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-   -   Torque wrench recommendations (https://vansairforce.net/community/showthread.php?t=202904)

BillL 01-17-2022 08:22 AM

Quote:

Originally Posted by Desert Rat (Post 1582661)
Snap on. A good torque wrench isn't something to skimp on.

An AP friend uses a snap-on ($$$$) with inserted end tools, it is excellent for using where only an open end wrench will fit. Ratchet head, and crowfoot is really dicey but works. $50 for a single 3/4"open end insert indicates how pricey it can get.

CDI is snap on w/o the lifetime service.

rongawer 01-17-2022 08:27 AM

Harbor Freight Quinn
 
No, seriously...

I have a CDI 1/4" digital torque wrench and a Snap-on 1/2" digital, but thought to upgrade my 3/8 Snap-On to a digital as well and bought a Quinn 64915 3/8" digital to experiment with.

Having an excellent mechanical research facility available at work, I tested my torque wrenches using weight standards in the lab, I found the HFT 3/8" with 2.1% error at 50 pounds (51.05 lbs) and 1.72% at 100# (101.72 lbs) in the CW direction. And then about 2.8% in the CCW direction for both weights. I tested each weight 5 times and averaged the error for each direction. For comparison, my mechanical Snap-On was closer to 3% in both directions - still within the certificate +/-3% tolerance. Note that most torque wrenches have a tolerance of around 3%, although I've seen some provided as high as 5%.

I do very much like my CDI torque wrench, and in reality, except for the engine case, cylinders, spark plugs and wing attach bolts - a 1/4" drive is all you really need to assemble an RV (er...pretty much any GA aircraft). So if you're going to spend a lot of money, spend it on the 1/4" torque wrench.

However, for considerably less money, I recommend buying the HFT Quinn line of torque wrenches,

TIP: the highest inaccuracy of a torque wrench is typically within the first 1/3 of range - target using the middle third to 100%.

Everwild 01-17-2022 08:42 AM

So much good information here!

Am I correct in thinking that a dial or split beam type wrench is necessary in order to measure the "friction drag" and then add it to the standard torque value?

I suppose you could find the friction drag with a click type through trial and error?

Strasnuts 01-17-2022 09:08 AM

+1 snap-on
 
Self calibrating digital snap-on. Never looked back at the cost after using so many times.

rongawer 01-17-2022 09:10 AM

ASME
 
The Van's KAI Section 5 has a very good description of torquing and discusses friction drag, which is technically "prevailing torque". I recommend reading that section rather than restate it all here.

Prevailing torque is almost always within 5% of the total torque, but more on smaller fasteners, less on larger ones (depends on the fastener retention mechanism, i.e. elongate thread, nylon locking, lock washer, etc...) and whether dry or lubricated threads, or if it's a previously used fastener. I wouldn't stress over it, just measure it.

In reality, most fasteners have +/- 5% torque tolerance available - some much more. It lines up well with the 3-5% torque tolerance of torque wrenches. It's almost like a bunch of engineers got together and planned it that way ;)

More food for thought - how many people actually get their torque wrenches calibrated every 12 months (or a certain number of cycles if more often)? It's actually the ASME standard and required for most certified work. But I'd guess not many folks do, especially for personally owned torque wrenches. I'm pleasantly surprised when folks even USE a torque wrench. I've observed many people, certified mechanics at that, use the "that's about right" torque setting with their "calibrated" hands.

So, the fact that you know the required torque setting, are actually using a torque wrench (properly I hope) and measure the prevailing torque first, then add it to the final torque - well, you're ahead of a lot of folks. Now, if you're doing so with a wrench with a known, valid, calibration, you get bonus points.

rongawer 01-17-2022 09:18 AM

Quote:

Originally Posted by Strasnuts (Post 1582698)
Self calibrating digital snap-on. Never looked back at the cost after using so many times.

Love your stuff man....sorry to be the kill-joy, but if the self-calibrating method you referring to is the calibration that occurs when turned on, it is misleading and really means self re-zeroing. It doesn't actually calibrate the accuracy of the mechanism, but it does ensure you automatically reset the mechanism, unlike a mechanical wrench which should be stored at or near 0. Snap-On has an excellent calibration service center if you choose to have this done. Or you can perform the calibration steps yourself using a standard weight and the wrenches' internal cal program described in the manual. You can make your own standard weight using water at a known temperature if you are that motivated as well.

BTW, all of the digitial torque wrenches I've checked, which include Snap-on, CDI, Mac, Irwin and, yes, even Quinn, have a self-calibrating feature when you turn it on.

"Tools, like the aircraft they keep in the air, also need proper and routine maintenance. Tools get dropped, misused, even wear out, and our calibration laboratory offers the equipment and expertise to get your tool's torque spot-on when it's accuracy gets a little off.

swordtail 01-17-2022 06:53 PM

https://www.harborfreight.com/hand-t...ter-63917.html

rv9builder 01-17-2022 08:20 PM

I have a 1/4”-drive beam style torque wrench similar to this one that works pretty well for determining prevailing torque and for torquing AN-3 bolts.

https://www.amazon.com/Neiko-03727A-..._t1_B07BFGN53Y

I also have a CDI 10–50 inch-pound, 1/4-inch drive that I bought for AN-3 bolts. In tests, the beam wrench and CDI have had very similar readings.

https://www.protorquetools.com/cdi-1...ch-dual-scale/

rongawer 01-18-2022 10:51 AM

if you are already using a digital torque wrench, you can set most of them to a peak setting. And then check prevailing torque with the highest torque saved for reference on the torque wrench digital display.

My CDI wrench keeps the value displayed for something like 15 seconds. I then update the final torque setting on the wrench and continue torquing.

Strasnuts 01-18-2022 10:54 AM

Quote:

Originally Posted by rongawer (Post 1582701)
Love your stuff man....sorry to be the kill-joy, but if the self-calibrating method you referring to is the calibration that occurs when turned on, it is misleading and really means self re-zeroing. It doesn't actually calibrate the accuracy of the mechanism, but it does ensure you automatically reset the mechanism, unlike a mechanical wrench which should be stored at or near 0. Snap-On has an excellent calibration service center if you choose to have this done. Or you can perform the calibration steps yourself using a standard weight and the wrenches' internal cal program described in the manual. You can make your own standard weight using water at a known temperature if you are that motivated as well.

BTW, all of the digitial torque wrenches I've checked, which include Snap-on, CDI, Mac, Irwin and, yes, even Quinn, have a self-calibrating feature when you turn it on.

"Tools, like the aircraft they keep in the air, also need proper and routine maintenance. Tools get dropped, misused, even wear out, and our calibration laboratory offers the equipment and expertise to get your tool's torque spot-on when it's accuracy gets a little off.

Good point, thanks for the clarification. That was misleading.


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