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Using a torque wrench to loosen bolts

9

996GT2

Diamond Member
I've seen lots of conflicting opinions on this so I wanted to see what AT Garage thought of using a torque wrench to loosen a bolt. There are lots of people online who say it will damage the torque wrench, throw it out of calibration, etc., but I'm wondering...how does that work?

Say you have a bolt that's torqued to 30 ft-lbs. Maybe it's been on there for a few years and is a little rusty, so to loosen it, you now need to apply a 60 ft-lb force. So if you take a torque wrench and set it to 100 ft-lbs, why would it be damaged by removing a bolt which needed 60 ft-lbs to loosen?

And let's say that bolt was really rusted on and needed 120 ft-lbs to remove...wouldn't a torque wrench set to 100 ft-lbs click when you tried to loosen that bolt, thereby letting you know that you shouldn't apply more force and possibly damage the torque wrench?
 
Depends on the wrench. If it's a band or click style, and unneeded extra force can throw them out. I look at it this way, the tool has so many tighten cycles while it's in spec, why waste them on loosening a bolt when a breaker bar is cheap?
 
Really no conflict to me...?

Right tool for the job comes to mind and a torque wrench has its own job that it was designed for... Bolt or nut removal is not it...
 
I think there's a good chance you'll throw off the calibration if you do it. Go get yourself a breaker bar.

edit: Misread - if you apply more torque that needed than the bolt, but less than the max on the wrench you're good.
 
Breaker bars are dirt cheap. Good torque wrenches and calibration services are not. There is no way in hell I would ever use a torque wrench to remove a fastener.
 
It is such a foreign concept to me that I couldn't even tell you if a click-type even registers torque in that direction.
 
twinrider1 said:
It is such a foreign concept to me that I couldn't even tell you if a click-type even registers torque in that direction.
Click to expand...

It does. It has a selector for directions, just like a normal ratcheting wrench.

I'm not saying that I plan to use a torque wrench to loosen bolts in place of a breaker bar, but I just don't understand why it's bad for the torque wrench if you set it to say, 150 ft-lbs and use it to loosen a bolt that only needs 50 or 100 ft-lbs to come loose. I mean, isn't it technically impossible to put too much strain on the torque wrench since it'll click at 150 if the bolt needs more than that much force to come loose?
 
Irrelevant if it's bad or not, question is why would you use one to break tightened nuts? Like was said before, a torque wrench has just so many cycles of tightening before its calibration is lost, so why shorten that period by breaking nuts loose?
 
The better question is WHY are you loosening bolts with a torque wrench? Is there a specific purpose like you're trying to see how much force is holding on a bolt or are you doing this out of being lazy? If you're going to do this, do this with a split-beam torque wrench, never with those "clicky" type torque wrenches because those require constant re-calibration and are a pain in the ass to maintain while a split-beam requires no such thing so long as the dial lines up. Yes if you use a split-beam torque wrench up to its limit, and you don't bang your hand on it, it shouldn't destroy it but I just wouldn't use this to remove bolts unless it's super important to you to find out how heavily torqued down those bolts are.
 
As others have said, there is no reason to need to use a torque wrench to loosen a bolt or nut. What is important is the torque value and sequence when you put something like an engine head back on the block. Once you take something off, you can easily tell what failed and most times, why. If for example a head gasket blows, you or the machine shop always checks for head warping and cracks, before it goes back on. Knowing how tight the other mechanic made the bolts is useless and a lot of engine bolts, mainly heads and rod bolts, now are Torque To Yield and can not be reused.
 
996GT2 said:
It does. It has a selector for directions, just like a normal ratcheting wrench.

I'm not saying that I plan to use a torque wrench to loosen bolts in place of a breaker bar, but I just don't understand why it's bad for the torque wrench if you set it to say, 150 ft-lbs and use it to loosen a bolt that only needs 50 or 100 ft-lbs to come loose. I mean, isn't it technically impossible to put too much strain on the torque wrench since it'll click at 150 if the bolt needs more than that much force to come loose?
Click to expand...

I wouldn't say it bad, bu as I said earlier it depends on the type of wrench. Beam style? No harm no foul there really. If you have to set it though, the tighter those bands are the less accurate and more stress you put on the internals thus affecting the calibration. With breaker bars being so cheap, why bother?
 
My guess is when you break a bolt free you quickly go from very high torque to very low torque, so you put a large shock on the wrench. Whereas when you are tightening bolts the torque will slowly and continuously ramp up, so there is no shock on the mechanism.

In aircraft maintenance you have to torque check critical fasteners from time to time and it is always done in the tightening direction. If a mechanic thinks a fastener is too tight they will back it off with a normal wrench and the retighten with the torque wrench.
 
Agree with people asking 'why?' because a regular ratchet, breaker, or wrench will work just fine. If you need a little more torque, hit it with a hammer. If you need a lot of torque, get an impact gun.
 
Most of the torque wrenches "work" in only one direction. It may have a lever to change the direction but the chances are, it will not "click" in the wrong direction. I have seen few which do but it is rare.

Assuming the mechanism is designed to work only that direction, putting torque in the opposite direction is going cause the wrench to go off calibration.
 
sontakke said:
Most of the torque wrenches "work" in only one direction. It may have a lever to change the direction but the chances are, it will not "click" in the wrong direction. I have seen few which do but it is rare.

Assuming the mechanism is designed to work only that direction, putting torque in the opposite direction is going cause the wrench to go off calibration.
Click to expand...

What's the point of the lever then?
 
sontakke said:
Most of the torque wrenches "work" in only one direction. It may have a lever to change the direction but the chances are, it will not "click" in the wrong direction. I have seen few which do but it is rare.

Assuming the mechanism is designed to work only that direction, putting torque in the opposite direction is going cause the wrench to go off calibration.
Click to expand...

This is not true. Most torque wrenches will work in either direction. This is necessary because some fasteners used in engine manufacturing are reverse threaded so they will not loosen while the engine is running and torque settings are critical in engine manufacturing.

If your torque wrench doesn't work in both directions there is something wrong with it or you bought a piece of crap torque wrench (I have heard this complaint regarding harbor freight brand torque wrenches).

I just bought a good quality torque wrench and it came with calibration certificate for both directions. It is slightly more accurate turning clockwise but it will measure torque turning counterclockwise as well.
 
996GT2 said:
It does. It has a selector for directions, just like a normal ratcheting wrench.

I'm not saying that I plan to use a torque wrench to loosen bolts in place of a breaker bar, but I just don't understand why it's bad for the torque wrench if you set it to say, 150 ft-lbs and use it to loosen a bolt that only needs 50 or 100 ft-lbs to come loose. I mean, isn't it technically impossible to put too much strain on the torque wrench since it'll click at 150 if the bolt needs more than that much force to come loose?
Click to expand...

By the way, some fasteners in an engine might have thread locking compound on them when tightened so when you go to loosen it, even though it was torqued to a specific number, it might take way more torque to loosen than it was originally tightened to because of the thread lock compound.
 
JulesMaximus said:
This is not true. Most torque wrenches will work in either direction. This is necessary because some fasteners used in engine manufacturing are reverse threaded so they will not loosen while the engine is running and torque settings are critical in engine manufacturing.

If your torque wrench doesn't work in both directions there is something wrong with it or you bought a piece of crap torque wrench (I have heard this complaint regarding harbor freight brand torque wrenches).

I just bought a good quality torque wrench and it came with calibration certificate for both directions. It is slightly more accurate turning clockwise but it will measure torque turning counterclockwise as well.
Click to expand...

I love this argument. My HF torque wrench is more accurate than my snap on and it works in both directions!! Magic!
 
Gillbot said:
I love this argument. My HF torque wrench is more accurate than my snap on and it works in both directions!! Magic!
Click to expand...

Comments about Pittsburgh Professional 3/4" Drive Click Type Torque Wrench:
Tested against electronic torque tester. Was +/- 1 ft-lb all the way up to 300 ft-lb. Does not click in the counterclockwise direction at all. Not sure why it is advertised to do so. Otherwise, awesome tool for the money.
Click to expand...

Comments about Pittsburgh Professional 3/4" Drive Click Type Torque Wrench:
I thought everything was great, when I torqued the passenger side wheel hub nut on the vehicle (normal right hand threads)... ...when I went to the driver side (left hand threads) I found out the hard way that it didn't click at all in the counter-clockwise direction, despite the wrench having "6%+- tolerance" on the CCW direction. I took it back, and got another. Yep, same deal - IT DOESN'T WORK COUNTER CLOCKWISE.
Click to expand...

All I know is the HF torque wrench I bought did not come with a calibration certificate and the CDI torque wrench I just bought did. I feel more confident in the CDI torque wrench.
 
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