Comments on: Tension vs. Torque Explained (sort of…)

By: Hevii Guy

Hevii Guy — Sun, 22 Mar 2009 16:39:32 +0000

Direct Tension Indicationg washers provide a false sense of security: They cannot indicate whether the joint has been overtightended. Neither do they provide a means of checking load migration after initial installation.
Skidmore-Wilhelm machines provide an accurate indication of torque to load but ONLY on the exact fastener being measured under the the conditions experienced in the device AT THAT TIME. Once the tested wrench is used in the field, myriad friction factors and load interactions mean that all bets are off; one has no way of knowing what the actual load will be – it’s still a “guessing” exercise unless load is verified AFTER the bolt has been tightened and then again, after all of the other bolts have been tightned (to compensate for load transfer)

By: Adam Oakley

Adam Oakley — Mon, 07 Apr 2008 16:34:45 +0000

Galliou » It is hard to say if these calculations would be very accurate for anchor bolts. The biggest uncontrolled variable when determining torque is friction. Since the surface between the bolt assembly and the joint surface in the field can vary greatly it is difficult, if not impossible to accurately estimate torque for anchor bolts. One option would be to consider load indicating washers. This washer will give consistent tension values regardless of environment.

By: Galliou

Galliou — Mon, 07 Apr 2008 16:30:42 +0000

Is the “Bolt Torque Chart” applicable for anchor bolts?

By: Adam Oakley

Adam Oakley — Tue, 08 Jan 2008 23:43:00 +0000

Bryan Carr » The formula from Industrial Fastener Institute (IFI) “Design of Bolted Connections” (M-64), used to determine values for our toque chart states it is meant for, “… steel bolts in their as-received condition.” Although, IFI goes on to state there many factors (surface texture, material hardness, thread series) that only have a “modest effect” on the torque-tension relationship. The primary influence on torque calculations is coefficient of friction. Again, the only “correct” way to establish an accurate torque value is to test the fastener in their actual joint application.

By: Bryan Carr

Bryan Carr — Tue, 08 Jan 2008 23:22:37 +0000

Should you torque a bolt to a recommended torque even when using helical spring lock washers?