fatigue life enhancement with hi-lite

huangyhg

fatigue life enhancement with hi-lite
dear all,
maybe somebody can explain what is the advantage of hi-lite over hi-lok regarding fatigue ? i have visited hi-shear site already, but not so much of an explaination that i can get from there regarding the above subject. what i am looking for is actually why can we install hi-lite with higher interference compared to hi-lok and how much. but i have recieved an answer from hi-shear already and according to them the higher interference that can be achieved with hi-lite is due to the different lead-in radius design. the remaining question would then be how much interference and fatigue life enhancement that can be achieved of joints using hi-lite compared to hi-lok.  thanks sparweb, for your suggestion to start a new thread.
regards,
hi-lok's have the feature of limiting the torque that can be applied to the collar when they are installed.  by not over-torquing, they are not significantly stretched, so the diameter of the fastener does not decrease, either.  there is some torque, though, so the hi-lok is okay for shearing loads.
hi-lites are a little different.  they have the features of the hi-lok that i described above, but the threading is changed.  there is an improvement in how the collar threads onto the pin that increases fatigue life of the fastener, meaning the collars for hi-lok and hi-lite are not interchangeable.  the different threading also reduces the size of the collars, cutting down their weight (hence the name).
there are also hi-tigue bolts, that have a slight bulb in their shank.  apparently, as you tap them into an undersize hole, the bulb cold-works the hole surface.  by burnishing it, a residual stress remains that improves fatigue life.  from reading about it, i expect that hi-tigues are much more expensive, too.
if sealing the joint is important, note that the sealed collars may not be available for all types of fastener.
steven fahey, cet
thanks sparweb,
but can we also obtain some slight cold work effect on the hole wall with hi-lite and hence increase the fatigue life of the joint ?
regards,
fatstress
i'm afraid i don't know the answer to that one.  i can't see how a hi-lite would be any different than a hi-lok in that regard... where's mr. w.k. taylor when you need him?
steven fahey, cet
fatstress... and you-too sparweb...
in a nutshell鈥?br>
hi-loks [hl] were the first generation fastener of it's type. designed for installation in close-tolerance clearance and transition-fit holes [i favor the term 鈥渘et-fit鈥濃