×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

bolt material determination by torque tightening

bolt material determination by torque tightening

bolt material determination by torque tightening

(OP)
I have a M20 bolt with 8.8 embossed on it and a nut with 5 embossed on it ..i seek to check the material of both these two by tightening them at the recommended torque(calculated by knowing the listed proof strength of bolt against 8.8 and yield strength of nut as per grade 6) .any thread slippage at the recommended tightening torque will verify that the actual material of these two is not as embossed.is this the correct approach?

RE: bolt material determination by torque tightening

You will have to test the fasteners with an optical emission spectrometer or x-ray fluorescence to determine the material. SAE J1199 permits a wide range of steels with carbon ranging from .28 to .55 percent, and with customer approval low carbon manganese or boron steels can be used. The only aspect that you may determine with your test is whether your heat treatment is suspect but even then you will have to perform a hardness test to confirm.

RE: bolt material determination by torque tightening

First, you cannot test them against each other - you would need to mechanically test the nut and bolt seperately. Proof load is a good way to go for the nut mechanical property. You might want to instead machine a tensile specimen from the bolt so you can test UTS, yeild strength, and elongation as well and compare to 8.8. Note that the nut can also be checked for grade using composition (and you can confirm 8.8 composition for the bolt as well).

RE: bolt material determination by torque tightening

(OP)
thank you for your replies..

yes you are correct mrfailure..material composition test is a good way to identify the correct grade..how will i determine the proof load for bolt and nut?

how will hardness determination help determining the material grade of nut and bolt?

8.8 bolt is ISO right?

RE: bolt material determination by torque tightening

ISO 898-1 defines property class 8.8 for bolts. ISO 898-2 defines property class 5 for nuts. You should read these two documents to understand the correct testing methods.

These two fasteners are not a very good combination (the nut is not strong enough).

RE: bolt material determination by torque tightening

For proof load: The markins on the bolt and nut tell you what grade the material is supposed to meet. The proof load requirement is listed in the ISO 898 specs Cory mentioned. You would perform proof load testing in accordance with ASTM F606M. This will be done for you at a materials test lab that has the required fixtures you would need to perform the test. You would not perform this testing yourself.

The ISO specs will tell you the mechanical properties required for the different grades, so you will be able to determine conformance.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources