# A “torque wrench” or a “wrench”?

Could "wrench" mean something different from a torque wrench?

Would the meaning here be vague if I left off the word "torque" in the following passage?

The biggest difficulty in giving instructions is, as already noted, over-estimating what your audience already knows. Telling someone to remove a part on their car using a torque wrench doesn’t help much if they don’t know how to use a torque wrench, or even what one is. Problems can also arise when you fail to adequately describe a point — it often is not clear until several steps later that a failure has occurred, and the only thing to do for it is to trace your steps backwards until you find the error.

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For an informal usage as you seem to have written in your example, I would say it doesn't matter.

A torque wrench is different from a wrench, however, so if you were using it in a more formal sense, like a training manual, I would specify the difference.

Apparently, a torque wrench has a gauge on it that measures how much torque you have applied to the bolt you are fastening, and thus it is important in cases where the tightness of the bolt needs to be precise.

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I mildly disagree; it does matter somewhat in this example that the more precise "torque wrench" is being used rather than "wrench," because the example is all about mistaken assumptions. – user1579 Apr 18 '11 at 16:32
@Rhodri True, good point, but remember that the car part is being removed and you wouldn't need a torque wrench for that, only for tightening. One could substitute in "monkey wrench" or "socket wrench" if they wanted to be retain the possibility of a mistaken assumption. – gbutters Apr 18 '11 at 16:50
One could, but one would have to. With just "wrench" you are working with a different type of mistaken assumption. – user1579 Apr 18 '11 at 17:01

In my experience, which agrees with wikipedia "torque wrench" means a wrench which gives a controllable torque, either through measurement of the torque applied or due to a mechanism which prevents a torque greater than a given amount. So a torque wrench is a subset of the set of wrenches.

On the other hand, the noun "wrench" applies to things other than tools. See the Free dictionary definition of wrench.

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A Wrench (spanner in BE) is to tighten or loosen a nut

A torque wrench is used to finally tighten a bolt to the correct tension.

It either has a scale (analog or digital) or a clutch that is set to release at a certain torque.
Note: you wouldn't use a torque wrench to remove a nut - that's the point in the article.

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@mgb - Thanks for the pictures. – brilliant Apr 18 '11 at 0:51
@brilliant - in a strictly physics sense 'torque' is redundant, what else does a wrench do, but in reality or engineering they are different things. – mgb Apr 18 '11 at 0:58
@mgb: True, a torque wrench wouldn't be used to remove a nut, but I don't think that's the point in the question's quote. It seems to me it is rather a mistake in the quote, since it should say tighten a nut, and the whole reason for mentioning the torque wrench is to serve as an example to communicate the main point of the paragraph. – mgkrebbs Apr 18 '11 at 4:54
I thought "telling someone to remove a part using a torque wrench" was a double irony. They wouldn't know what a torque wrench was or why removing a part with one was wrong. – mgb Apr 18 '11 at 4:58
Also, "wrench" in the UK will commonly be used to refer to a socket wrench, or an adjustable wrench (no "socket spanners", or "adjustable spanners"). – Marcin Apr 18 '11 at 16:30

A torque wrench provides a gauge or other indicator to show how many foot-pounds of pressure are being applied. This measure is important for things that must bind within a certain tolerance, like two pieces of a motor engine's casing. Too light a pressure, and it won't form a seal; too much pressure, and you may crack the sealing layer, or worse, the metal around the bolt hole.

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It's important to use a torque wrench to install automotive spark plugs. If you over-tighten a plug, you can break the plug, or strip the threads on the plug and/or engine block. Repairing that can be very expensive and may even require a new engine. Someone once tried to sabotage my car by tightening the spark plugs with an impact wrench, which delivers far too much torque; I was lucky he didn't succeed. – Bob Murphy Apr 18 '11 at 5:55

There's a tip for you. When I want to learn about a technical word, I search the word in Google Images. As you can see, clearly there is a difference between normal wrench and torque wrench. A picture values a thousand words.

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Thank you. I'll be doing it from now on. – brilliant Apr 18 '11 at 20:01