely where the anti-seize ends up on the bolt's threads
2. what the purpose of anti-seize is.

What surfaces is anti-seize protecting from rust buildup? Not the surfaces
in closest contact.

Now there are applications where anti-seize is specifically prohibited, but
they're rare, and from my reading it's often or always due to a concern
other than overtorquing, such as the stuff chipping off when it's dry and
contaminating something or another.

Lastly, you're omitting the reality that anti-seize overcomes or
compensates for existing rust/detritus on a bolt. To say it somehow 'way
overcompensates' for it (e.g. reducing thread dimensions somehow), is some
kind of wild guess.

Caroline
"20+ years with anti-seize."

 

Ugh. Strike this. I stand corrected on a few important points. Some
reputable sources support Tegger's basic contention. The focus for cars
tends to be (new) spark plug threads, but maybe this is only because this
is where the DIYer is most likely to encounter problems. E.g.

"Most threads on spark plugs designed for aluminum head applications are
precoated to reduce the risk of thread damage. Even so, some technicians
apply a drop of antiseize compound to the plug threads before they go in
for added insurance. General Motors, however, does not recommend this
practice because antiseize acts like a lubricant and may allow the plugs to
be overtightened - which can damage the threads. GM's advice is to reduce
the tightening torque on the plugs 40 percent if antiseize is used on the
threads."

-- Import Car, "Spark Plug Technology Charges Forward," Larry Carley, May
1999

From another source, take two brand new identical bolts. Lube one and keep
the other dry. Torque each to X ft-lbs. Measure the bolt tension. Bolt
tension (= a certain amount of "pull" in pounds on the bolt) is what the
goal is. Torque accomplishes this but indirectly, so to speak.

Dry, the bolt tension will by Y.
With lubricant, the bolt tension is > Y.

Yes, it's due to reduced friction. Call it static or dynamic. It's less.

With an older bolt that is being re-used, I would hesitate to say whether
the prescribed torque should be adjusted. Galling, for one, is likely to be
present, and the lubricant may compensate for this 'just enough.' So I'd
argue (for now), it's a guess as to whether the prescribed torque should be
adjusted.

One may speculate as to why the Honda manual cited above says put a drop of
oil on the crankshaft pulley bolt. E.g.
1. The prescribed torque assumes the bolt has a drop of oil on it.
2. A drop of oil does not significantly affect the tension in the bolt when
torqued to spec.
3. The authors know the bolt will be tightened further by the crankshaft
over time.

Then too I'm not eager to assume prescribed torques (like those in Chiltons
or at the UK site) assume one is not using anti-seize on new bolts. Oxygen
sensor directions say to use a particular antiseize (included with the
sensor in some or all cases). The manuals say then torque to such-and-such.

Sorry Abeness. At this point I can draw only from my own experience: Except
for spark plugs, anti-seize early and often, then torque to spec (without
adjustment).

 

Apologies. Page 6-22 of th'91 Integra manual: Oil on threads, but not bolt
face. I had it backwards.

Still, the presence of oil changes the dynamic friction versus dry,
otherwise why specify?

The same here.

 

Well, I've followed this discussion with interest, and I'm still
confused. It makes perfect sense to my mind that lubrication would
affect the amount of torque to apply, because it reduces friction,
thereby making it easier for the bolt threads to slide on and "pull" the
threads of the hole (and therefore strip them with less torque). I don't
know why a bolt would be any different than a spark plug: they both have
threads, and screw into the engine block--or in this case the tranny
housing.

Where is a mechanical engineer when you need one? I would assume,
perhaps erroneously, that if Honda specified a drop of oil on the
crankshaft pulley bolt but not for other bolts, that the torque
specified for other bolts is that prescribed for non-lubed threads.
Whether that is teh case or not would be anyone's guess. Perhaps I'll
try to contact Honda engineering to inquire.

In the meantime, I suspect I'll do what I usually do in these cases: be
careful, and sensitive to the "feel" of the situation. Truth is, I can
tighten the sucker to a reasonable degree, then check it after a few
days' use and see if it's still tight. If not, I'd tighten it a tad more.

 

They're not. The distinction I was attempting to draw is that this problem
of overtorquing spark plugs arguably is related to the fact that the spark
plug threads are brand new, never been used.

New bolts of any kind will have the same problem, as I'm sure you know,
depending on what is specified re torquing it dry or torquing it with some
kind of lubricant.

Here (to be a total ass), but I flubbed this one. It's not exactly a topic
covered in engineering classes at the undergraduate level. A bit
specialized and more likely something whose detail (e.g. bolt tension) is
more likely to be learned in industry when one is actually required to
design something, liaison with the manufacturers, and then test it. In my
experience. Or that's my pathetic excuse.

Despite my flubbing it, the basic principle (that Tegger first put forth)
should be obvious to most anyone with a bit of hands on experience. A lot
of DIYers talk about the basic idea at their web sites, too. I wasn't
convinced until I came to the comments from GM in the tech article and then
to a site where someone had a lab that could measure bolt tension (not for
the DIYer) and actually did some tests on bolts with and without lube.

Then again, just a few weeks ago torque was discussed in an auto class I
was taking, and while anti-seize was broken out often in the lab, no one
said a word about adjusting the torque to be applied. The instructor was
very competent, too. Maybe he was just a bit rushed.

I recently noticed that Chilton's manuals for many American vehicles like
Fords give a range of torque specs. In Honda manuals, a single value is
given.

This might be related to our discussion.

I suspect dealer and independent shop technicians do the same. Torque
wrenches are rarely broken out. Yet cars get repaired, and only once in a
while does one here of a bolt not properly tightened.

 

And because they have been precoated, acc. to the GM quote, presumably
with a lubricant since the quote goes on to refer to the antiseize
compound as "added insurance". I don't know that other types of new
bolts are precoated. But I really know very little about bolts and
threads...

Mistakes happen, few admit them. No "total asshood" witnessed here. I
should've specified "bolt torque expert". ;-))

Could you post the link? I'd be interested in seeing it myself.

Yeah. I've tightened lots of bolts in my day, never used a torque
wrench, and rarely had a problem. I bought a torque wrench for my Honda
work because the aluminum block makes me nervous (had nice solid
gas-guzzling steel blocks previously)--I expect the "feel" will have to
be relearned for aluminum, so I'll go easy at first.

I also wonder what the "wiggle room" is for the Honda torque specs. As
you note, they specify a single value while others specify a range. How
close to max supported torque are those specs? Probably only a Honda
engineer would know.

 

http://home.att.net/~benmlee/threads/threads.htm

I'm not a fan of reports on personal web sites, but this guy's direct,
hands-on experience (with spacecraft fastener testing) applied to this
little study impressed me.

The valve cover was a big impetus for me to buy a torque wrench.

Otherwise, like you, until recently most of my car work has been without a
torque wrench. Work in industry was a mixed bag. Nuclear: Shucks yes.
Non-nuclear: Time is money.

Have you noticed the front section of many Chilton manuals talks about
torques and gives a table of recommended torque ranges for different sized
bolts as a guideline? Which can be found on the Internet at various sites,
too. E.g. at Autozone for 1984-1995 Civics under "Tools and Equipment":
Bolts marked 6T
6mm bolt/nut: 5-7 ft. lbs.
8mm bolt/nut: 12-17 ft. lbs.
10mm bolt/nut: 23-34 ft. lbs.
12mm bolt/nut: 41-59 ft. lbs.
14mm bolt/nut: 56-76 ft. lbs.

Like you said, the stuff of bolt specialists.

Also, I for one try not to assume too much when I apply bolt specs. After
all, rarely am I working with brand new bolts. What the rust, general
deformation of threads, etc. do to bolt tension for a given torque over
time involves I think consideration of

1. Using antiseize on older bolts that display minor galling.
2. Replacing really old bolts (having worn threads)
3. Torquing to lower end of spec, or possibly reduce the torque spec "some"
amount, when using anti-seize on newer bolts.
4. God knows what temperature changes do to the whole calculation. (Well,
we have some idea: Bolts stretch as they're heated and so tend to loosen.)

 

I wonder why...

I've never paid much attention to bolt torques, for reasons described
previously, so no. I went right to the Helm manual for my Honda, skipped
Chilton's/Haynes entirely after some reports of errors, and I wanted the
full monty.

A wise practice. Thanks for the link.

 

"Caroline" <> sprach im

That's because they tighten until it "feels right". It's learned by
experience.

I do the same with anything I can't get a torque wrench on or if I don't
know what the torque should be.

 

I believe this "experience" of which you speak has no relation to actually
testing the feel of, say, 26 ft-lbs. of torque. Instead, it's "Feels tight.
Must be right." I have a vague recollection of a study that showed what
numerical torque people hoped to achieve and what they actually achieved
were widely different.

One data point: The many anecdotes about lug nuts not torqued to spec, but
to what the operator felt was right, and the warped rotor etc. outcomes of
this.

Sorry, but I had a chance to watch a gaggle of shadetree mechanics
(self-decribed "experts") over the course of several weeks not long ago,
and watching them wrap their ego around their wrong-headedness was
fascinating.

(For the record, I don't find a shadetree mechanic approach here at the
group, for the most part. And yup, I still find the typical, say five years
of experience, shadetree mechanic smarter than an MD. Which is a comment on
doctors... ;-) )

Yup. And I don't lose sleep over it when I do. But this is after years of
experience.

OTOH, who here with 20 years experience with tightening bolts has never
stripped one or sheared off a head? Or had one come loose?

These days when this happens I use the various tables available for
automotive fasteners.

 

Likewise, re the link from Bolt Science (in the other thread you started).
Nice site.

I couldn't resist seeing if there was commentary on how to use the torque
ranges in the Ford Chilton manuals. I checked and couldn't find anything.
But for the record, some examples of ranges from the Chilton manual for
Ford Full Size Vans, 1989-1996:

Wheel lug nuts on 1996 E-250: 126-170 ft-lbs
Shock absorber top mount nut: 25-35 ft-lbs.
Brake caliper mounting bolts: 22-26 ft-lbs.
Exhaust manifold bolts: 18-24 ft-lbs.
Stabilizer bar lock nut: 40-60 ft-lbs.
Oil pan bolts: 9-12 ft lbs.

So for this sample, the specified torque varies from 18% to 50% higher than
the lowest value of toque specified.

Many Chilton manuals also have the following commentary (very much in the
same vein as some of the material at the boltscience.com site):

[Paraphrasing] When tightening a bolt, torque ends up being "distributed"
over three regions:
50% -- overcomes friction between the bolt head and the base surface
40% -- overcomes thread friction
10% -- develops a useful clamp load (which is where bolt tension and the
whole purpose of a bolt come in)

These %s reinforce Tegger's original point: Change the friction between
threads (or head and base) a little, and it will re-distribute a given
applied torque such that bolt tension rises (for better or worse, as the
application indicates).

What to shoot for? To me, the point is that achieving the correct holding
power (a.k.a. clamping force) is a fairly inexact science (which of course
is true of most engineering, depending on how one defines "exact"). One
just can't consistently estimate with much "accuracy" the frictional
resisting force for a given bolt that's been used many times. It's going to
change over time, too, probably. But this should make no one uncomfortable.
Factors of safety make the world go round. Start at the lower end of the
torque range. If the bolt comes loose sooner than expected, increase the
torque.

Also, one's torque wrench may, after years of use, be off by as much as
say, 20%. A big deal? I'd say only with respect to undertorquing.

After all this, I suppose I'd regret my torque wrench purchases of the last
year except that they do ensure uniformity on, for example, lug nut bolts
and valve covers. That's half the battle in ensuring a secure wheel, valve
cover, etc.

 

stripped? yes. big steel bolt, aluminum part

sheared? yes. not uncommon when *removing* siezed fasteners. cant recall
shearing one off while tightening.

loose? only when using worn fasteners, and no loctite, on a buzzy 80cc
scooter engine. i eventually got it right, but the vibration caused
parts of the exhaust to crack, so i learned arc welding as well.

it was either $120 for a new exhaust, or $150 for a small arc welder. i
spent the extra bucks and learned a new skill