Mechanics: what are your most common tools?

Those 90 and 45 degree instructions aren't hair-splitting critical. If you're within 5 degrees you're good?

Snap-On publishes their torque wrench limits of accuracy. They seem pretty good, and their disclosure is thorough.

No tool is 100 percent accurate; it's sophomoric to think otherwise.

 

I'm attaching the calibration page that came with it for your reference in case anyone else is interested in getting one. One thing I did not know from the descriptions, is that yes, it does do 4 Nm AND 90 degrees. All the descriptions show that it does torque, and it does angle, but not both one after the other/at the same time. This is exactly what I was looking for. Although after reading the page carefully you have to rotate the arm at a certain speed for the accuracy to be true. Not sure I can accomplish the given speed......

I don't want to shear an aluminum bolt head on top of a magnesium part. The magnesium is flammable so I'm not sure it's safe to drill the bolt out....

 

The angle measurement is (sure to be) done with a gyroscope. So the "certain speed" is just a broad suggestion so that the gyro reads accurately as you move the wrench. Slow + steady is probably all that is really needed. You can probably do some experiments to confirm, on different fasteners that aren't so delicate.

And I would not worry about the magnesium fire. It burns very hot, and is difficult to put out, which is why it is so well known. But it's pretty hard to get started. Back in the day I worked at a place using high speed machining (20k+ RPM) of magnesium parts, so it was a concern, but very rare event.

 

The inexpensive wrenches from Harbor Freight are all $19.99; 1/4 in.drive, 3/8 in.drive and 1/2 in.drive. They are not what I have or use now ... but if I was in the market they would be my purchase.

I think sometimes some of you guys go a little bit overboard on the nit-pickiness aspect of things. But then again ... I guess everyone should be able to get what they like.

 

I agree, here in America, people CAN get what they want. If they have the money that is.
AND, some people are TOO nit picky!

I worked at dealerships. Cheap tools don't last! If you only use then once in a while, you'll probably
be fine.
Specialty tool are different. I would guess cheap torque wrenches are more or less accurate, close enough.
And good enough more most jobs. But how LONG do they stay accurate? If you under torque the head bolts, the head gasket could leak, and/or the risk of the head warping goes up. The same could be true if you over torque them. The bolt could
brake, or strip the threads. Then you'll need a new engine, or spend a lot of money to get it repaired.

I'm not saying everyone should go out and but Snap On tools.
A good rule of thumb would be get the best YOU can afford.

 

Even a Snap-On is expected to get a professional recalibration every year (or 5,000 clicks, if that happens sooner).

Right, I don't either.

I suspect if I were to take my old Craftsman in for recalibration this week, and you don't take your old Snap-On, I'd end up with the more accurate wrench for the coming year.

 

Any ideas where you can get calibration checked/adjusted? Dare I ask: how much would that typically cost?

One thing I've done half-assedly: is set all of my torque wrenches to a common value, say around 35~40 foot/pounds, put them on a (torqued) lug nut, put a scrap of masking tape on the handle 12" out from the fulcrum. then hook on a digital suspension-style scale, pull till it displays that many pounds, listen for the click. They were all surprisingly in-the-ball-park.

 

Sounds like a good home made technique, assuming the digital scale is correct. We have a couple luggage scales and they match the airport readings most of the time. I sometime suspect that the scales at the ticket counter are pretty lax in their calibrations.

 

Me too, probably. Most of my torque wrenches are old Craftman USA ones, but I'd seriously consider these HF ones, which are well reviewed. One also should get a feel for what torque is right for different applications, and use that as a sanity check before you break something. Sorry, but sometimes you need to think.

From reading online car forums, a couple of common rookie mistakes that lead to broken fasteners are:

• Torquing a left handed thread fastener until it snaps, not realizing that your torque wrench does not click when going CCW. Not all do. Some of mine do, some don't. When torquing CCW, I always test on something that won't break to be sure the click is there.
• Believing a wrong number read online - one that should have been obviously too high if the person had been thinking - and snapping something.
• Making a similar mistake due to misunderstanding about what certain parts are called, so the wrong torque is applied and something breaks. For example, if you're about to torque an M6 fastener to 50 Nm, something is wrong, so stop.
• Whenever you hear about something coming loose, or the very rare cases of a wheel falling off, it is almost certainly due to someone simply forgetting to apply the final torque.

None of the above have anything to do with Snap On vs Harbor Freight.

 

All good points. But this one gets skipped way too often in the quest for accuracy:

 

Maybe... but, how LONG will it stay in calibration?
There are certain things that are just not worth getting cheap.

 

About the only thing I'd change would be this: instead of attaching the pull at exactly one foot just to make the arithmetic easy (ok, I pull 40 pounds at one foot, it's 40 foot pounds), just attach the pull at the center of the handgrip at the end of the wrench, measure the distance from there to the drive center and do the arithmetic. (So if that distance is, say, 19 inches, you pull with 40 * 12 / 19 = 25¼ pounds and that's 40 foot pounds.)

Sometimes the wrench is built on the assumption that the whole length of the handle is deflecting under the same applied force. That's definitely the case for the simple beam-type wrenches. If you're pulling from the middle of the handle, that's not what's happening.

 

That’s a good point!

 

I'm thinking maybe score a beam-style torque wrench? Just to try; they seem relatively bullet-proof.

And maybe: mounting it upside down in a vice and connecting a micrometer style torque wrench to it, you could test the latter?

 

They are pretty bulletproof. Plus, they develop your contortionist skills.

If the bolt is under the car facing east, you're under the car facing east so you can read the scale. If it's upside down facing west. you're upside down facing west ....

 

Generally they are not. The sensing mechanism measures torque at the head, so it does not matter whether you pull at the tip of the handle, or the middle of the wrench. But ...

Exactly right on the beam-type ones. Those are simpler, and you must pull on the handle. The Craftsman beam one I have actually has the handle mounted to the bar as a freely moving pivot. This cleverly means that you are unable to apply a torque at the handle, and the force you apply is applied exactly at the pivot point. This is all needed since, as you point out, for the beam-type wrenches, it depends where you grab it (and also if you were able to apply a torque with your hand as well as a force).

Also, if you use a torque extension on your non-beam-type torque wrench, you need to do a little math to calculate the torque at the end as a function of the torque wrench setting. And in that case, you also need to apply a pure force (no torque) and it needs to be at the middle of the handle (and the length from that point to the torque wrench head is a value used in the correction formula).

 

Doing a little torque wrench calibration checking. My 1/2" and 3/8" ones seem pretty much spot-on, using 30 lbs of dumbbells carefully placed at measured point along the handle. The bag weighs maybe 1/2 pound, not that much:



Then my 1/4" really seemed to be off, tripping too early. I figured out the adjustment, a fine-threaded collar just inside at the end of the handle, that you tighten or loosen. I had a bout of dyslexia, between the inch pound conversion and that the handle was shorter than a foot (meaning the suspended weight is less effective than if it was at a foot), but think I finally got it dialed in.


If someone wants to check my math on this last one:

That's a 5 lb weight, suspended 9" from the fulcrum, and it's just clicking when I set the torque wrench to 45 inch/pounds.

Does that sound right?

 

If I send you my torque wrenches, will you calibrate them?

Well done.

 

I think I left that 1/4" one tensioned. Seem to recall I found it thus last time.

Yeah not that hard to do.

 

Yeah always remember to have the minimum tension on them for storage.

Now you know why.