torque wrench calibration, torquing technique general
 

In the past, I've just trusted the click wrench, but after reading tons of articles about bolt stretch and preload and alloys and shit, I'm scared of not doing a near-perfect job and my precious motor spins a bearing or something.

I talked to my dear comrades at the machine shop and they said they used a click wrench for most tasks but they would periodically double check it against a beam wrench. This seemed like really solid advice, but I've seen some really cool digital things that look like they have potential ( ). I'm basically sold on the beam type but I'm leery of trying to accurately read a dial while pulling on something with 60 lbs of force.

I'm open to suggestions, especially from people that have assembled multiple engines without them falling apart later on.

I use a JET click wrench for just about anything...I keep it in it's case and at zero when not in use. I've checked against others and it's usually within a few ft/lbs which is great for any engine I've assembled.

Any engine that has come apart on me has had nothing to do with improper torque specs. You should be fine IMO

I bought a beam type at sears a while back after finding my click type set my head bolts at 40 ft*lbs instead of 65. I checked it by building a fixture I clamped to my bench and hanging weights on it. It was dead on accurate at the 2 weights I checked.

I had no problem at all using it to do head studs. Yeah a click type is faster, but it's no problem to use a beam type. If you were local I'd let you use mine to see, but they're only 25 bucks at Sears for the one I bought.

EDIT: And my engine hasn't fallen apart, running 30 PSI boost.

Beam wrenches generally have peak hold needles, right? All the ones I ever used have.

So then all you need is sockets, nuts and bolts. Hook the clicker to the beam, and see what the peak click value is. The beam wrench is always calibrated unless you heat treat it or something.

You don't even need and nuts and bolts -- there's a size of 12 point socket that will fit over 1/2" square drive (I forget which one it is) and that lets you hook the two wrenches directly to each other.

https://www.miataturbo.net/attachmen...ine=1453838488

Set the click-type to the torque spec you want, use the beam type to measure the point at which it actually breaks. Adjust until you get what you want, do it a few more times to check that it's repeatable, and then use that settings on the click-type. Trying to actually use a beam-type while tightening is a PITA.

For rods you should be using a bolt stretch gauge, not a torque wrench.

https://www.miataturbo.net/attachmen...ine=1453838488

--Ian

Not knocking its legitimacy, but how many of you get away with using just a torque wrench for rods without using a bolt stretch gauge?

I've never measured bolt stretch, never lost a rod, rev'd to the moon and ran all the boost. Measuring stretch is a better method though, and if I had the tools to do it, I would.

Both methods are trying to measure preload in the bolt, but the problem with torque is that something like 80% of the torque value comes from the friction, not the actual preload, and that friction varies with a lot of stuff. So to get accurate results with a torque wrench you need to be following the manufacturer's specified procedure exactly -- everything spotlessly clean, properly burnished, no thread damage, specified lubricant (no substitutions) applied in all the right places and no others, torque wrench calibrated, etc.

With a bolt stretch gauge the friction isn't relevant any more, thus you can get a repeatable result with a lot less worry about the exact procedure. They're $50 at Summit -- cheap insurance in my book.

--Ian

stupid question, using the bolt stretch gauge, how do you know how far to stretch the bolts when tightening?

Its written in the bolt/ stud instructions and or spec sheet. I also use this on rod bolts. the Lunati brand, from summit was like 50 bucks.

ARP lube threads and under washer or bolt head surface, clean, and a good torque wrench. Never lost an engine in 50+ years from a torque issue. There is alot of debate on which way is best.

Ive used my sears beam on at least 5 engine(automotive) builds, all are still running.

1.) Torque is just a force times a length (lbs times ft = lbft). I used to work in calibration (US Army Primary Standards Lab calibration technician my last couple years of collage), and the easiest way to get a traceable torque to perform a calibration with is to clamp the torque wrench to a workbench, and apply a calibrated mass at a calibrated length using a precisely measured jig. If it clicked at the indicated wrench setting corresponding to the torque you just applied, and didn't click at the setting one lbft above it, you were calibrated.

2.) Having said that, I calibrated my personal Husky torque wrench by clamping the square drive in a vice, and applying 25 lb weights to a piece of chain hung a foot from the center of the drive square, as measured with a ruler. This was a shitty calibration, but it measured out plus or minus a single ftlb repeatably, and I'm cool with that.

3.) We calibrated ~50-100 torque wrenches a year (this is usually a secondary or transfer lab task; it shouldn't have been our responsibility). We found that torque wrenches tended to remain within a tiny percentage of the calibration numbers from year to year unless they were obviously abused. I don't believe that it really matters in real use if you store your torque wrench at zero or not.

4.) A bolt stretch gauge is the correct tool for measuring rod bolts. At $50, it seems ludicrous not to buy the correct tool for a job like this.

Nothing will make a torque wrench lose calibration faster than loosening bolts with it.
It's amazing how many PhD's I work with that don't know the difference between a torque wrench and a regular ratchet.

http://www.amazon.com/s/ref=nb_sb_no...+torque+wrench



Buy any torque wrench from this brand, you'll be fine. Store at zero, even though split beam wrenches don't require it.

Personally, I prefer click-type or spit beams. Dial type, in my opinion, are much harder to use at high torque levels or limited access situations.




It's all about technique, and sequence. You need to make a smooth gradual pull until the required torque is met.