Date:         Mon, 14 Oct 2002 22:51:44 EDT
Reply-To:     FrankGRUN@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Frank Grunthaner <FrankGRUN@AOL.COM>
Subject:      Some Comments on the Torque Wrench Discussion
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The debate over the merits of clicker vs beam torque wrenches moves me to a
few comments. In my experience, I have used 4 different types of torque
wrenches: the trusty beam, the widely available adjustable clicker, the dial
(actually a beam and gear mechanism as has been pointed out) and the fixed
calibrated clicker.

To begin, I've been wrenching bolts for more than 44 years, the last 43.8
using a torque wrench. Most of that twisting has been done on automobiles
ranging from American iron, through German alloys, through French mystery
metals and on to Italian aluminum. My laboratory is often described as a
stainless steel palace. The UHV hardware ranges in value from about $75,000
to $1,500,000. The proper tightening of flanges is critical to avoid leaks
which can trash the experiments. Our typical operating pressures are below
10(-10) torr. To achieve these pressures, the systems are baked for extended
periods to peak temperatures of 235 C to 450 C. These thermal cycles are
particularly stressful for bolt preloads on copper sealing systems. Bolt
torque specs range from 14 foot pounds to 125 foot pounds. All bolts are
silver plated for thread lubrication. Noone works in that lab with using a
torque wrench on every bolt. Over the years, I've fired a few for just such a
transgression.

My advice is, however educated your hand or butt is, use the torque wrench.
Cheap insurance. Remember, no single time job is nearly as expensive as the
second or third redo to get it right.

Now as to the torque wrench issue. As far as I'm concerned, the key problem
here is calibration. Now the trusty beam and the disguised beam (dial) both
rely on the basic material properties of the beam. Anybody anywhere can
reestablish zero (bend the pointer or rotate the bezel). The adjustable
clicker can lose its calibration all too readily. Heavy over torque beyond
the click point. Sharp drop to concrete. Massive ingestion of oil, dust and
dirt. The real problem is with the adjustability. With adjustment comes the
need to calibrate often and well.

Now, the best wrench I use (used the same type for more than 30 years) is the
fixed calibration clicker. This wrench is available in a wide range of torque
values. One wrench, one value. For the lab, we use about 6 different bolt
sizes, so we maintain 3 sets of 6 different wrenches. Now these wrenches are
not ratchet drives, but rather use a replaceable box, open, Allen or torx
head. Used like a regular open or box end wrench. I have had these
recalibrated and never had one go out of specification.

For automotive wrenching, however, I use an adjustable clicker and a beam
wrench. The beam is usually a PITA to get just where I need it, so I never
(well almost) use it on an engine. Nope. I use it to calibrate the clicker. I
have a 1/2 inch drive beam and a 3/8 inch dial. I have appropriate box square
sockets to drive them with the 1/2, 3/8 or 1/4 inch drive adjustable clicker.
Just before use, I set up the clicker to the torque     I need, then on to
the job.

As part of this drill, I always clean the threads of any reused bolt by
chasing it with a die. I always use a MoS2 thread lubricant on anything
except exhaust manifold bolts. There I use a WS2 lubricant because of the
temperatures.

All the hardware I'm talking about are available from Craftsman, Mac, Snap-On
or from McMaster-Carr.

Just a comment,

Frank Grunthaner