Convert Degrees to Foot Pounds?

_Torque_ or energy

Not up on modern engines are you ? Head bolts on almost everything out there now has a torquing sequence where the last step is to turn the bolt a specified number of degrees . It's called "stretch to torque" . Even my antique (officially ! it's a 1990) Harley has that type of cylinder studs .

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Snag

Do they ever stop stretching on that paintshaker?

How dare you ! Actually , mine is a touring bike with a rubber mounted motor/trans/swing arm assembly . Rides quite smoothly ... mine's not stock , I've fabricated some components in the drive train for better handling . Not quite as smooth as stock , but handling is much better .

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Snag

There's still no fixed relationship between degrees of turn and torque in foot-pounds or newton-metres - it depends on thread pitch and Youngs modulus of the nut, bolt and objects being joined. So the whole premise of the OP's question was a bit flawed.

Given that torque wrenches are a standard piece of kit in any engineer's toolbox, it seems strange to specify that cylinder head bolts should be tightened by a given number of degrees, which is more difficult to measure. Either way works, but one way is more logical than the other.

It's like the age-old UK-versus-USA debate about whether cooking ingredients in a cake should be specified by mass ("5 oz of flour" - UK) or volume ("2 cups of flour"). As a scientist, I'd always measure solids/powders by mass, not volume - but then, being British and taught by my mother to weigh out cake ingredients, maybe I would say that ;-)

Since WWII there have been a variety of methods used for determining proper bolt tension -- in production. For service work, most methods are less tha n accurate.

One of the first of these production methods was a "degrees after yield" me thod in which the torque wrench sensed the onset of yield, and the final te nsion was specified as a certain number of degrees beyond the yield point.

This method was still in use in the '70s, when I was reporting on it. Maybe it's even in use today; I haven't looked. But the latest production method s use some method of measuring actual bolt stretch after yield, with precis e sensors in the wrench mechanism to detect the onset of yield.

The reason I didn't reply to the OP is because there are several issues inv olved. The simple answer is to try one -- torque it as specified, turn it a n additional 45 degrees, and note the torque at that point.

But the whole procedure is pretty loose to begin with. If the bolts and nut s are perfectly dry, you get one value of preload. If there's a spec of oil in there, you get another value. And so on. Trying to get too precise with it probably will leave you chasing your tail.

But it probably doesn't have to be that precise to begin with. The latest e ngines require bolts to be very precisely preloaded. Older ones don't -- be cause they couldn't, and they spec'd the bolts accordingly.

Caterpillar uses a system where you torque the bolts twice and then turn a specified number of degrees.

C-15 Engine main bearing capscrews: step 1 = 95 Nm, 70 lb.ft step 2 = 260 Nm, 190 lb.ft

Torque to angle is very much in use and actually gaining ground. In most cases you start with a new OEM bolt/nut/stud and torque to a number, then torque to a specified angle. These same fasteners are replaced every time as they are torque to yield.

replying to Bob Engelhardt, Levatator wrote: Thanks for 2 Things People. Thanks for this thread. Very Informative , and thanks ... My head now hurts.

You need to be more specific. degrees: of temperature or angular measure? Art

How much ft lb is 90degree

Study this to learn why there is no single answer.

"Torque is used to determine the initial preload developed in a fastener during the snugging operation. Regardless of the external factors that can influence torque, this serves as a relatively accurate way of ensuring that slack is removed from the assembly before tightening. The turn of the nut method is a more reliable measure of the further increase of tension of a previously "snugged" bolt. Once the slack has been taken out of the assembly through the use of torque, it is easy to determine the amount of turn needed to reach the proper preload for the bolt."

-jsw

This goes further to explain what I learned in college about how threaded joints fail.

The section on static failure assumes the bolt stretches more than the nut. In a turnbuckle the barrel can be sized to stretch enough to more evenly distribute the load along the eyebolt threads.

-jsw

If this is a serious question, you need to think about what it is that one is trying to accomplish by torquing bolts to a specification. The object is not to twist the bolt a certain amount, but to ensure that the proper clam ping force is being applied to the parts being bolted together.

In that case, the measurement of torque (in foot ponds) is pretty much mean ingless, as it only defines how hard the tool had to twist on the bolt head to get there. There are plenty of variables that can affect that measureme nt - lubrication being a very obvious one.

Snugging up the assembly and then applying a certain number of degrees of t wist to the bolt will tell you that you have stretched the bolt by a certai n distance (based on thread pitch and degrees of rotation), and THAT can be directly converted to clamping force.

OTOH, if this question was asked just to be cute, nevermind.

snipped-for-privacy@gmail.com on Sun, 8 Oct 2017 20:57:25 -0700 (PDT) typed in rec.crafts.metalworking the following:

Under what conditions?

After all, I can turn a bolt 90 degrees and have zero torque in ft-lbs on it.

-- pyotr filipivich "With Age comes Wisdom. Although far too often, Age travels alone."

Gunner Asch on Mon, 09 Oct 2017 02:16:31 -0700 typed in rec.crafts.metalworking the following:

Ah - forgot that. Three pfund Finnish flax per microfortnight.

-- pyotr filipivich "With Age comes Wisdom. Although far too often, Age travels alone."

Yeah, but the data he failed to provide: is that centigrade or fahrenheit? Coarse or fine thread? Bolt or screw? Brass, steel, wood, or nylon? Relative humidity and temperature high or low? Is it a full moon? What is the biorhythm schedule of the bolt? I refuse to work under these conditions. OMG, where's a safe space? Reeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee!

- I've figured out why we have Dems. Uncle Siggy told me:

Most people do not really want freedom, because freedom involves responsibility, and most people are frightened of responsibility. --Sigmund Freud

Unfortunately, some Reps are that way, too. (see CONgress)

Larry Jaques on Tue, 10 Oct 2017

LOL.

Yah know, if the degrees are Centigrade, it might be too hot to pick up in the first place.

-- pyotr filipivich "With Age comes Wisdom. Although far too often, Age travels alone."