Torque wrench question for anyone
 

I heard that due to the nature of a torque wrench, no matter how large or small the scale is, they are not very accurate in their lower end. The upper end of the wrench's scale is more accurate. Is that true??

probably true.for small torque values you can buy a smaller torque wrench.ive seen these used in auto tranny work.

Makes sense from a mathematical standpoint...

...if you could have an (imaginary) torque wrench with a range of 5 - 300 N/m, and the manufacturer claimed it was accurate to within 1/2 N, which critical torque value would you rather be off by 1/2N: the bolt requiring a mere 7 N/M, or the one requiring 200?

I would not expect my 1/2" drive torque wrench, that goes to 200 ft./lbs, to be accurate at 20-25 ft/lbs.
For the delicate jobs you would need a smaller ( 3/8" drive ? ), wrench, that may only read from 5 - 50 ft/lbs. ;)

torque wrench
 

Of what I have seen, most tool companies advertise 10% of the lower/higher end of the scale is not as accurate as the middle section. I have 3 of them to get the job done. They aren't cheap when you go with a high end brand.

Snap on sells torque wrenchs especialy made for the aircraft industry that are very accurate the also sell a tool to keep them calibrated both are expensive.It would be nice to have a set if you did a lot of tranny and engine rebuilding............

William Rogers..........

Is it true that beam type torque wrenches that Sears sells - those calibrated up to the 40 lb range for instance, are more accurate than the click type wrenches that are made for similar values.

I believe that for mechanical torque wrenches (as opposed to the newer electronic variety) you should not use the lower 20% of scale. Not sure about the electronic versions.

Gilly

i manufacture an engine component that really requires accurate torque for a proper installation.

we do not recommend the usage of "click-type" wrenches. we find that they are almost always out of calibration. furthermore, we find that the users of these wrenches think that the "click" is a torque limiter.

so, typically, they use these wrenches as if they are rowing for the harvard heavies. the "click"my be set to sound off at 60 ft lbs, but the moment of torque might go well beyond 100 ft lbs.

we recommend the balance beam style wrench. it arrests overtorque. it forces a more gentle impositon of torque.

we do not not recommend a "click" style wrench.

A point to remember when using a torque wrench is that the specified torque should be measured when the fastener is moving. So turn until you have the required torque and then stop - that way you don't get a false reading because of dealing with the static friction. What you shouldn't do is get close to the required torque, stop and then apply more torque, what you'll likely see is that you can reach the required torque WITHOUT the nut turning, that's because you're working against the static drag.

For the above reason IMHO the break type torque wrenches are easier to use.


Peter

So what do you experts recommend as a torque wrench for a shadetree like me?

You know, the type of guy that would probably do one or two head gasket projects in his lifetime, and maybe a few other related repairs that would require a torque wrench...

question (maybe dumb one)
 

just to clarify, by "click" type, are you guys talking about the kind where you set the torque at a value, and then when the torque is at that value, it clicks and then kind of breaks free so you are no longer applying any more torque?

Also, I'd always heard that torque wrenches are not that accurate at either the top or bottom ends of their scale, not just the bottom end. Also, most DIY torque wrenches (like mine) are probably way out of calibration from being dropped, failing to reset torque to 0 after each use, etc.

yes you're right
 

The other term is "sensory click". You set the limit on the wrench, when you reach that limit you can feel (in the handle) and hear a click. It does not break free at that point though, you could still keep pushing the limit hence tightening the fastener. I've never seen one of those-doesn't mean they don't exist, just that I've seen one.

I Have 1/2 and 3/8 Drive Torque wrenches and Send them out often for checking of calibration..
For Transmission work I use my Snap On 3/8 with the Dial and a light that lights up when correct value is reached...No Overtorque with that Torque wrench

Most Click Type Torque Wrenches will Over torque !

FWIW, one 1/2" drive & one 3/8" drive " click " style.
Torquing is such a fine art ( wet, dry, new fastener, used fastener, etc. ), not for a " Shady " to loose any sleep over. ;)