A few days ago I was torquing a suspension bolt and I just had that feeling that I was going way too tight .... and I was seriously starting to wondering if my torque wrench is no longer accurate!
It bothered me a lot - so I found out how to make sure my torque wrench is in fact accurate and now I can sleep at night knowing my repair is correct.
I put together this short video showing just how easy the process is.
I was spoiled for years- Worked at Coast Guard Air Station SFO and they had a torque calibration station- Set the torque on your wrench, hook it up and pull it till it clicked- then look at the digital readout. They finally eliminated those in favor of sending the wrenches out for calibration at Travis AFB. Since approx' 2013 I haven't checked the cal on my craftsman and also my small ones........I'll check it to it's max by sitting on the handle!
Also, very important; As said above take it down to the lowest setting when not in use- my two larger ones go down to 20 Lb/Ft....Always set it there (Don't go below lowest setting either)
Also, very important; As said above take it down to the lowest setting when not in use- my two larger ones go down to 20 Lb/Ft....Always set it there (Don't go below lowest setting either)
I understand about releasing the tension on the spring inside the torque wrench when it's not in use, but what difference does it make if the adjustment is turned a bit beyond the lowest setting?
[This message has been edited by Patrick (edited 10-15-2019).]
Some - Not all- Torque wrenches are set up so that if you go below their lowest setting you bend the spring that sets the tension. I got this from two sources- a guy in a US Navy Calibration lab, and a Snap-on guy- said exactly the same thing but maybe 20 years apart....It all so was stated in the manual with my medium(75 Lb/Ft) torque wrench I bought around 2002.
Interesting thing I noticed once; Re-installing the heads on my 460 Ford jet boat engine- they go up to 140 Lb/Ft....One time I used a 2 foot long TW and it was all my buddy could do to keep the engine (Sitting on 10 QT pan on cardboard) from spinning around. 6 months later I had to redo this because my experimental mufflers had blown the head gaskets...Used a rental 4 foot TW- It was easier for my same buddy to hold the engine.....I understand it was easier for ME (Longer lever) but easier for him...?
Some - Not all- Torque wrenches are set up so that if you go below their lowest setting you bend the spring that sets the tension. I got this from two sources- a guy in a US Navy Calibration lab, and a Snap-on guy- said exactly the same thing but maybe 20 years apart....It all so was stated in the manual with my medium(75 Lb/Ft) torque wrench I bought around 2002.
I suppose it's also possible that some people turn the adjustment way below the lowest setting... which might do something bad that just turning the adjustment a bit below the lowest setting wouldn't do.
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Originally posted by cvxjet:
One time I used a 2 foot long TW and it was all my buddy could do to keep the engine (Sitting on 10 QT pan on cardboard) from spinning around. 6 months later I had to redo this because my experimental mufflers had blown the head gaskets...Used a rental 4 foot TW- It was easier for my same buddy to hold the engine.....I understand it was easier for ME (Longer lever) but easier for him...?
Me thinks one of those torque wrenches was out of spec.
I get that but here is the interesting "Contradiction" of the way they SHOULD be out of spec; When I used the short TW and my friend had trouble holding the engine, the head gaskets failed within 6 months (Admittedly from my experimental Mufflers), while when I did it with the 4 foot long TW, the head gaskets are still working great- no leaks of any sort; I torqued them back in 2004....so that is 14 years trouble free- and I take my boat out to the Delta at least 20 times for ski rides and such every year, and then also up to Trinity lake for 2 weeks every summer....60-80 hours every year.
You'd think the "easy one" would have been the time the gaskets failed......
A vitally important part of using a torque wrench; often overlooked, is to exercise the torque wrench prior to use. Not a walk in the park but set it at 60% ish of the scale and pull 3 or more times. There is very often a significant difference atwix those initial readings and the proceeding pulls. If you are feeling particularly diligent you could repeat this excercise when set to the reqd torque setting. Especially important to the DIY user where the torque wrench may not have seen any action for weeks/months.
As to winding them off after use. It was drummed in to many apprentice heads over many years. It depends greatly on the design and components used.
For a shim tensioned torque wrench, backing off too far can remove all tension from the shims and allow them to rotate in the stack or collect detritus which can in turn alter tension. Particularly important for larger "clutch" style torque wrenches such as the norbar 5r.
Click and cam style that are spring/rod operated can normally be wound fully off.... But there are sometimes plastic drive/handle lock gears that have a hex inner section, if the torque wrench is over enthusiastically wound off every time, they can stick closed and the extra ooomph to release every time will eventually round off this hex section.
Norbar now do not advise to fully wind off their wrenches.
Originally posted by olejoedad: Always reset the torque wrench to zero after use to extend the calibration life of the tool.
Yes, Zero. But never loosen more that many do allow. Loosen < Zero can allow the "click block" to move inside many torque wrenches making to read way off or not working.
I've seen expensive wrenches need pro fixing and recal because of this. Many are used where they need certs to show tool reads correct w/in ±X%.
I return to Zero after use every time because don't use them much now.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurassic Park)
Okay, I guess I've learned something about torque wrenches that I didn't previously know. I'll be diligent from now on about not adjusting my torque wrench below it's lowest setting when I've finished using it. Thanks to all who chimed in on that matter.
Originally posted by Patrick: Okay, I guess I've learned something about torque wrenches that I didn't previously know. I'll be diligent from now on about not adjusting my torque wrench below it's lowest setting when I've finished using it. Thanks to all who chimed in on that matter.
While Some TW may like being fully unwound but unless your have doc's to prove that better to assume to set to Zero or lowest marked setting. (Some don't have a true Zero. Most are high range units for 200 or a lot more ft-lb not sold at most retailers. Often can hurt you just falling on your foot etc.)
Basically most "Click" TW are same idea. In Short, Normally... Head will move a little on the pivot as "click block" (a block, cam or whatever) tries to rolls when spring and "hammer" can't keep them straight under pressure. "Hammer" is just a name for part(s) between spring and "block." Problem is "Click Block" is a loose part in a lot of them and w/o enough pressure the block can get out of position or worse. Depending on exact tool, Can do that w/o other issues or like vibration when stored can shake it out of correct spot.
I have cheap HF because is good enough for how much I need them. Still have a old Torque Limiting Screwdriver for computer work still cost $250+ for range of 0 to 100 in-oz. (under Utica brand and rerated 20-100in-oz.) That will click and spin all day when you reach torque. Sim to power drill/drivers w/ limit clutches.
(Is there a Pittsburgh in China?) 
