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Old 12-06-2017, 03:53 PM
scorleo scorleo is offline
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ABC of Torque angle - what does it mean?

I get the first part i.e. 8 NM or 6 lb/ft, what's the second specification and how does one apply?

Torque specifications:
M8x26 - 8Nm + 90
M8x92 - 8Nm + 180
M8x112 - 8Nm + 180

The above specification is for oil sump (aka pan) bolts on N51.

Thanks!
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Old 12-06-2017, 03:55 PM
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Torque to the indicted torque limit then the angle further to stretch the screw to maximum clamping force.

Note that Torque To Yield screws have yielded and are close to breaking and will not be properly reused again.
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Old 12-06-2017, 04:15 PM
scorleo scorleo is offline
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Originally Posted by Doug Huffman View Post
Torque to the indicted torque limit then the angle further to stretch the screw to maximum clamping force.

Note that Torque To Yield screws have yielded and are close to breaking and will not be properly reused again.
Thanks Doug! I get it
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Old 12-06-2017, 06:34 PM
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Quote:
Originally Posted by Doug Huffman View Post
Torque to the indicted torque limit then the angle further to stretch the screw to maximum clamping force.

Note that Torque To Yield screws have yielded and are close to breaking and will not be properly reused again.
I thought I got it first but I don't think I processed it correctly Once it's torque to the specs using torque wrench then am I using higher torque/regular wrench to meet angle spec?

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Old 12-06-2017, 06:46 PM
insightbrewery insightbrewery is offline
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Correct. Use the proper torque wrench to get it to the initial torque value, then use a regular ratchet/wrench to turn it the additional angle (so, 180 degrees = 1/2 turn), don't worry about torque for that. Go slowly of course so you don't snap a bolt or something.

If you really want to be anal, you can get torque angle gauges.
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Old 12-07-2017, 07:10 PM
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Originally Posted by insightbrewery View Post
Correct. Use the proper torque wrench to get it to the initial torque value, then use a regular ratchet/wrench to turn it the additional angle (so, 180 degrees = 1/2 turn), don't worry about torque for that. Go slowly of course so you don't snap a bolt or something.

If you really want to be anal, you can get torque angle gauges.
Thank you! I thought I wouldn't need torque angle gauge as you suggested but damn, the 26 mm length is supposed to be 60 degrees and not 90 as FCP Euro suggested on their site. I'm glad I cross checked Bentley and newTis, so I do need torque angle gauge because 60 is bit tricky compared to 90 and 180. Now I need to see if I can find in any of the local stores in No VA...
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Old 12-08-2017, 07:42 AM
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I think (in my opinion) you are reading too much into it.
I believe the intention of the additional angle is to make sure you tighten bolts evenly following the pattern that is provided in bentley or manual of your choice. So after the 8NM torque is followed for all bolts, they are tightened further to make sure preload is applied gradually and evenly. The problem is the bolts are now static and static friction is larger than dynamic, so that's why you have angle and not torque to overcome the initial static friction. Honestly 90 is quarter turn and 180 is half turn, you are ok approximating it, wouldn't worry about a few degrees off. 60 is just a nudge, smaller than quarter turn - done.
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Old 12-08-2017, 07:56 AM
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Originally Posted by Watchme View Post
I think (in my opinion) you are reading too much into it.
I believe the intention of the additional angle is to make sure you tighten bolts evenly following the pattern that is provided in bentley or manual of your choice. So after the 8NM torque is followed for all bolts, they are tightened further to make sure preload is applied gradually and evenly. The problem is the bolts are now static and static friction is larger than dynamic, so that's why you have angle and not torque to overcome the initial static friction. Honestly 90 is quarter turn and 180 is half turn, you are ok approximating it, wouldn't worry about a few degrees off. 60 is just a nudge, smaller than quarter turn - done.
Thanks Watchme! The problem is I'm OCD and by degree an engineer so that's the key issue .

Advance Auotparts is just next door and they have this gauge, I plan to pick it up this morning.
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Old 12-08-2017, 11:13 AM
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Quote:
Originally Posted by Watchme View Post
I believe the intention of the additional angle is to make sure you tighten bolts evenly following the pattern that is provided in bentley or manual of your choice. So after the 8NM torque is followed for all bolts, they are tightened further to make sure preload is applied gradually and evenly.
Dead wrong. As Doug stated earlier, the purpose of a jointing-torque-plus-angle specification is to stretch the bolt by a substantial amount, typically almost to the point of breaking, to develop maximum clamping force.

Normally, as you tighten a fastener the torque required to turn it steadily increases, because the bolt material is stretching slightly and applying more force to the threads (that stretch is what creates clamping force, not friction per se). Tighten it further (past the yield point of the material, hence the term torque-to-yield) and the torque required to continue tightening it will actually decrease, as the bolt material begins to take on a permanent stretch. That is why an angle specification must be used--the torque ceases to be a reliable measure of the clamping force being applied to the joint.
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Old 12-08-2017, 11:51 AM
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Quote:
Originally Posted by Zeichen311 View Post
Dead wrong. As Doug stated earlier, the purpose of a jointing-torque-plus-angle specification is to stretch the bolt by a substantial amount, typically almost to the point of breaking, to develop maximum clamping force.

Normally, as you tighten a fastener the torque required to turn it steadily increases, because the bolt material is stretching slightly and applying more force to the threads (that stretch is what creates clamping force, not friction per se). Tighten it further (past the yield point of the material, hence the term torque-to-yield) and the torque required to continue tightening it will actually decrease, as the bolt material begins to take on a permanent stretch. That is why an angle specification must be used--the torque ceases to be a reliable measure of the clamping force being applied to the joint.
Agreed completely, don't see how I am "dead wrong" though. There are multiple forces being engaged while tightening, my argument that torque is no longer accurate still holds as you pointed out. Did not know about the yield range of material being weaker than during its elastic elongation... thanks learned something new. I do believe the angle is also of purpose that you tighten all fasteners to torque spec, then do them all again for the additional angle turn to get them into yield range as you said.
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