Torque Wrench

[chrisski]

Time for a new torque wrench!!

What recommendations? The ones I get on Amazon and Autozone are not working out. Mostly, under-reading a value and stripping out bolts.

For my solar installation, I'm looking at 1.5-12 NM (15-105 in/LBS). I would like a much broader range, but I'm sick of stripping bolts when torqueing to the proper setting, and would rather one that works.

[bob-n]

This is going to sound odd, but the Harbor Freight $10 torque wrenches are perfectly good. They won't last 20 years and will fail if you use them hard, but they are accurate and perfectly servicable for home use. When they do fail, it's typically a failure in the ratchet head.

A Harbor Freight torque wrench will have a coarser ratchet than a premium torque wrench. The steel isn't as carefully hardened or machined. It won't feel as nice or smooth in your hand. You get what you pay for, but it does the job accurately.

A while ago, I set up a torque wrench test station in my shop to test them. I clamp the square drive in a vice and hang weights on the handle until it clicks. I found that my 1/4" HF wrench is accurate for lower torques like we use in solar and my 3/8" and 1/2" HF wrenches are accurate for higher torques like tightening car lug nuts.

If you look at the knurled handle, you'll see that there is a narrow, smooth region in the center of the handle. This is important. I found that the weight must hang right on the smooth portion of the handle for accurate torque. I can't explain why, but it is true. If you hang an inch higher or lower on the handle, even accounting for the different length moment arm, you will get a pound or two of torque error. Also, that smooth groove is the location where your middle finger should go when you tighten the wrench, to get accurate torque. Don't just pull on the middle or far end.

I was told that even big-bucks torque wrenches are less accurate when pulled from the wrong location.

To keep it accurate, when the torque wrench is not in use, release all spring tension by dialing it to the lowest torque setting.

If you have a cheap torque wrench, you can get more confidence by testing it just before use. Use a vice to hold the square drive and position the wrench horizontally. Set it to your desired torque, calculate the right weight on the smooth band, then start hanging weights until it clicks. That way, you'll know that it is working.

I have no relation to HF and have no bias to one brand over another.

By the way, you mention that you're stripping bolts. That suggests that the wrench is applying MUCH more torque than desired, not just slightly more. There might be more to it than just a bad torque wrench. Some bolts are rated to be torqued dry. Adding anti-seize or oil to the bolt changes the torque. You must stop the instant that you get the first click. I've seen some people tighten to the click, back off, then tighten again. That's not typical manufacturer's recommendations for solar mountings.

In a typical solar install, stainless bolts hold aluminum rails to panels. If you tighten too much, you risk crushing the aluminum rail as well as damaging the bolt.

[bcroe]

Just a comment, I have seen amateur fitting tightening on Y tube, where one wrench is used and
all torque is transferred to the plumbing inside the AC unit. It should be done using a pair of
wrenches on opposite sides of the connection, opposed to absorb all torque, none transferred to
the machinery. Like same as tubes joined in space. Bruce Roe

[Mike90250]

If you are using smaller bolts, amazon has a gunsmiths torque wrench for the inch pounds & oz

[sdold]

Even if one has no feel for the proper torque, I've never heard of a wrench being so far out of cal that bolts break at the recommended torque. Are you using the wrench at close to the the bottom end of its torque range? Lubing them when the spec calls for dry threads, anything like that?

[chrisski]

Even if one has no feel for the proper torque, I've never heard of a wrench being so far out of cal that bolts break at the recommended torque. Are you using the wrench at close to the the bottom end of its torque range? Lubing them when the spec calls for dry threads, anything like that?

I guess I'm not actually ruining bolts, would have been better to say stripping the holes they go in and having to go back and tap and put helicoils. An example is my 20 year old car when I reinstalled the water pump, the aluminum bolt holes partially stripped out, and for that one I installed studs and that was a workaround to pulling the engine so I could get at the bolt hole with a tap in that little amount of space.

The other issue I have, is When I'm setting a torque value, if the wrench says 20, 30, 40, etc, and I need to set it to 30, the spin portion should read 0, but usually doesn't. This also gets me when I try to store these since I put it on 0, and it will be above or below the lowest setting.

Also did not know you could test these wrenches yourself with a vice.