Association of a shear bolt with a tension nut 1

[shingouz]

Hello,
I am sorry in advance if my question sounds stupid but is it possible to assoociate an shear bolt (hi lite) with a traction nut (12point..)?
Many thanks

 

[rb1957]

if you're asking about replacing a collar with a nut ... yes, but you might need to specify an installation torque (to represent the effect of the collar).

if you're asking about combining a shear bolt with a tension nut ... yes, i think this is pretty common; i think tension nuts are slightly lighter than shear ones, though it might be that the shear CSK is less than the tension bolt, and if things are not tension critical then why not.

 

[WKTaylor]

shingouz

A male threaded fastener [bolt, hi-Lok, etc] designed exclusively for shear has a head and thread to match for the OBVIOUS benefit of weight/spces/cost savings. IE: shallow head [small filets] and short threads to accomodate a matching low-height shear rated nut, with just enough thread protrusion with a thin washer to be safe.

Likewise, a male threaded fastener [bolt, hi-Lok, etc] designed primarily for tension/shear has a head and thread to match for the OBVIOUS benefit of tensile strength and fatigue performance. IE: deep head [large filets] and relatively long threads threads to accomodate a relatively deep ["thicker"] tension rated nut with a thick washer, with just enough thread protrusion with a thick washer to be safe.

When You deliberately try mixing and matching shear rated parts [nut, bolt] with tension rated parts [bolt, nut] You generally get the worst of all worlds.

Tension rated bolt with a shear rated nut is a heavy[ier] shear rated fastener system [limited by the nut]. CAUTION. a shear rated nut has to be torqued to a lower preload value than a tension rated nut to prevent damage to the nut [stripping] during installation or loading cycles. This may cause inadequate joint clamp-up pre-load.

Shear rated bolt with a tension rated nut may be physically impossible to assemble because the deeper nuts will not accomodate significant grip variation even with a thin washer; and the nut will most likely ride-off the threads/tip of the bolt and NOT pass safety inspection. IF the nut is torqued to the value for a shear rated nut, then joint preload is very low and nut may eventually loosen [unless by some miracle the nut is fully engaged on the threads]. IFthe nut is torqued to its nominal value, then bolt head distortion/failure will occure during installation or in-service.

Now having said all this, I know of a few nuts[collars, etc] that have relatively high strength and have relatively low height, that can be mixed with either tension or shear rated bolts. I these cases, the pre-load torque value MUST be defined/controled to ensure proper performance of the fastener installation [shear or tension]. These combinations must be carefully thought-out and are still relatively low strength [usually limited to 95-KSI shear and 160-KSI tension rated fasteners].

Regards, Wil Taylor

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