Convert Degrees to Foot Pounds?



I don't think I said anything about correlating degrees to ft lbs. But if you have say a 4 inch long 1/4 20 bolt and you tighten it so it is snug and then tighten it 45 degrees, you will have stretched the bolt 0.0125 inches. So for a 4 inch long bolt you would have stretched it .0031 inches per inch of length. Now assuming this is less than yield, you can loosen it and retighten it over and over. No new bolt needed. You don't worry about flexing the springs in your car, do you. Stretching less than yield means it returns to the original length when the stress is removed.
If you use a different length bolt, or a bolt with different threads per inch, you have to calculate how many degrees to tighten it for the stain you want.
Dan
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    *You* didn't -- but it is in the "Subject: " header from the original question.

    And to calculate the equivalent foot-pounds figure, you would need to know the diameter of the section being stretched, the length of the reduced diameter or section being stretched, and the tensile strength at the current temper of the material. (And, as has already been discussed, trying to do it all with a torque wrench is less accurate.

    *Or* -- a different reduced diameter length, if present. And that would be more likely to be a torque to yield bolt application.
    Enjoy,         DoN.
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wrote in message news:<Bhtqd.2617$

> I don't think I said anything about correlating degrees to ft lbs.
The name of the thread is convert degrees to Foot Pounds so I assumed that's what the subject was ... happens all the time where a thread starts out one thing and turns into something else. I guess you have to go back to the original post to figure out where the subjects at ... I don't because some of the threads are really long.

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On 30 Nov 2004 19:29:53 -0800, snipped-for-privacy@krl.org (Dan Caster) vaguely proposed a theory ......and in reply I say!:
remove ns from my header address to reply via email

This was my argument. But it would seem that in the real world, that stretched bolt has been "damaged", or is assumed to be damaged. Minimalism in engineering, heat, vibration etc.
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replying to Dan Caster, Tom wrote: How about if I'm using my old head bolt it's a nissan altima 2.5 liter it only give me a 35 foot pounds then add 75 to 80 degrees
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On Mon, 19 Dec 2016 18:18:02 +0000, Tom

Called torque to yield - AKA big expense as they are not to be re-used - and they are not cheap. Also called "stretch bolts"
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wrote:

http://www.felpro-only.com/blog/proper-installation-use-t-t-y-bolts/
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On Monday, December 19, 2016 at 5:15:43 PM UTC-5, Jim Wilkins wrote:

FWIW, the explanation on that site is not quite right. A bolt, or any piece of steel that has even a small amount of ductility, will continue to devel op more stress (clamping force) well after its yield point is reached. It i sn't practical to use that part of the curve for something like a head bolt for a couple of reasons, one of which is that different grades of steel ca n behave very differently after you pass the yield point.
What you get, with TTY bolts, is a reliably accurate and consistent clampin g force, combined with a small amount of elasticity that will keep the clam ping force very high even if the strain is somewhat relaxed, as when an eng ine cools down a bit after running hot.
But you can, as a technical issue, increase the clamping force by torquing beyond the yield point. It just isn't a practical thing to do in ordinary c ircumstances with normal bolts or studs.
--
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wrote:

FWIW, the explanation on that site is not quite right. A bolt, or any piece of steel that has even a small amount of ductility, will continue to develop more stress (clamping force) well after its yield point is reached. It isn't practical to use that part of the curve for something like a head bolt for a couple of reasons, one of which is that different grades of steel can behave very differently after you pass the yield point.
What you get, with TTY bolts, is a reliably accurate and consistent clamping force, combined with a small amount of elasticity that will keep the clamping force very high even if the strain is somewhat relaxed, as when an engine cools down a bit after running hot.
But you can, as a technical issue, increase the clamping force by torquing beyond the yield point. It just isn't a practical thing to do in ordinary circumstances with normal bolts or studs.
--
Ed Huntress

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On Monday, December 19, 2016 at 9:58:21 PM UTC-5, Jim Wilkins wrote:

Right. Depending on the alloy and the state of heat-treatment, most steels can be stressed quite a bit higher than the yield point, and they display more strength.
By that time, though, your threads commonly are going to hell. d8-)
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wrote:

The head bolts for my 1978 Honda Accord were so exotic looking that I bought one to study. The shank was necked down smaller than the threads and deeply roll-indented in a coarse spiral pattern, which I think was to selectively work-harden the shank where it stretched while the thicker threaded end didn't stretch enough to progressively strip the threads in the block.
-jsw
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On Tuesday, December 20, 2016 at 1:39:55 PM UTC-5, Jim Wilkins wrote:

Wow, that's pretty fancy. I've never seen those.
At Wasino, we turned test runs of big-end bolts for Cosworth engines. They were a bitch; we had to use custom PCBN inserts to turn the threads.
Anyway, they had a *much* thinner shank, possibly because the threads were a weak point. The more accurate way to describe it may be that the threaded portion was intentionally oversize.
--
Ed Huntress

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On Mon, 19 Dec 2016 18:34:01 -0800, edhuntress2 wrote:

Reuben Geissler, my across-the-road neighbor, when I was 14, advised me that the way to find the correct torque on my 1948 Chevy head bolts was to "torque them 'till they break, then back off half a turn". I see no reason why that advise isn't just as valid today as it was then.
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Tim Wescott
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wrote:

I've always -loved- that one. LOL! "Tighten it until it snaps, then _quickly_ back if off half a turn."
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On 19/12/16 21:57, snipped-for-privacy@snyder.on.ca wrote:

IIRC it depends on the design and what the makers say. The Rover K series engine uses torque angle method and the bolts can be re-used a few times provided the overall length doesn't exceed a specified length, the design does use long bolts though that run from the top of the engine through to the bottom ladder assembly which supports the crankshaft. Price can be cheap I recall the FIAT twin cam used torque to yield head bolts but they were quite cheap to get a set of them even from the main dealer.
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wrote:

The vast majority of TTY boltsm I encountered up untill about the early nineties were single use bolts according to the factory manuals at the time.
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On Mon, 19 Dec 2016 20:46:16 -0500, snipped-for-privacy@snyder.on.ca wrote:

What do you give the odds of the replacements being installed correctly or the originals being reused? I've never seen TTY bolts, but I got out of the biz in '85. It's been a while.
I have, however, seen plenty of people who used a torque wrench improperly, trying to speed up the act of torquing bolts down. It _always_ resulted in too little torque being applied to the head- or main-bolts, sometimes with disastrous results.
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On Tue, 20 Dec 2016 12:22:21 -0800, Larry Jaques

The only time I tried to re-use TTY headbolts I had to replace them a few months later and it cost me a head gasket. When they break, you can'y easily remove them without pulling the head. They may have been compromised by not being properly torqued before, Undertorqued, they fatigue from stretching and relaxing with every heaty cycle. Properly totqued they basically don't move.
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On Tue, 20 Dec 2016 20:19:31 -0500, snipped-for-privacy@snyder.on.ca wrote: I said:

Ooh, bummer. Did you not know about their being TTY? Total cost was a set of bolts, another head gasket, and another gasket job. Both time- consuming and costly, right? Ouch.

UTI was a long time ago, but I don't recall ever hearing that an undertorqued bolt fatigued from stretching like that. I may never have learned about it.
Volkswagons are the leader when it comes to massive stretching of the head bolts. I've heard them going down the street, the heads bopping up and down on the cylinders. It heightens my disdain for the ugly, hissing beasties. The Cherman engineers should be shot for the noise + harmonics the engine and muffler produce. Give me fingernails on a chalkboard any day, over that monstrosity. Thankfully, the new Bug engines are all but silent.
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wrote:

I bought two $300 high-mileage Beetles which were pretty quiet after I adjusted the valves.
This morning I addressed two other issues that might be of interest. I bought a used 120VAC starter to fit the Tecumseh HSK70 engine on my 20-year-old Toro 724 snowthrower. Running a 1/4-20 bottoming tap into the mounting holes in the block cut two more turns and let them accept 1/2" long screws. I've seen the shallow holes strip, possibly from using 3/8" screws.
I use Dell D820 laptops running Win7 as portable TVs and digital recorders. On one the screen started intermittently blanking which turned out to be triggered by the lid-closed switch, a magnet in the lid by the latch and sensor in front of the right touchscreen button. You can find the magnet with a paper clip. Holding a magnet over the sensor blanks the screen even if Do Nothing is set in Power Options. Apparently this is an APCI Lid driver bug in Vista, Win7 and maybe 10. The suggested fix is to replace (disable) it with the Volume Manager driver, which seems to work so far. Swiping a magnet over the sensor to simulate closing the lid still blanks the screen. http://www.techsupportforum.com/forums/f217/solved-laptop-lid-problem-164329.html
--jsw
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