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16th May 2019, 17:34 | #1 |
Gets stuck in
75 CDT Conn SE Auto saloon Join Date: Jun 2010
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How much torque to shear an M8 12.9 bolt
Quick question ( I have googled it but couldn;t find an answer ).
I have a job lined up at the weekend that involves removing M8 thread Bolts from an alloy cylinder head, they are 12.9 - ( there are 9 of them and they attach the CAT ). Can anyone suggest a torque where they will start to shear. TIA Bap |
16th May 2019, 17:56 | #2 |
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Assuming the bolts were torqued into the head correctly and the thrads are clean, I'd say they will undo without shearing, however tight they are. On the other hand, if the threads are corroded together, I guess that changes things. There are lots of data online about the shear strength of 12.9 bolts, but how that's translated into a torque wrench value I couldn't guess. Is there anything in these links that you can understand?
Click 1: https://itstillruns.com/129-bolt-she...-11415080.html Click 2: https://www.wtools.com.tw/STANDARD-B...G-TORQUE.shtml Click 3: https://www.amesweb.info/Screws/Metr..._Strength.aspx There are lots more, little of which I understand. TC |
16th May 2019, 18:04 | #3 |
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I would not worry about that at all. The bolts will come out, and will tear the aluminium before they shear. Provided they are not corroded.
If you are worried, soak them in penetrating oil for 24 hours before you remove them.
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