Victor,
The initial un-torquing value is the same for a short period of time.  Soon
after, even hours, it becomes a little less than the original torquing
value. One reason is that there is a little relaxation of the mated
materials and fastener threads with time and the clamping/torque values
diminish slightly.  Another is that when un-torquing, you are driving the
fastener "down" the ramp instead of up, if you imagine the fastener threads
as a ramp.  In all my experience, there is little or no significance to the
"un-torquing" value.  There are just too many variable involved.  When
tightening a fastener, the kinetic friction of threads and seating surface
of the fastener are what we sense as torque when we reach "tight".  When
loosening a fastener, we encounter the static friction of the contact
surfaces, which is higher than kinetic friction.  Depending on the nature of
the surface static friction can be slight, as with hard, smooth surfaces or
be considerable if soft, rough surfaces are involved.  Recall the nature of
lock washers that create high friction in the loosening direction.  Also
sometimes the seating surfaces may gall (cold weld) when tightening making
removal more difficult.

Hope this helps,

> Rainer G. Blomberg
> Honeywell -Space Systems Clearwater
> Staff Production Engineer
(727) 539-5534


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor G. Hernandez
Sent: Thursday, May 05, 2005 5:25 PM
To: [log in to unmask]
Subject: [TN] Torque

Fellow TechNetters:

   Can someone share their experience with the topic of TORQUE.   How is
the torque valve of hardware differ from the
value of Un-torqueing that same hardware.   Is the torque valve higher
than the un torque value or vice versa.

   Power FETs can be damaged when the plastic package exhibits a hole where
the bolt is inserted.
Not the typical TO220 or TO66 plastic style.

Victor,

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