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  #1  
Old 01-07-2012, 10:33 AM
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Location: Barrington, RI
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A Cheapskate Calibrates His Torque Wrench

Given (a) I only wanted to buy a cheap torque wrench and (b) I live in fear that a cheap torque wrench will get me into trouble (as it did several years ago when I snapped an oil filter canister bolt ), I found an easy way to make sure my wrench is basically within spec. You more experienced types will know all this, but for novices like me this may prove helpful.

I was inspired by the following video: How to Check the Calibration Accuracy of Your Torque Wrench (Video 2) - YouTube

Since I don't even own a vise, I did the following:

1. Got a bolt with a 1/2" head (the largest one that my 1/4" wrench would fit) and tightened it as tightly as I possibly could into some metal shelving (i.e. far tighter than any of the torque values on my wrench).

2. Got a 5 lb. and 10 lb. dumbbell and weighed them exactly on a digital scale.

3. Measuring 9" from the center of the wrench head and using the weights individually and in combination, I came up with torque values of 45, 92, and 137 in-lbs., covering the mid-range of the wrench which is 20-200.

4. Then, hanging the weights with wire from the 9" point on the wrench handle, I was able to confirm that the wrench is within spec.

Kind of fun to do and gives me peace of mind.
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06 E320 CDI "Benson", Platinum Blue, 176k mi
06 E320 CDI "Rutherford", Black, 146k mi
91 300D "Otis", Smoke Silver, 129k mi
98 E300 "Murray", Silver, 129k mi, Stage 2 Rocketchip chip tuned, under son's care, getting EXPENSIVE!

Twelve other MB's owned and sold
2002 Honda Odyssey 255k mi (want to name it "Homer," wife won't let me)
1961 Very Tolerant Wife
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  #2  
Old 01-07-2012, 11:38 AM
Shadetree
 
Join Date: Jan 2010
Location: Back in SC upstate
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No, a real cheapskate borrows a good one. :)

Did you get your wrench level? Seems if it was perpendicular to plumb your theory would gain traction.

I enjoyed your exercise.
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  #3  
Old 01-07-2012, 12:02 PM
Diesel911's Avatar
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Your description is how they actually used to calibrate Torque Wrenches back in the Old Days.
I saw a picture in a very old Auto Mechanics book of them doing the same.
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  #4  
Old 01-07-2012, 12:05 PM
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Quote:
Originally Posted by Clemson88 View Post
Did you get your wrench level? Seems if it was perpendicular to plumb your theory would gain traction.

I enjoyed your exercise.
Yes, wrench needs to be perfectly horizontal.
__________________
06 E320 CDI "Benson", Platinum Blue, 176k mi
06 E320 CDI "Rutherford", Black, 146k mi
91 300D "Otis", Smoke Silver, 129k mi
98 E300 "Murray", Silver, 129k mi, Stage 2 Rocketchip chip tuned, under son's care, getting EXPENSIVE!

Twelve other MB's owned and sold
2002 Honda Odyssey 255k mi (want to name it "Homer," wife won't let me)
1961 Very Tolerant Wife
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  #5  
Old 01-07-2012, 12:38 PM
DeliveryValve's Avatar
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Join Date: Jun 2006
Location: Central California
Posts: 4,117
I use a Digital Torque Adapter. Not a cheap way of finding out how accurate your torque wrench is but it is an effective way.

My digital torque adapter is a Powerbuilt drive unit from ALLTRADE tools based in Long Beach, CA. The calibration inspection paper of my unit states the most error it has is .3% (point three percent).

Powerbuilt Digital Torque Adapter - YouTube

I only use it to check out my torque wrenches. When I tested my buddy's cheap Harbor Freight Clicker torque wrench. At the setting of 50 ft-lbs, the torque adapter noted 53.4 for an error of 6.8% . At the setting of 80 ft-lbs the torque adapter noted 71.3 ft-lbs for an error of -10.88%. Needless to say, the torque wrench went to the garbage.



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  #6  
Old 01-07-2012, 12:48 PM
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Quote:
Originally Posted by DeliveryValve View Post
I use a Digital Torque Adapter. Not a cheap way of finding out how accurate your torque wrench is but it is an effective way.

My digital torque adapter is a Powerbuilt drive unit from ALLTRADE tools based in Long Beach, CA. The calibration inspection paper of my unit states the most error it has is .3% (point three percent).

Powerbuilt Digital Torque Adapter - YouTube

I only use it to check out my torque wrenches. When I tested my buddy's cheap Harbor Freight Clicker torque wrench. At the setting of 50 ft-lbs, the torque adapter noted 53.4 for an error of 6.8% . At the setting of 80 ft-lbs the torque adapter noted 71.3 ft-lbs for an error of -10.88%. Needless to say, the torque wrench went to the garbage.



.
That's pretty cool. 1/2" version available on Amazon for less than $40.
__________________
06 E320 CDI "Benson", Platinum Blue, 176k mi
06 E320 CDI "Rutherford", Black, 146k mi
91 300D "Otis", Smoke Silver, 129k mi
98 E300 "Murray", Silver, 129k mi, Stage 2 Rocketchip chip tuned, under son's care, getting EXPENSIVE!

Twelve other MB's owned and sold
2002 Honda Odyssey 255k mi (want to name it "Homer," wife won't let me)
1961 Very Tolerant Wife
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  #7  
Old 01-07-2012, 01:04 PM
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Quote:
Originally Posted by shertex View Post
Thumbs up to Shertex but the video is terrible.

38 seconds in he says "Torque is equal to length times width." Isn't that area? About 50 seconds in he says it again.

Then he says if it clicks when you hang the weight you're good. That could mean it's reading low. You should find the exact setting at which the reference torque registers, as Shertex did.

I'm not keen on the soft jaws on his bench vice, which he calls vice grips, either.

Sixto
87 300D
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  #8  
Old 01-07-2012, 01:11 PM
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Quote:
Originally Posted by sixto View Post
Thumbs up to Shertex but the video is terrible.

38 seconds in he says "Torque is equal to length times width." Isn't that area? About 50 seconds in he says it again.

Then he says if it clicks when you hang the weight you're good. That could mean it's reading low. You should find the exact setting at which the reference torque registers, as Shertex did.

I'm not keen on the soft jaws on his bench vice, which he calls vice grips, either.

Sixto
87 300D
He means weight, not width. Sometimes he says weight, sometimes width.
__________________
06 E320 CDI "Benson", Platinum Blue, 176k mi
06 E320 CDI "Rutherford", Black, 146k mi
91 300D "Otis", Smoke Silver, 129k mi
98 E300 "Murray", Silver, 129k mi, Stage 2 Rocketchip chip tuned, under son's care, getting EXPENSIVE!

Twelve other MB's owned and sold
2002 Honda Odyssey 255k mi (want to name it "Homer," wife won't let me)
1961 Very Tolerant Wife
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