On certain valve bodies, trans pans, etc., the 1/4" torque wrench is required. The 3/8" torque wrench simply doesn’t go low enough
If you’re doing a valve body under warranty and you don’t want that coming back on you because you overtorqued it . . .
Let’s not forget the TPMS sensors. Some of those nuts require very low torque, usually indicated in in-lbs . . . and often below the range of a 3/8" torque wrench
So let’s say this:
A pro will occasionally need the 1/4" torque wrench
The DIYer can probably get away without one
Some smartypants will probably say he doesn’t need a torque wrench, because he’s got a calibrated elbow, or because he knows that three veins equals 30 ft-lbs, or some such thing . . .
LOL
3 veins used to equal 30 ft-lbs. Now, at my age, it takes 6 veins (two arms).
Somewhere, pushed to the rear of a drawer, are 2 1/4" torque wrenches. A 'click" type and a beam type that are at least 30 years old and were used to adjust transmission bands long ago. But after adjusting quite a few I learned that even that procedure could be accomplished by feel using a nut driver. Even pre-loading rear ends does not require a torque wrench in most cases. Like installing tapered roller bearings on spindles, it’s all in the feel of the rotating hub. Or so it has seemed to me for quite some time. But if I were faced with overhauling a late model automatic transmission I might pull out the dusty torque wrenches and play it safe.
Torque wrenches are most accurate in the center of their range and are supposedly not too accurate at the extremes. I would certainly opt to ‘torque to feel’ rather than use a wrench at its upper or lower limit.
When it comes to very low torque values, those below 120 inch lbs, a click type torque wrench will simply not work, even if it can be adjusted below those values. Where I retired from, we had a couple of torque calibrators that we used to check the calibration of our torque wrenches. I used to bring mine in once in a while to see how they were doing.
The problem with a click type torque wrench is that when they click, the handle slips with you pressure in it which causes a bump in the applied torque. For example, when I would set a torque wrench to 75 ft lbs and put it on the calibrator, when applying pressure, you could see the torque readout on the calibrator climb and usually, the torque wrench would click as you reached the set value, but the calibrator recorded the peak applied torque and as soon as the torque wrench clicked, the applied torque would typically double. So 75 ft lbs would suddenly become 150 or so.
The peak torque would only be for a very short time, usually not enough to significantly move the nut or bolt but it was from the impact of the torque wrench slipping during the click. It does become significant at very low torques though because the nut or bolt can move quite a bit from the impact.
For very low torques, if the torque is very critical, only a dial type torque wrench is suitable. But for typical automotive applications, a beam type torque wrench used in bicycles shops is perfectly adequate. You used to be able to find these for under $10 many years ago when they were used a lot in transmission shops, but now they tend to cost a bit more.