Top triple-clamps on the cheap?

[Paul Heim]

We have customers who ask,"Can we use stronger bolts?  Some of ours are 
breaking!"  I ask them:

a.    To what value are you torquing them?"
b.    How many times have you used them?

We recommend they be replaced with new each time a unit is disassembled, and 
that they be torqued to spec.  No one does this.

Bolts that are subject to cyclic loading are going to fail by fatigue if 
overtightened.  If undertightened, usually something leaks or falls apart. 
Torque to spec and you'll stand the best chance of avoiding both.

Paul in Ohio
----- Original Message ----- 
From: "Buehrle, Michael" <Michael.Buehrle at ottawa.ca>
To: "GPz List" <gpzlist at micapeak.com>
Sent: Monday, October 01, 2007 3:48 PM
Subject: RE: Top triple-clamps on the cheap?


> The subject of torquing fasteners has been kicked around frequently here 
> at my workplace lately. We have 20(2 mil.$/each) high speed centrifuges 
> built somewhere around Philly that are mechanical marvels.  Unfortunately 
> the old mechanic who services them thinks torquing is Voodoo and 
> unnecessary. Needless to say he suffer frequent failures due to 
> loose/damaged fasteners.
>
> A recent demo with a bench readout, torque teaching aid showed me just how 
> critical torque is: An overtightened bolt can never be reliably torqued 
> again, lubricating threads,adding washers all greatly effect how much 
> torque is required. Even a bolt that has been correctly torqued previously 
> will lose up to 30% of it's holding strength on reuse.
>
> Mb