DIY torque wrench calibration - another SIP thread

OaklandF4i

OaklandF4i

Darwin's exception
Another shelter in place discussion and potential project for us hobby mechanics that are sitting around running out of past motorcycle races to stream. :teeth

So I have a couple of torque wrenches in my work shop and almost always reach for my beam type torque wrench over either of my clicker Craftsman ones.

If I had money to burn, I'd surely splurge on a Snap On, Mac, or similar high dollar tool... but like many of us.. I don't have that kinda of money to burn. Most of my frequently used tools are Craftsman, Motion Pro, or some of the old american made Thorsen wrenches. I fully understand the Craftsman tools aren't pro grade, but like to think they are a step up from Harbor Freight. That might be another SIP thread conversation.

So why do I go to my beam type torque wrench more often than not? I can visually see if its calibrated or not and its what I learned on. Simply have more trust in them.

So I started to think about the calibration of my ft lb clicker wrenches and possibly getting them calibrated. Understand its nearly $100 to have them professionally done... no bueno. Then I went down a rabbit hole reading and watching videos on the different DIY processes to calibrate.

Interesting different approaches from a digital torque converter, using a luggage scale, and finally hanging a weight off the wrench (and a little math of course.) I imagine the process is only as good as the digital torque converter purchased, and possibly the same using the luggage scale.

I do have a very accurate and verified mailing scale, which leads me to believe hanging a weight off my wrench (with a little math and measurement) might be the best process for me to attempt verification or even calibrate my clickers. Lots of articles and videos on this topic. Video below is just one of many.

Does anyone calibrate torque wrenches on their own? Thoughts on the process? Accurate enough to use on the In LB wrenches too? Being off a lb or two for on a 50 ft lb spec probably isn't as critical as being off the the same amount on a 7 or 8 ft lb bolt like cam caps (80 some in lbs.)

Thoughts?


youtu.be/1GrA5q_eu1k
 
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bikeama

bikeama

Super Moderator
Staff member
I have had my torque wrenches calibrated. I have a 1/4 inch Mossberg inch-pound dual-beam and a 1/2 inch Mossberg 250# dial. Both were spot on. My 3/8 inch Craftsman clicker was off 10%.

A good friend who is a gunsmith/gun manufacture has a test bench set up.
 
D

dmfdmf

Still A Rook
I call tools that *look* like a spring compressor, torque wrench, socket wrench, etc. (the Ideal form) but have some fatal design or material flaw and can't do the job or fail after one use a Platonic tool. Harbor Freight specializes in tools that fall into this category and I only buy them to save money if I really just need one use (fingers crossed!) out of some specialty tool that I will never need again. This gamble often pays off.

Craftsman used to be a good bet but when Sears was circling the drain I think they sold the brand to some venture company and they are now made of chinesium in Chy-nah (not racist) like everything else. The best place to get tools today is garage and estate sales. Estate sales are the best because usually the heirs are liquidating quality tools, bought decades ago, at fire sale prices.

I re-calibrate my beam torque wrench (ft-lbs) by gently bending the pointer back to zero. I do have an older Craftsman clicker (in-lbs) that still works but never calibrated it. It would probably be a good idea to calibrate it but that task is far down on my list even with the shutdown.

What the video failed to show was how do you calibrated the electronic doodad or the electronic weight scale that he used to calibrate the torque wrench. It is turtles all the way down. BTW, he made an error in advising not putting the weight on the center of the scale. The sensor to activate it is usually in the lower right corner but the best weight measurement is made with evenly distributed weight. Also it is best to calibrate a tool at roughly mid-range so, for example, my 200 in-lb Craftsman should be calibrated around 100 in-lbs. This will minimize the errors due to non-linearity across the full scale.
 
Starpower

Starpower

Well-known member
I too have a 40 y/o Craftsman beam that I usually reach for and 2 clickers that are used only when it is hard to read the beam scale. I have "calibrated" the clickers against the beam to end up getting the same results when checking a bolt and nut in a vise. Funky but the end result is good.
 
flips21

flips21

Serial Lurker
I purchased an AC Delco digital torque adapter which comes with its factory calibration test report. It is sold as being within 1.5% of true reading for less than $50 on Amazon. All three of my Harbor Freight sourced wrenches were better calibrated than my two Craftsman wrenches purchased long before Sears started circling the drain. All (5) were within 5% of the brand new AC Delco.

True, the AC Delco adapter could be off, but with all (5) wrenches being within 5%, that is good enough for any of my work.

Flip
 
dravnx

dravnx

Well-known member
I have half a dozen torque wrenches and tensiometers. The torque wrenches for work get cal'd yearly. The couple I have at home get cal'd every few years. I think it costs $35-40 per wrench. Not a real overhead when spread out over a couple of years.
 
gixxerjeff

gixxerjeff

Dogs best friend
dravnx said:
I have half a dozen torque wrenches and tensiometers. The torque wrenches for work get cal'd yearly. The couple I have at home get cal'd every few years. I think it costs $35-40 per wrench. Not a real overhead when spread out over a couple of years.
Click to expand...

^^^This^^^
My torque wrenches are all Snap-On....but this^^^
 
OaklandF4i

OaklandF4i

Darwin's exception
dravnx said:
I have half a dozen torque wrenches and tensiometers. The torque wrenches for work get cal'd yearly. The couple I have at home get cal'd every few years. I think it costs $35-40 per wrench. Not a real overhead when spread out over a couple of years.
Click to expand...

That really isnt a horrible price, less than I had heard. Where do you get it done? Is it local NorthBay?
 
dravnx

dravnx

Well-known member
This is who we use. $40/torque wrench. A couple of days turn around. Located in Rancho Cordova. We UPS them.
 
H

Heywood

Well-known member
I've used Team Torque in the past with good results. Pretty quick turn around seems to be within a few days of receiving it.
 
H

Heywood

Well-known member
dravnx said:
This is who we use. $40/torque wrench. A couple of days turn around. Located in Rancho Cordova. We UPS them.
Click to expand...

Who's in Rancho that you use? I work in RC and I rather just drop it off rather than ship it off to the midwest.
 
bergmen

bergmen

Well-known member
I made a crude fixture for checking accuracy and repeatability. Here are photos:
 

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dravnx

dravnx

Well-known member
A spring bathroom scale requires that the 4 corners all have the same weight that is then transferred to 2 bars that push on a fulcrum that drives a set of gears to the needle. Unless your center of force is exactly in the center and is pushing exactly perpendicular to the transfer bars, it will not be accurate. Then you have to overcome the gear lash, needle return spring force, etc. Just too much going on. Spend $40. Sheesh.
 
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