Correct turning side of tightening bolts, nut or bolt head?

[ABA102]

I just want to seek any clarification or actual requirement from a code regarding on which side (nut or bolt head)should be as turned when performing bolt tightening. Is there a big difference on accuracy of specified torque value when toque is applied on bolt head rather than on nut.

 

[Agent666]

Usually the nut is turned. Sometimes for captive bolts where the nut is inaccessible I've seen the bolt turned (with washer under bolt head).

Only way you'll tell if torque is different would be to calibrate the procedure if using torque to tighten. Otherwise you can use other methods like load indicating washers or part turn methods.

 

[darthsoilsguy2]

turning the nut is normal.

Pretensioning is the only time that this should be a concern. It is more difficult to correctly mark the bolt/nut/base-metal for turn-of-the-NUT method if you come from the bolt head side, and it is in the name too. RCSC allows for "turn of the nut" method of pretensioning to be done by turning the bolt head if turning the nut is impractical.

With regards to other pretensioned bolts.... Maybe Squirt-Washers have manufacturer's instructions that tell you to come from the nut side..... spline bolts have to be done on nut side because of the wrench involved.... it seems like an inspector wouldn't be stepping out of line to require that installation be done per the installation method used during field skidmore testing of bolts.

I'm not aware of any code references that chime in on snug-tight bolts, and i can't see why it would matter considering the already weak spec language 'full strength of an iron-worker' on those type of connections

 

[Ron247]

I would think turning the bolt would give incorrect readings because you are rotating the shaft also. If the 2 holes you are bolting through are misaligned and you do not have a nut at all on the bolt, I know you can get a torque reading because torque is resistance to turning.

I have removed a nut and had to beat the bolt to get it out. If I had to beat it to get it out, it would have also registered on a torque wrench.

 

[dauwerda]

As darthsoilsguy2 pointed out, for pretensioned joints the RCSC (Section 8.2) does allow to turn the bolt rather than the nut provided that the washer requirements in section 6.2 are met.

 

[human909]

Your are also introducing permanent torsion stresses into the shaft which ultimately would mean a weaker connection. How much so? Well that is an interesting question. But if your bolt requires significant pre-load then you will also be putting significant torsion on the shaft.

I've broken bolts before and twisted the shaft of a tyre wrench before, torsional stress shouldn't be underestimated. (Both case hardly structural strength but this is bare hands.)

 

[ABA102]

Thank you all for your responses.
So far, I can use implement RCSC section 8.2 as per discussed by darthsoilsguy2 and dauwerda but only on pretensioned or preloaded bolts.

 

[Lomarandil]

Per Agent and Dauwerda -- whichever end has the washer.

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just call me Lo.