2nd Gen Non-Engine/Transmission DIY Torque Wrench 'Calibration' Check

[tomblue01]

This is a simple method to see what your TW reads. There are better methods out there [check youtube], but I used what was available.

Bench Vise; Measuring Tape; Masking Tape; 25# & 45# weight [not a dumbbell] borrowed from a relative's local fitness club; Parachute Cord [aka 550 Cord]; Calculator. Also used: piece of cardboard and cloth to protect the square drive.

1. Pick a spot on the handle of your TW. Measure distance from the midpoint of the square drive to this spot. Mine was 19". Line up the edge of the tape on one side of mark or the other. [I just put tape in the center of my spot with a pen marking off the distance. However, the tape gets beat up from the testing, so it's best not to have your cordage rest on the tape.]

2. Set your TW according to the following formula:
...Torque = Distance x Weight. Since I dealt in foot-pounds: Distance = 19"/12" per foot. Weight = 25#. Torque = 1.58ft x 25# = 39.5ft# --> sets TW to 40ft#.

3. Secure the TW in the vise. Protect the square drive. I tried using a sacrificial socket, but it will turn in the vise.

4. Tie the weight with your cordage and then proceed to gently hang the weight at the spot you picked on your TW. Lower the weight very slowly else you'll set off the 'click' in the TW [false positive]. With the weight hanging from the handle, note whether or not your TW made the 'click'. Adjust TW & repeat until you find the point where it clicks.

Now you can see if you are on target, high, or low!

5. Change weight. 45# --> 71ft# of torque [@ 19"].

6. Change weight. 70# (combining both weights) --> 111ft#.

Is your TW consistent? I hope so, for now you know how your TW performs.

_____

In the pic, the tape had torn, so I removed it. The camera angle also makes it look like the weight is touching a nearby box -- it did not.

 

[tomblue01]

If your TW is $$, you might not want to use this method.
I slightly marred the surface of the square drive. In the pic above [post #1], you'll notice that I didn't use a piece of cardboard along with the cloth. Ooops. [It still accepts sockets alright.]
I used cardboard [along with cloth] with my 3/8" drive TW, and that did fine. YMMV, of course. Hence the 'disclaimer'!

 

[tomblue01]

My 1/2" drive Craftsman 150ft# {2yrs old, mild use, stored at lowest setting} was consistently ~6% high. This means that everything I've fastened with it has a lower value than what I desired. From now on, I can set the TW to 6% more than what the manual specifies, and I'll be right on target.

My 3/8" drive Tekton 80ft# {same stats} was not consistent, except that all the TW values were lower than expected. 8% low @ 25#. 4% low @ 45#. 10% low @ 70#. This means I've over torqued the bolts. 10% doesn't bother me much, and now that I know I can compensate for its inaccuracy.

Cheers!

 

[Timd32]

If you box them up give me the weight and size of the box, my shop can do them for you. I will send you a FedEx slip to drop them off at a local place.

We don't have the $88k full doble beam calibration machine, but our units all in are like $3500, .5% and 1% NIST traceable, calibrated annually.

Don't forget you might have a 5% wrench, most of ours at 3% wrenches CW, and 6% CCW. So don't fret too much.

I have 2 models .5% accurate 3/8" drive 25-250 inch lb. And 1/2" drive 25-250 foot lb. Adapter to do all sizes.
These are the CDI ones.
www.protorquetools.com/1-2-dr-25-250-ft-lbs-cdi-digital-torque-tester-2503-f-dtt/

Then we also have a Norbar tester 1% 7.3 foot lb - 258.? Foot lb.

https://www.protorquetools.com/1-2-...rucheck-plus-350-digital-torque-tester-43222/

Also just a disclaimer this would be a free service, don't want to solicite any thing out side of the proper approved vendor area.

 

[Timd32]

Item # 00931425000P Model # 62001

Says it's a 4% wrench. If this is the same unit.

There might be some margin of error in that set-up. hey your trying something new.

Craftsman Micro-Clicker 20-150 Ft Lbs Torque Wrench features a 1/2" drive
Accurate to +-4% of load requirement
Provides readings in foot-pounds and Newton-meters
Locking feature adjusts quick and easily
Click feature makes the right torque clear and easy to read
Scales stamped into housing show inch/metric torque settings
Redesigned grip delivers hours of comfortable use that won't wear out
Built from a combination of tough steel and plastic

 

[tomblue01]

Yeah, Tim, that's the model. It's dropped in price since I bought it... I find that unsettling. In any case, it's not worth the trouble for recalibration. Thank you, though. When I upgrade to a better model, I might take you up on the offer!

 

[Timd32]

Maybe I should have torqued my fan hub pulley bolts!

I can see I actually might have used antisieze on those, I'm not going to be able to tear into that for 2 days it looks like. I antisieze almost everything which may have not been a good thing on those. Or that fan hub wrench when it wraps around the heads of the bolts loosened up some when I was banging on it. So all the torque specs and testers don t do jack, if the actual bolts are loose.

There is no % of tolerance on those fan hub wrenches, listed in what I could find.

 

[JR]

My Wright torque wrench states 4% accuracy @ 20% of the scale (Midway). The further you go toward either end of the scale the less accurate any wrench will be, although I suspect they probably don't vary by more than a few percent max if any.
It also states in my manual recal is recommended after 5000 uses or annually, which ever comes first.
I've checked my wrenches occasionally with a torque tester (+-3%) and they are within 5%
The bigger variable is the use of lubricants (or not) on bolts. Each antisieze manufacturer has different recommendation for torque recalcs. Chesterton Nickel (my personal preference) claims a balanced coefficient of friction which eliminates torque recalculations. Bostik recommends anywhere between a 15% reduction all the way up to a whopping 41% reduction in torque depending on type used. Other factors that alter torque are wether or not the head of bolts and nut faces are lubricated. Lots of variables that often go over looked.