bolt preload

[christophersrikanth]

thread725-272020
I am very eager to see the link (jpg image) mentioned by Tmoose in his post in the above thread. Can someone help? The image appears lost-if Tmoose read this-pls can you re-post the image?

 

[Tmoose]

Hi Christopher,

I think the picture was just a woodworking clamp like this one. With pivots at all screw interfaces.

http://img1.etsystatic.com/000/0/6188818/il_570xN.303638409.jpg

I think I was trying to say that even with a very short fastener length tightening the fastener still exerts a force (on the hapless creature trapped in the jaws). I think "preload" is the force exerted, not whether a significant hunk of fastener was stretched elasticly to generate the force. Short grip length is always a poor design feature on a hard working bolted joint because it is so vulnerable to preload loss from small amounts of relaxation, embedment etc.

The widely maligned torque/tension tables can be used to get a useful feel of how much clamping is generated by tOrQuinG a fastener of any length. I think the admittedly potentially more accurate Turn of the nut or bolt stretch methods are in trouble when used to secure thin parts like these.

http://image.musclemustangfastfords...ang_torque_converter+flexplate_bolt_check.jpg

http://c564296.r96.cf2.rackcdn.com/Articles/2011/11/10/n26-1211ae.jpg