I use a 25 pound weight lifting weight and hang it from the wrench clamped in the vice. Set the wrench for 25 pounds and the weight will just make it click when hung. Then i know it is close.At least all the bolts will be even and equal.:-X12

 

>Is there such a thing as a way to calibrate or test the
>accuracy of a torque wrench? I am asking of course because
>I snapped a bolt off with my torque wrench set at 40 ft/lbs.
>last night. I had often wondered if the wrenches were
>accurate, but had never worried about it. This particular
>wrench is one that you set and it clicks when the desired
>torque has been achieved. The bolt I broke was actually one
>of the last bolts I tightened down, and the wrench seemed to
>work fine on the previous bolts.

 

RTV, or sliicone caulk is in it's uncured state a lubricant. Multiply any torque on a lubricated thread by at least 1.4 for carbon steel bolts or studs. I install large machinery and torque bolts often using a torque multiplier and torque wrench. When we torque them wet, lubricated, coarse threads, we use .6 the dry torque output value, plus a % for tool loss. Fine threads and other metals have different % of wet vs dry. Most automotive torque specs are for dry threads, easy to over torque wet.

Regards

 

I don't know about Snap-On, but Sears will re-calibrate their Craftsman torque wrenches for free once per year. Just an FYI. I got myself a set of Craftsman wrenches and take them in every year regardless.

 

>Get a good torque wrench, not
>one at Sears, an Armstrong, SnapON, Williams Ect.

Lots of good information here. Learning all the time.
OK, tell me what's wrong or whats not so good with my new torque wrench I just bought from Sears, just today in fact. I needed a new torque wrench to torque down the cylinder head bolts on my sons truck and my old Harbor Freight special was suspect, which was used to torque all the engine bolts in my old Ford Galaxie when I rebuilt it by the way. I don't need a torque wrench that often like some of you machanics do so I can understand why those of you who do this for a living would want to have a premium wrench in your top drawer. But will the Sears brand be ok for the home do it yourselfer? And I didn't know that Sears will re-calibrate it for free once a year. Thanks for the tip. So if that's true, then why wouldn't the Sears brand not be up to snuff? Thanks.

 

> I use a 25 pound weight lifting weight and hang it from
>the wrench clamped in the vice. Set the wrench for 25 pounds
>and the weight will just make it click when hung. Then i
>know it is close.At least all the bolts will be even and
>equal.:-X12

That's fine if the distance from the center of the square drive to the point where you hang the weight on the wrench is very close to 12 inches, and you keep the weight applied perpendicular to the wrench. If this is the case, you have a good functional check for your wrench. Most break action torque wrenches are at best +/-3% uncertainty(accuracy). A one inch difference is equal to just over 8% error! Slap that on top of the uncertainty of the wrench itself, and you're over a minimum of 11% potential error. If the distance is not 12 inches (lb/ft wrench), you can figure out the correct weight or distance easily. The angle is not as critical, if you keep it within about 15 degrees.

If the wrench is functioning properly, yet is not calibrated correctly, you will still get even and equal applied torque.

One thing I don't remember seeing mentioned is how fast you apply the torque to the fastener. With any TW, especially the break action (snap, click) type, you need to apply torque in a slow, steady motion. If you apply it quickly, or 'jerk' the wrench, you will not get reliable repeatable torque application to the fastener. Apply your motion too quickly and you tned to go beyond the 'click' and over torque as well. Dial and beam deflection type T wrenches are not as susceptable as you have to take the time to read these as you use them, and are not depending upon a mechanical mechanism to 'set' the wrench.

 

Jeez.... I carry a worn out, cheap torque wrench within arms leanth in my truck incase someone needs an attitude adjustment. I find that 50 ft pounds works well