Normal for 70Nm to be difficult to pull on a 3/8" torque?
Discussion
I just opened a brand new teng 3/8" torque wrench and went to test it on some bolts. Underneath with not a great angle 70Nm was very difficult to pull and when tested on a wheel bolt it still required significantly more force than on my 1/2" one. It's 37cm long and my other 1/2" is 47cm long.
Obviously the length will make a difference to how much force is needed but should 10cm really make that much difference? I feel like my old one which hasn't been calibrated in years is way out.
Cheers
Obviously the length will make a difference to how much force is needed but should 10cm really make that much difference? I feel like my old one which hasn't been calibrated in years is way out.
Cheers
Baldchap said:
If a lever requires 100Nm to undo a bolt, increasing lever length by 1/3rd will require 75Nm to undo the same bolt.
Not sure about your units!To apply a force of 70Nm would need 19kg* at 47cm and 15kg at 37cm. So going from stiff to bloody awkward using one arm in a suboptimal position.
*Feel free to check my maths...
I decided to do a little test, not sure how accurate it is but i undid two wheel bolts, tightened one to a specific value with one wrench then one with the other wrench, then i swapped over wrenches and looked to see if the bolt moved at all before clicking. Tested on a number of torque settings and the bolt never moved at all when switching torque wrench.
I'm going to do the calibration test that people do with a vice and hanging weights. Again, not sure how accurate that will be but at least it should give me an idea if i need to start replacing bolts and re-torquing all the suspension work i did.
I'm going to do the calibration test that people do with a vice and hanging weights. Again, not sure how accurate that will be but at least it should give me an idea if i need to start replacing bolts and re-torquing all the suspension work i did.
Bill said:
Baldchap said:
If a lever requires 100Nm to undo a bolt, increasing lever length by 1/3rd will require 75Nm to undo the same bolt.
Not sure about your units!To apply a force of 70Nm would need 19kg* at 47cm and 15kg at 37cm. So going from stiff to bloody awkward using one arm in a suboptimal position.
*Feel free to check my maths...
king awfully. 
zaanztepS said:
I decided to do a little test, not sure how accurate it is but i undid two wheel bolts, tightened one to a specific value with one wrench then one with the other wrench, then i swapped over wrenches and looked to see if the bolt moved at all before clicking. Tested on a number of torque settings and the bolt never moved at all when switching torque wrench.
They're consistent with each other, so odds are they're fine. fwiw, recently I switched from a 3/8" to 1/2" torque wrench during a job for 60NM. 1/2" was easy, 3/8" was tricky.Some of the small wrenches have moulded handles that encourage you to hold it further up the bar.
There are loads of calibration videos on youtube https://www.youtube.com/watch?v=VrOvF9b5Qis
Its not hard. If you use weight lifting weights marked up with a value I'd recommend double checking it on a scale as they can be a fair bit out.
Its not hard. If you use weight lifting weights marked up with a value I'd recommend double checking it on a scale as they can be a fair bit out.
trickywoo said:
There are loads of calibration videos on youtube https://www.youtube.com/watch?v=VrOvF9b5Qis
Its not hard. If you use weight lifting weights marked up with a value I'd recommend double checking it on a scale as they can be a fair bit out.
Yeah, i've decided i'm going to try this. I thought you had to have a vice but of course all you need is to hang off a bolt somewhere. Its not hard. If you use weight lifting weights marked up with a value I'd recommend double checking it on a scale as they can be a fair bit out.
It would be interesting to see this method of calibration compared with the readings off one of those £1K plus calibration machines.
as mentioned, to apply a torque of 70Nm requires 149N of force with a 47cm lever, or 189N of force with a 37cm lever. so yes, 27% more effort needed with the shorter wrench.
a few years back a bought a 60cm long 'persuader' breaker bar - that would only require a force of 116N to get to 70Nm of torque. massive difference when compared to using a relatively tiny 4 way wheel wrench to undo overtightened wheel nuts!
a few years back a bought a 60cm long 'persuader' breaker bar - that would only require a force of 116N to get to 70Nm of torque. massive difference when compared to using a relatively tiny 4 way wheel wrench to undo overtightened wheel nuts!
It would seem nowhere in my house is flat enough for the scales to work accurately. My 10kg weights weigh either 9.5 or 11.2 according to my scales. The new and my old torque wrenches don't click when they should.
My Results:
New expected: 31.86Nm
New actual: 29Nm
Old expected: 43.3Nm
Old actual: 39Nm
The actual amount for both of them would be correct if the weight plates weigh 10.2Kg. Which they may or may not. At least it shows they are both very near each other in readings.
My Results:
New expected: 31.86Nm
New actual: 29Nm
Old expected: 43.3Nm
Old actual: 39Nm
The actual amount for both of them would be correct if the weight plates weigh 10.2Kg. Which they may or may not. At least it shows they are both very near each other in readings.
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