Convert Degrees to Foot Pounds?

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Working on a Deutz Diesel engine.  The instructions say to torque the
bolts to 30 foot pounds then turn 45 degrees.

Can I convert the degrees to foot pounds so I can use a torque wrench
to make them more exact?

Is there an abbreviation for "foot pounds"?

Re: Convert Degrees to Foot Pounds?
Do what it says.  There are factors that affect torque readings.  The
engineers have it right, no sense second guessing them.


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Re: Convert Degrees to Foot Pounds?
Yep.  It is probably easier to turn 45 degrees and stop rather than to
"torque" to some specified final amount.

Bob Swinney
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Re: Convert Degrees to Foot Pounds?
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    No -- that would be making them *less* exact.

    Do you have an old school protractor?  (The D-shaped thing with
angles marked on it in degrees.)  Use your torque wrench as instructed
to tighten to 30 foot pounds, and then place the protractor to measure
the angle of the wrench handle.  Turn it an extra 45 degrees (1/8 of a
full turn).  This part is to stretch the bolt after you get it to that
torque starting point.  And that bolt should *never* be re-used -- you
stretch it once, no more.

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    "Ft-Lbs" is one.

    Enjoy,
        DoN.

--
    (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
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Re: Convert Degrees to Foot Pounds?

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Doesn't every bolt stretch when you torque it down? How are these
fundamentally different?



Re: Convert Degrees to Foot Pounds?

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Also...
Doesn't this assume that these bolts are tightened past their elastic limit?
Past their UTS?

Surely not...

==
Jeff R.



Re: Convert Degrees to Foot Pounds?


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Brain fart.
I meant "Yield Stress"

(oops)



Re: Convert Degrees to Foot Pounds?

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The tightening technique is to get the bolt very near the yield point,
and not over it. However, if you reuse the bolt, you will exceed the yeld
point.  This will result in insufficient clamping pressure for the joint,
and could (very likely, actually) result in broken fastners.

The torque technique is becoming industry standard nowadays, and that is
because it is inherintly more accurate.
If you torque a bolt to 70-80 lb-ft, the inaccuracies of the measurement
grow expotentially as you increase torque due to friction, head galling,
lubrication distribution and other variables during the tightening.  By
keeping the measured torque lower, you reduce these inaccuracies
substantially. By specifying the angle of final placement from a lower
given torque, you use the thread pitch to determine the linear stretch
amount for the fastener.



--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
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Re: Convert Degrees to Foot Pounds?
vaguely proposed a theory
......and in reply I say!:

  remove ns from my header address to reply via email
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AFAICS, you shouldn't exceed the yield point if you use the bolt
again. The whole idea of Yield point (and I am prepared to learn
another lack in my "knowledge base here, believe me" is that it's the
point at which the steel deforms permanently. Any bolt tightened to
below the yield will return to its former length. (???)

I can see two possible problems. Metal fatigue if the bolt is in place
for an extended time, and / oe under heat/cold/ vibration etc.
Accidental overtightening. Thsi would be an enginerring tning. If the
bolts were _really_ taken to near yield, there would little margin for
error. But once a bolt has exceeded yield, it starts to lose tension
anyway. That woud be dangerous.

Re: Convert Degrees to Foot Pounds?
Old Nick wrote:
 
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Ideally, this is true.  i.e. Yield point is stress level that separates
elastic (returns to original dimention when the stress is relieved) from
plastic (returns to original dimention when the stress is relieved)
deformation.  Regretably most materials do not behave ideally so you
will often see yield point defined as the point where residual
deformation is some small percentage of original dimension.

Ted



Re: Convert Degrees to Foot Pounds?
On Sun, 28 Nov 2004 20:03:17 GMT, Ted Edwards
......and in reply I say!:

  remove ns from my header address to reply via email

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I am sorry. I am a bit confused by the above lines.

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Which is to say that you use a bolt that only _just_ doesn't really do
the job. <G>

Re: Convert Degrees to Foot Pounds?
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The concept behind stress to yield bolts is to get a very consistent
bolt to bolt torque value when tightened according to the listed
procedure. Many modern head bolts have a reduced diameter section
on the shank for this purpose. Torque variance can be as small as
1% using this method. Ordinary torque wrench methods give a
bolt to bolt consistency variance that is often as large as 20%.
Consistent torque reduces the tendency of aluminum heads to
warp.

Gary

Re: Convert Degrees to Foot Pounds?
vaguely proposed a theory
......and in reply I say!:

  remove ns from my header address to reply via email

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AFACUI, the answer is still no if you are asking about stretching. A
spring is the most dramatic example of a metal that can be "stretched"
without exceeding yield stress. To stretch steel you need to apply
stress. It will start to stretch under very small stress. It will
_permanently_ stretch when it passes yield.

Re: Convert Degrees to Foot Pounds?
Jeff R. wrote:
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The Eleventh Commandant:
THOU SHALT NOT ASSUME!
Regards.
Ken.


--
http://www.rupert.net/~solar
Return address supplied by 'spammotel'
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Re: Convert Degrees to Foot Pounds?
DoN. Nichols wrote:
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Precisely!!
Ken.
--
http://www.rupert.net/~solar
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Re: Convert Degrees to Foot Pounds?
On 26 Nov 2004 21:54:28 -0500, dnichols@d-and-d.com (DoN. Nichols)
vaguely proposed a theory
......and in reply I say!:

  remove ns from my header address to reply via email

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Ok. Why should yopu not re-use the bolt? You are only stretching it,
but not to Yield.

I have questioned Anthony about this. My theory says I am right, but
you guys know your stuff. So fact is against me. I am never willing to
let being thought a fool stop me from opening my mouth. I have leraned
a lot that way...

...everything except when to keep my mouth shut! <G>



Re: Convert Degrees to Foot Pounds?

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Metal fatigue plays a factor once the bolt is stretched. I know that there
are a number of engines that use this method in tightening head bolts. And
they are not to be re-used under any circumstances.



Lane





Re: Convert Degrees to Foot Pounds?

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   I think it's because they get hot while under tension and while
getting hammered by the engine.  That gives 'em a small amount of work
hardening that won't like a restretch later on.
   I read it somewhere on the internet, but then again, I read it
somewhere on the internet.

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--
B.B.           --I am not a goat!       thegoat4 at airmail dot net
                                        http://web2.airmail.net/thegoat4 /

Re: Convert Degrees to Foot Pounds?
Recently I borrowed some material from a friend on bolts and read a
lot of it.
And as usual the answer is " it depends ".  Torqueing to a low value
and then tightning a number of degrees was stated as being more
accurate than just using a torque wrench.

But without more information, I can't tell you if these bolts are
being tightned until they yield or not.  You can design bolted joints
so that the bolts are tightened unitl they yield slightly, or you can
design joints so they do not tighten the bolts to yield.

But if the original poster has the book that says how to tighten the
bolts, I am pretty sure it would say if the bolts should not be
reused.  My SWAG would be that tightening them 45 degrees, probably is
not into yield. On the other hand, using new bolts ( of the correct
grade )will never get you into trouble.

                                              Dan


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Re: Convert Degrees to Foot Pounds?

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How can you possibly correlate degrees to Ft lbs ?  If I torque a 1/4 20..
45 degrees that will be much more torque then torque in a 1/4 28... 45
degrees.
If the manual says torque then turn ...it's already calculated on a fresh
bolt ... however if you reuse a standard bolt it has already been stretched
once  ,I would not want to stretch it again.
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