Got a question I've seen conflicting answers on in my research so wanted to ask here.

I've purchased a couple of Park Tool torque wrenches. The TW-6.2 and the ATD-1.2 adjustable torque driver.

The instructions for the ATD-1.2 don't say how it should be stored - does it matter? Should I store at the lowest setting (4 Nm). It goes up to 6 Nm in .5 increments. Doesn't have a zero setting.

The TW-6.2 instructions say:
Dial torque setting to lowest point on scale after each use. Also, dial setting to lowest point when storing torque wrench.

Does the lowest setting mean zero (which it was set to right out of the box when I got it). Or the lowest non-zero value. I've seen both answers in my research and I wanted to know if it matters.

Also, do you have your torque wrenches recalibrated? If so, how often? If it's a Park Tools, do you send it to them? Is it worth the cost to have that done vs. just buying a new one?

Thanks in advance.

Reset torque wrenches to their lowest setting for storage.

I've never had mine calibrated. Would be interesting to see how accurate they are.

Not all torque wrenches go to zero. (I'm thinking of the 400 ft-lb unit in my shop)

Bring them to or just below the lowest setting, but not all the way bottomed out.

Every good quality torque wrench or screwdriver I've ever owned or used has instructions to store at the lowest torque levels. However, if you pay for good tools they often are for a higher level of precision than you need. So a torque wrench for use in aviation (as I understand it) will be calibrated fairly frequently. Some assembly shops use torque wrenches or screwdrivers that don't even have the torque levels labeled: you use a calibrator to get it to the right torque and lock it.

I calibrate my wrenches against each other (a click-type with a beam-type, for example). Or I use a weight an a lever arm. But I don't ever recall my torque wrench not being within the accuracy I need.

So the point is, to be sure store at low torque settings, but if you store at high torques it may not affect the calibration.

Thanks, appreciate the replies. So, if I got this right, it sounds like, for the ATD-1.2 - which has settings from 4Nm - 6 NM (no zero setting), leaving at 4 Nm is the way to go.

For the TW-6.2, it has a zero setting, but it s/b ok to leave at the next lowest setting after using it.

Thanks again

If they are cheapies it is a very good idea. My neighbor bought a Harbor Freight wrench that did not seem right to him, I check and it was so far off we took it back. Manager said for an exchange to wait until after the next sidewalk sale when he would have a new batch in the store as what he had was all off. Youtube has video to show the way.

A few more tips.

If a torque wrench has to be set down while using it, always set it down on its back with the driver facing up.

To the extent that it is possible, store the torque wrench in the environment where it will be used. For example, don't store the wrench in a 68° air conditioned house and then bring it into a 100° garage to be used. Wild swings in temperature and/or humidity can cause inaccuracies. A good calibrations lab will let a device sit in their facility for 24 hours before service so that the temperature and humidity can stabilize.


-Tim-

Thanks for the tips. Appreciate that as I'm home-mechanic-in-training so appreciate the advice.

For a couple years I worked at a place where all torque wrenches were signed out at their lowest setting with a calibration sheet. Upon return, lowest setting required, and were calibrated again before the next guy could check it out. If not returned in the required time frame, I don't remember if it was by end of shift or the next morning, you could get locked out of the system. I also work at places where torque wrenches are unceremoniously tossed into gang boxes with any other wrenches and hammers. I always turn them down, but seldom find them way.

Set them all to 11?

Not sure why storage requires setting to lowest level. My understanding of fatigue is that it comes from use. A car sitting on its wheels does not wear the springs out, it is the use of the springs when driven that wears them out. Perhaps I am incorrect. Please explain the logic of storing at lowest setting. Is there something else in the mix that can be forced out of calibration by not storing at lowest setting?

Lowest setting means lowest setting. I.e. as low as your specific wrench will go. "Zero" has nothing to do with it.

Also, if you get another wrench, pay attention to what it says in the manual. Some models recommend setting it to the lowest setting (like yours). Other models recommend setting it to just a little bit above the lowest setting (!).

In fact, I don't remember ever seeing a torque wrench that would recommend zero setting for storage. Those torque wrenches that go down all the way to zero typically recommend using low, but non-zero (!) setting after use and for long-term storage. I.e. set them to just above the lowest setting.

The popular recommendation to set torque wrenches to zero is usually given by ham-fisted self-proclaimed internet "experts" who learned if from similar kinds of "experts" on the Net.

Yeah, the ATD-1.2 manual didn't say anything about what setting to leave it at. For the TW-6.2, the instructions did say leave at the lowest setting so it probably did mean the lowest non-zero setting (even though it arrived in the box set to zero). But for a newbie, it was confusing.

My materials science classes were nearly 50 years ago but I suspect it may be the problem is creep, not fatigue, which would not be issues with other systems like you FD and RD or your auto and may be with the precision of a torque wrench. Stress below the metal's yield strength can slowly plastically deform the metal with temperature and time resulting in calibration errors.

On the click type wrenches, the thought behind setting them to the lowest setting is so that the spring (which compresses the deformable toggle) will take a set.

So, take the tension off.

FAA licensed aircraft / helicopter maintenance facilities check for calibration on tools within the last 12 months generally.

my "Interplanetary" torque wrench has a 1992 calibration sticker from JPL-Pasadena. However nothing bad has happened, it works fine.

Mark Petry
Bainbridge Island, WA USA

I just hang mine up on the pegboard when I'm done with it. It goes back to 0 all on its own.

Snap-on recommends storage of click type wrenches at the lowest setting. I always store my torque wrenches in their case and set at the low setting of the scale or one more turn past. I am an A&P/IA and when I was working as such my wrenches were calibrated if I recall every three months. The facility I worked in also had a tool for a quick check before each use especially if a critical torque. Yes, you can argue the cause, but I know as certainty that habitually leaving a click type torque wrench set at a working value will result in a tool that is not accurate and will need adjustment/repair. Do not use your torque wrench to run on a fastener, remove fasteners or general ratchet duty and avoid dropping them, hitting them with hammers or other squid moves as they will be damaged.