let's talk torque wrenches

Once I bought 'exotic' cars, I stepped up my tool game. Bought the best 1/2" torque wrench on the market. Proto Tools torque wrench. It's in the tool boxes of all the best techs in the industry. Best $300 ever spent.

Handles everything from the 78lb-ft of the titanium lugged 430's(don't go to 85!) to the 250 lb-ft of the center lug of a Porsche Cup Car and everything in between with perfection. Keeps the customers from griping about the $50/tire m&b charge when they see you 'hand torque' their lugs twice. You won't get that at Discount Tire! (You'll get a teenager with an air gun)

 

+1 for CDI, they make the Snap-on torque wrenches. CDI branded cost about half as much.

 

I will repeat that I have had excellent, long life and accurate results with Utica Tools. Holding calibration for decades.
Apex Tool Group

 

I have a bunch of different styles. I like to "see" the torque via the dial indicator ones if I can. I am also a fan of specific ranges for different needs. That is to say that I would not use a wrench with a range of 20-250 ft pounds for a 25 lb torque spec. I believe them to be most accurate in the middle of the range. Is this wrong?
Since we are talking torque wrenches...
I have heard that it is not correct to re-click the clicker-type again after the first click on the bolt. Is there any truth to this?

 

Does anybody know if there is a national chain that will calibrate clicker-type torque wrenches? I've been wanting to have mine calibrated for a while, but don't really want to ship them out.

 

Very cool -- will definitely pick one up.

 

No, that is not wrong --- best to be in the middle +/- 15% of the range.

No --- that is bunk.

 

Each successive one would ease to the click as the torque increased, as opposed to starting at the click tension. Just something I heard many years ago, this seemed like the place to bring it up.

 

Elastic modulus of steel does not change. Under threshold deformation use can be infinite. Physics baby....OK click on...

 

The dial type with the telltale pointer is my preference. I don't find them "wildly impractical" for working on cars, but you do need to keep an eye on the dial. And like any type of torque wrench, you need a bunch of different ones to cover different ranges.

Precision Instruments is the OEM for Snap-On's dial-type ("Torqometer") torque wrenches. They're exactly the same but for the printing on the dial. Years ago I ordered a 1% Torqometer. The Snap-On rep even mentioned that they were out-of-stock and it would have to be made to order by Precision Instruments.

Regardless, what we actually care about is fastener tension. We use torque as an indirect indicator of tension because bolt elongation is hard to measure. Dirty/rusty threads introduce more error into the torque/tension relationship than most wrenches do, so I wouldn't get too worried about that last percentage point or two.

 

While the first is clearly true, the second just sounds reasonable, but actually is not. Errors accumulate. This might result in lower total error, just as well as in increased total error, depending on the algebraic sign before the different errors.

So, one should generally get rid of all errors.

 

I torque to 80% first then again to 100%. I will use a second sequential click if the feel was not just right. Can't emphasize enough about fastener prep and the use or not of a lubricant and which type. Most torque specs are for dry fasteners in new condition unless otherwise noted. Lubricant may also be specified for internal engine fasteners. I have a set of Snap-on and Craftsman but the Craftsman's are really just used as long wrenches! Remember to use the correct scale!

I used to be concerned about accuracy of the wrenches until I saw a mechanic make short work of a front axel replacement. I asked him what torque he thought he tightened to and he said: "oh, pretty tight"! Unless your on the engine its really all in the feel.

 

Ah, yeah, those "feel"-experts. A few weeks ago a neighbor needed help with changing to winter wheels. The summer wheels (aluminium) hat been mounted just 2 months ago, so no issue of seizing. Not a strange back yard garage, but a renouned wheel service.

My professional impact wheel gun just got a few loose. For getting about half of the bolts loose, I had to instead use my "breaker", stand on it, and jump (I am no leightweight ). Yeah "pretty tight". Estimated torque: not less than 950 N (my weight) * 0,8 m (breaker length) = 760 Nm (disregarding the jumping). Should be not more than 120 Nm ...

 

This is true and it's not always obvious what is appropriate. For Ferrari 328 spark plugs, for example, the owners manual instructions are very specific:

From Owners Manual: "Prior to fitting the plugs make sure that their threads are lightly coated with graphite grease. If the sealing washer is new, first tighten to a maximum torque of 15 ft lbs, then slacken and retighten to 12 ft lbs"

 

It's about relative magnitudes. If thread condition is responsible for ten times as much error as the wrench, you will not materially alter the outcome by spending twice as much on a more accurate wrench.

 

Well, actually I admit that I never have fitted spark plugs with a torque wrench, but just by "feeling". They need rather little torque, as evidenced by your value of about 2 Nm and less, which is virtually nothing (almost). Is that correct? 1 Nm is 8.9 ft lbs? Then I usually have "overtorqued" presumably.

In case of the plugs it would seem even more important that the threads are clean and without any damage. For avoiding damage I press the top of the plug into a soft silicon hose and turn the other end of the silicon hose. If the plug threads in properly then you can turn it all the way in that way. If not, the hose will twist long before you are in danger of creating a burr.

OK, absolutely, that is right and simply means that at least the coarse grim and the burrs from the pliers should be removed .

 

It's worth bearing in mind that the calculation for torque is incredibly simple: lb/ft= amount of weight applied at the end of a lever of certain length. 100lb on the end of a 3' breaker bar = 300lb/ft of torque. Very useful when you are talking about really big torque eg the centerlock wheel of a Formula Atlantic car. The 3/4" torque wrench from snap on is $1K+, while a four foot breaker bar wielded by a personage of known weight, aided by some marking tape on the handle, yields identical results...

For extra credit, torque is a rough proxy for what really matters, clamping force of the joint. eg: stretch bolts used for certain heads don't care about torque, they care about the elasticity of the bolt material as a calculation of clamp force.

As discussed above, thread friction can dwarf other variables. Beware the 'fallacy of false precision'

 

Rats, I confused it with lbs in. 1 Nm is 0.74 lbs ft. I love those non-metric units .

That makes the plug torque value of 15 lbs ft correspond with 20 Nm. That sound more reasonable. I am quite sure that I stay below by "feeling" and that does not really matter. You can feel when deformation of the seal ring starts and when it ends. If the threads are OK.

 

Beru actually sells such a tool (tube?). I have one...cost all of $6 or so
BERU Spark Plug Assembly Aid, ZMH 001 | Federal-Mogul Global Aftermarket

 

The thing about spark plugs is that the plug wires keep them from turning.

 

But only if you secure the spark plug connector to the plug with a spark plug connector crimping device .

Amazing, and so cheap

 

The mechanic I referred to was a factory trained master mechanic with his own shop. I spent years in and out of Charlie's shop. When you do it for a living, you do a lot by feel. Same way you do your sparkplugs which I use just a small but consistent amount of aluminum anti-seize always leaving at least two threads dry before the ones that are exposed in the cylinder. -best

 

Indeed some guys (and girls) are good in that, but this implies to have the necessary "feel" and experience. Rather rare this, though. Definitely not the case with the tire shop I referred to .