TQ wrench recalibrations
07-30-2003, 03:52 PM
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TQ wrench recalibrations
I had no idea where to put this so I'm gonna post it here. Maybe a new forum for "tools" might be in order...but I don't know if it would get enough traffic. Anyway to my situation. I just got my shortblock less week and most everything else to bolt onto is here. I just spend a lot of money on everything so I wanna make sure it goes together properly the first time (mainly heads and intake bolts) The TQ wrench that I have is a 3/8 drive that I got from Sears about a year ago. I really haven't used it all that much..probably just about bolting on a couple set of heads, intakes and a few other things. Everytime I've used it, I've always set it back to zero like it should be. Now that most of the background it out of the way...I guess my real question is, what does it take for a TQ wrench to loss calibration? Like what kind time and/or usage? I called my local machine shop today and they said that MAC does them for 100 bucks which or more then I payed for it in the first place. I mean I could just go buy another one for like $60 but I really don't want to if I don't have to. Anyone got any creative idea on how I might go about testing it? Any input would be great guys.
Thanks again,
Tom
Thanks again,
Tom
07-30-2003, 04:06 PM
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Well, I would have to say that I can help you in that area. As you probably already know I am in the US Air Force and my job is exactly that, calibrating test equipment, to include torque wrenches.
It is very good that you stored it at the 0 reading, that action alone probably saved you the $100 dollar recalibration fee and the price of a new torque wrench.
The only way to truely check it is to have it calibrated, but, from my experience (I have calibrated well over 1000 wrenches), the only time a torque wrench losses its accuracy is when it is dropped, stored in extreme climates, stored when set at something othere than zero, or used multiple times a day throughout the corse of a year.
It sounds like you have taken very good care of your wrench and judging by what you have told me, it should still be as accurate as the day you bought it. On the other hand, a $100 recalibration fee is cheap insurance to ensure that your wrench still meets its rated accuracy.
One last thought for you; just because you buy something new doesn't mean that it is as accurate as it says it is. When I recieve a wrench that someone has bought brand new, more than half the time it needs to be adjusted to achieve its rated accuracy.
I hope this helps
Good luck with the engine!!!
It is very good that you stored it at the 0 reading, that action alone probably saved you the $100 dollar recalibration fee and the price of a new torque wrench.
The only way to truely check it is to have it calibrated, but, from my experience (I have calibrated well over 1000 wrenches), the only time a torque wrench losses its accuracy is when it is dropped, stored in extreme climates, stored when set at something othere than zero, or used multiple times a day throughout the corse of a year.
It sounds like you have taken very good care of your wrench and judging by what you have told me, it should still be as accurate as the day you bought it. On the other hand, a $100 recalibration fee is cheap insurance to ensure that your wrench still meets its rated accuracy.
One last thought for you; just because you buy something new doesn't mean that it is as accurate as it says it is. When I recieve a wrench that someone has bought brand new, more than half the time it needs to be adjusted to achieve its rated accuracy.
I hope this helps
Good luck with the engine!!!
07-30-2003, 04:18 PM
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Hey thanks for all the great info. I have heard of TQ wrenches not being accurate right out of the box like you mentioned. That, besides the cost is the other reason I wasn't quick to rush out and get a new one cause for all I know, it might be not exactly accurate also. But, when it comes to new wrenches not being right on spec out of the box....what kinda variance are we talking about? Like a tiny bit, a little bit, or way off? But hey, thanks for all the great info so far.
Tom
Tom
07-30-2003, 04:24 PM
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The definition of torque is
Force X Distance
or Force cross product Distance
or Force times Distance times the cosine of the angle of the applied force.
With that in mind, put a 3/4" deep well on your torque wrench and put it on a lug nut of a wheel. Make sure that the wrench is at the ~2 o'clock position so that when the wrench is loaded, it will be in the 3 o'clock position.
Using a coat hanger, loop it around the end of the torque wrench and threw some barbell weights. Measure the length between the center of the drive of the wrench and coat hanger. Since the wrench is parallel to flat ground, calculate the torque applied to the wrench. Then "range" the adjuster to see where the wrench clicks at.
Example, say I use 50 pounds of weight and I measure 17 1/2" between center of the drive of the wrench and coat hanger.
So 50 * 17.5 = 875 in-lbs, and there are 12 in-lbs in 1 ft-lbs, so there is 73 ft-lbs of torque applied to the wrench.
Set the wrench to 67 ft-lbs and test for the click, it should.
Set the wrench to 73 ft-lbs and test for the click, it should.
Set the wrench to 78 ft-lbs and test for the click, it SHOULD NOT!
You can fine tune the setting to even closer. And also try different weights like 25 pounds and 75 pounds.
If the torque wrench is out of calibration, get a new one.
If you ever drop a torque wrench, assume that it is BIG TIME out of calibration. Wonder how many rod bolts have been distorted due to a faulty torque wrench. Hmmmmm....
Force X Distance
or Force cross product Distance
or Force times Distance times the cosine of the angle of the applied force.
With that in mind, put a 3/4" deep well on your torque wrench and put it on a lug nut of a wheel. Make sure that the wrench is at the ~2 o'clock position so that when the wrench is loaded, it will be in the 3 o'clock position.
Using a coat hanger, loop it around the end of the torque wrench and threw some barbell weights. Measure the length between the center of the drive of the wrench and coat hanger. Since the wrench is parallel to flat ground, calculate the torque applied to the wrench. Then "range" the adjuster to see where the wrench clicks at.
Example, say I use 50 pounds of weight and I measure 17 1/2" between center of the drive of the wrench and coat hanger.
So 50 * 17.5 = 875 in-lbs, and there are 12 in-lbs in 1 ft-lbs, so there is 73 ft-lbs of torque applied to the wrench.
Set the wrench to 67 ft-lbs and test for the click, it should.
Set the wrench to 73 ft-lbs and test for the click, it should.
Set the wrench to 78 ft-lbs and test for the click, it SHOULD NOT!
You can fine tune the setting to even closer. And also try different weights like 25 pounds and 75 pounds.
If the torque wrench is out of calibration, get a new one.
If you ever drop a torque wrench, assume that it is BIG TIME out of calibration. Wonder how many rod bolts have been distorted due to a faulty torque wrench. Hmmmmm....
07-30-2003, 04:43 PM
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Once you get one of these, you never use a click type of torque wrench ever again (at least I won't!). One can re-zero the wrench and its way easier to check the calibration on it.
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07-30-2003, 11:19 PM
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In responce to the other posts here:
a73camaro is right about the math involving torque but you will only be able to achieve the right results (within your TQ wrench accuracy) if you use the right technique. Be sure that you have nothing but right angles...anything else will introduce what is called cosign error, which a73camaro touched on briefly. Most likely, with that proceedure, you will get a rough idea if the TQ wrench needs recalibration or not; you definately will not achieve the accuracy that a professional metrology laboratory will achieve.
The dial indicating type TQ wrenches (as pictured above) are very good but it really comes down to preference. Almost all companies that make a dial indicating TQ wrench, make a snap action wrench that is just as accurate. I personally would go with snap action because if you do drop it, you can always have it checked and adjusted back to its rated accuracy (which isn't hard by the way); a dial indicating wrench can not be adjusted very easily so for the most part, when it is worn out, old, or broken, it's basically trash. They are the ideal wrench to use when checking run down torque (backwards torque).
As far as wrenches being "off" from the manufacturer; they usually are only a fraction out of their rated accuracy, but that is still way off of what they should be. Average accuracy wrenches from snap-on are +or- 4% of indication; typically they pass that accuracy but sometimes they only pass 4.5%-5%.
Like I said before, Recalibration is a small price to pay to ensure your engine is properly torqued.
a73camaro is right about the math involving torque but you will only be able to achieve the right results (within your TQ wrench accuracy) if you use the right technique. Be sure that you have nothing but right angles...anything else will introduce what is called cosign error, which a73camaro touched on briefly. Most likely, with that proceedure, you will get a rough idea if the TQ wrench needs recalibration or not; you definately will not achieve the accuracy that a professional metrology laboratory will achieve.
The dial indicating type TQ wrenches (as pictured above) are very good but it really comes down to preference. Almost all companies that make a dial indicating TQ wrench, make a snap action wrench that is just as accurate. I personally would go with snap action because if you do drop it, you can always have it checked and adjusted back to its rated accuracy (which isn't hard by the way); a dial indicating wrench can not be adjusted very easily so for the most part, when it is worn out, old, or broken, it's basically trash. They are the ideal wrench to use when checking run down torque (backwards torque).
As far as wrenches being "off" from the manufacturer; they usually are only a fraction out of their rated accuracy, but that is still way off of what they should be. Average accuracy wrenches from snap-on are +or- 4% of indication; typically they pass that accuracy but sometimes they only pass 4.5%-5%.
Like I said before, Recalibration is a small price to pay to ensure your engine is properly torqued.
07-31-2003, 05:20 AM
#9
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a73 camaro, i have 2 of the dial type wrenchs and only use them for checking bearing preload. have 2 with the little thumb wheel on the side, those are my preferd torque wrenchs, plus i have 2 of the micro adjust types i seldom use.
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