I have a couple of click type torque wrenches ( 1/4" and 3/8") and have watched a lot of Youtube videos on testing their accuracy and calibration. I'm having a problem understanding the calibration logic. Specifically, the first measurement is made from the wrench head to a point on the handle. This point is marked on the handle and noted. Assuming that the wrench is starting out at it's lowest setting the mark/measurement will move and change as the handle is rotated to set the desired torque setting. My confusion is what 'good' is this first measurement in the formula TA = TS X (D1/D2)? Is it just a starting point? Why not take this first measurement after the wrench has been set to the desired torque setting? I'm missing something. Thank You for helping me understand.....I may be overthinking.
Click Type Torque Wrench Calibration Brain Cramp
- Thread starter JIMMIEM
- Start date
JohnDeere1
Banned
When sitting foot pounds they measure 12" on the torque wrench and they hang the weight from there foot pounds get multiplied per feet let's you you put 100 pounds on 2 feet that's 200 foot pounds at the end is this what's confusing?
cvairwerks
Well-known member
A quality designed torque wrench takes this into account if there is a significant change in length during setting. Most of the ones we use at work do not change lengths when adjusted. The set point also does not vary when changing head for different size fittings.
On the wrenches I have the entire handle moves when it is being set to the desired torque value. What is confusing me is taking a measurement before the handle is turned to set the torque value. This measurement would decrease as the handle is turned. Do all click style torque wrenches work like this or is the adjusting part of the wrench separate from the handle in which case setting torque would not move the handle?
Are you saying
1. Set wrench to 100 foot pounds
2. Mark spot 12 inches (1 foot) from center of ratchet
3. Hang 100 lb weight at the 12 inch (1 foot) spot
4. Wrench should click if it is accurate
Similar for the 200 foot pounds.
This part I get.....I don't get the calibration calculation logic.
Hmmmmmmm....I understand the calibration logic, but I don't know how to explain it. Many DIY calibration instructions suggest using a 20lb. weight. Don't confuse this with your 20lb. lowest setting. Toss those thoughts out.
You understand the concept that Torque (T) = Force (F) x Length (L)
Calibration is comparing the difference of actual torque applied vs. what the wrench displays as the "marked" torque. For simplicity, wrenches are usually calibrated with force applied at the center of the handle - the line shown on this wrench:
Lets go through the calibration procedure and calculation: http://www.wikihow.com/Calibrate-a-Torque-Wrench
(Actual) Torque Applied (TA) = Torque Setting (TS) x (Distance 1 (D1) / Distance 2 (D2) ).
For simplicity, lets assume the second picture above is 1 ft. from head center to handle center. Hang 20 lbs. on the handle center and it should click when set to 20 (D1). Instead, you turn the handle in and it clicks at 0.95 ft.(D2).
TA = 20 x (1.00'/0.95') = 21 ft. lb.
That .05' of difference equates to the wrench being 1 ft. lb. off in calibration when set at 20 ft. lb.
D1 is your starting reference. It can be anything....maybe 1.8 ft. on a certain wrench. Calibration is the difference between the wrench setting (D1) length AND the actual click point (D2) length.
Whew.......a very tough concept to explain. An equal force (i.e. 20 lb. weight) applied at different lengths = different torque applied. The logic is that you are comparing the differences of 20 lbs. applied at 1 foot (D1) vs. 0.95 ft. (D2).
You understand the concept that Torque (T) = Force (F) x Length (L)
Calibration is comparing the difference of actual torque applied vs. what the wrench displays as the "marked" torque. For simplicity, wrenches are usually calibrated with force applied at the center of the handle - the line shown on this wrench:
Lets go through the calibration procedure and calculation: http://www.wikihow.com/Calibrate-a-Torque-Wrench
(Actual) Torque Applied (TA) = Torque Setting (TS) x (Distance 1 (D1) / Distance 2 (D2) ).
For simplicity, lets assume the second picture above is 1 ft. from head center to handle center. Hang 20 lbs. on the handle center and it should click when set to 20 (D1). Instead, you turn the handle in and it clicks at 0.95 ft.(D2).
TA = 20 x (1.00'/0.95') = 21 ft. lb.
That .05' of difference equates to the wrench being 1 ft. lb. off in calibration when set at 20 ft. lb.
D1 is your starting reference. It can be anything....maybe 1.8 ft. on a certain wrench. Calibration is the difference between the wrench setting (D1) length AND the actual click point (D2) length.
Whew.......a very tough concept to explain. An equal force (i.e. 20 lb. weight) applied at different lengths = different torque applied. The logic is that you are comparing the differences of 20 lbs. applied at 1 foot (D1) vs. 0.95 ft. (D2).
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My brain hurts 
OP, what are you trying to do? Are you trying to calibrate one you already have? If so just got spend $20 and save the brain cells.
https://m.harborfreight.com/12-in-drive-digital-torque-adapter-68283.html
OP, what are you trying to do? Are you trying to calibrate one you already have? If so just got spend $20 and save the brain cells.
https://m.harborfreight.com/12-in-drive-digital-torque-adapter-68283.html
Last edited:
My brain hurts
OP, what are you trying to do? Are you trying to calibrate one you already have? If so just got spend $20 and save the brain cells.
https://m.harborfreight.com/12-in-drive-digital-torque-adapter-68283.html
I'm just trying to understand the logic. I understand the physics. What I'm trying to do is understand the calibration logic.
Hopefully Treeman's explanation will fix my brain cramp.
Hmmmmmmm....I understand the calibration logic, but I don't know how to explain it. Many DIY calibration instructions suggest using a 20lb. weight. Don't confuse this with your 20lb. lowest setting. Toss those thoughts out.
You understand the concept that Torque (T) = Force (F) x Length (L)
Calibration is comparing the difference of actual torque applied vs. what the wrench displays as the "marked" torque. For simplicity, wrenches are usually calibrated with force applied at the center of the handle - the line shown on this wrench:
Lets go through the calibration procedure and calculation: http://www.wikihow.com/Calibrate-a-Torque-Wrench
(Actual) Torque Applied (TA) = Torque Setting (TS) x (Distance 1 (D1) / Distance 2 (D2) ).
For simplicity, lets assume the second picture above is 1 ft. from head center to handle center. Hang 20 lbs. on the handle center and it should click when set to 20 (D1). Instead, you turn the handle in and it clicks at 0.95 ft.(D2).
TA = 20 x (1.00'/0.95') = 21 ft. lb.
That .05' of difference equates to the wrench being 1 ft. lb. off in calibration when set at 20 ft. lb.
D1 is your starting reference. It can be anything....maybe 1.8 ft. on a certain wrench. Calibration is the difference between the wrench setting (D1) length AND the actual click point (D2) length.
Whew.......a very tough concept to explain. An equal force (i.e. 20 lb. weight) applied at different lengths = different torque applied. The logic is that you are comparing the differences of 20 lbs. applied at 1 foot (D1) vs. 0.95 ft. (D2).
Is D1 the value that should be used to determine TS?
I see it kind of opposite. TS determines what D1 will be.
The TS (torque settings) are the scribed marks on the handle. When you crank your handle to 40 ft. lbs., you then set (determine) what D1 will be by measuring from head center to handle center.
When you hang a 40 lb. weight on the handle, you measure the length where it clicks (D2) and the difference vs D1 is how far off your calibration is.
I wish someone else could explain better. Any teachers here??
The TS (torque settings) are the scribed marks on the handle. When you crank your handle to 40 ft. lbs., you then set (determine) what D1 will be by measuring from head center to handle center.
When you hang a 40 lb. weight on the handle, you measure the length where it clicks (D2) and the difference vs D1 is how far off your calibration is.
I wish someone else could explain better. Any teachers here??
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