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Originally Posted by Walt
If you hang a known weight a precise distance from the pivot of the torque wrench you'll get the same result. Just place a sacrificial bolt in your vice parallel to the floor, and place the wrench with appropriate size socket on the bolt head keeping it parallel to the floor. (X amount of pounds and Y amount of feet/inches/whatever) Alternately, use a hanging scale that you know to be accurate, and use it in place of the weight.

Make a mark on the wrench handle with pinstripe tape or similar and keep the weight on a string somewhere on your workbench, and check the calibration prior to use if you're concerned about it.


This is exactly how I calibrated my torque wrench last time. Does anyone have any issues with this technique?

Cheers,
Bill


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Interesting calibration idea, I wonder if one needs to allow for the weight of the torque wrench handle? It's probably insignificant though. Half a pound maybe on 10 foot pounds?


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I don't see anything wrong with that.


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Originally Posted by Hillbilly bike
..It attracted crazy women and rode to some wild times...
"Way back in the day"


Brilliant quote, and summed up my 1st Bonnie as well


















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Originally Posted by Walt
If you hang a known weight a precise distance from the pivot of the torque wrench you'll get the same result. Just place a sacrificial bolt in your vice parallel to the floor, and place the wrench with appropriate size socket on the bolt head keeping it parallel to the floor. (X amount of pounds and Y amount of feet/inches/whatever) Alternately, use a hanging scale that you know to be accurate, and use it in place of the weight.

Make a mark on the wrench handle with pinstripe tape or similar and keep the weight on a string somewhere on your workbench, and check the calibration prior to use if you're concerned about it.


Exactly what I did as well. To add on, for the known weight, I used plastic milk containers filled with a particular volume of water (8.34 pounds per gallon) as measured with a 1 qt. graduated cylinder for photographic development purposes. Found that my Harbor Freight torque wrench was accurate enough for my purposes. This wrench is rarely used so might be good enough. For a busy shop, maybe not.

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Originally Posted by HawaiianTiger
Originally Posted by Walt
If you hang a known weight a precise distance from the pivot of the torque wrench you'll get the same result. Just place a sacrificial bolt in your vice parallel to the floor, and place the wrench with appropriate size socket on the bolt head keeping it parallel to the floor. (X amount of pounds and Y amount of feet/inches/whatever) Alternately, use a hanging scale that you know to be accurate, and use it in place of the weight.

Make a mark on the wrench handle with pinstripe tape or similar and keep the weight on a string somewhere on your workbench, and check the calibration prior to use if you're concerned about it.


This is exactly how I calibrated my torque wrench last time. Does anyone have any issues with this technique?

Cheers,
Bill


The doubters here will say "how do you know the scale is accurate? How do you know the what was used to measure the string distance was accurate? grin


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Regarding calibration of a torque wrench, the weight of the handle when horizontal will contribute, and will have more impact at lower calibration weights.

You will choose your calibration weight to fall into the torque region that is of most concern to you. My guess for our interest is 15-25 ftlb for rods and head bolts.

So maybe calibrate at 20 ftlb.

This isn't actually pulling very hard, so if you're going to this trouble you can allow for the weight of the handle by weighing it on scales, as you would the small end of a rod.

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I'm sure the weight of the handle could be determined by the torque wrench itself. Providing it is not too far out of calibration.

We're just trying get in the ballpark, here, anyway. I under torqued a few heads myself before I took the trouble to calibrate my wrench. I didn't experience any problems because of that.

Cheers,
Bill



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Originally Posted by HawaiianTiger
I'm sure the weight of the handle could be determined by the torque wrench itself. Providing it is not too far out of calibration.

We're just trying get in the ballpark, here, anyway. I under torqued a few heads myself before I took the trouble to calibrate my wrench. I didn't experience any problems because of that.

Cheers,
Bill


I agree, "ballpark" is for the most part good enough. I firmly believe that an experienced hand can achieve the correct tension, or rather close enough, on most of our applications. I find it damned hard to get a torque wrench on a built up 3 piece crank for example.
The torque wrench is useful but not absolutely vital IMHO, I use them on cylinder heads and rod bolts, that's it. Torque wrench calibration may seem important, but it's far more important to ensure that all the Fasteners have a similar thread friction, ensuring equal tension on each fastener. A new lock nut will give a bit more friction, and therefore less bolt stretch, for the same amount of torque reading on the wrench.

http://www.boltscience.com/pages/tighten.htm

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i use beam-type torque wrenches exclusively, and have had excellent results lubricating the pivots with dundee marmalade.


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Too many people seem to have undue confidence in torque wrenches being able to tighten up the Fasteners correctly. That is not the case. If the end result is to put the right amount of stretch on the fastener, which translates to a clamping force, then there are things that count against torque wrenches. Thread lubricants and the size of the head are the main ones. There is an ASME standard for working out the correct torque for a given clamping force if anyone is troubled by insomnia.
Torque wrenches for the average mechanic are a lot better than not having one, but they are not the best for critical fastening. That is why many fastening directly measure bolt stretch, or do a rotational move after being nipped up.
But having said that, for the old British engines, there was probably so much overdesign that precise clamping force isn't a critical factor


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