Draper Beam-indicating Half-inch drive. - Torque Wrench Technique Question

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Sun 16 Mar 2014 04:53
Draper Beam-indicating Half-inch drive. - Torque Wrench Technique Question - edlithgow

Just used one on the gf's scooter head bolts, and realised I wasn't exactly sure how! Embarassing


(I've used one before but a long time ago, and maybe I didn't think of this before)


My uncertainty is with the interpretation of the standard "tighten nut until the specified torque is reached" instruction.


Just now, when I did that, the nut was still moving.


Should I stop at that point (as the standard instruction seems to imply), or hold the torque at that level until rotation stops?


The former seems likely to vary, depending on how fast you tighten the nut.


The latter seems likely to be more reproducible, but also likely to get the nut a lot tighter.


This is using a beam-deflection wrench.


I suppose, with the click-type, (which I don't have) you don't have the option of holding at the set torque value, but the rate at which you reach it must still influence the final tightness of the nut?

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Mon 17 Mar 2014 22:52
Draper Beam-indicating Half-inch drive. - Torque Wrench Technique Question - Bolt

Not sure if this is a wind up question,but the answer is stop when you reach the required torque,if you carry on you run the risk of shearing it off,depending how tight it has to be and whether its lubricated or dry thread(makes a difference)

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Tue 18 Mar 2014 07:54
Draper Beam-indicating Half-inch drive. - Torque Wrench Technique Question - craig-pd130

A click-type torque wrench is much easier to use, and a reasonable one costs about £20.

Autoexpress recently tested the accuracy of a range of torque wrenches, from the £15 cheapies to £250+ SnapOn tools. The test found that there was no correlation between price, and accuracy of calibration as supplied -- none of the wrenches was more than 7% inaccurate, and the most accurate was one costing about £30 (Halfords branded, if I recall correctly).

Edited by craig-pd130 on 18/03/2014 at 07:55

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Tue 18 Mar 2014 08:55
Draper Beam-indicating Half-inch drive. - Torque Wrench Technique Question - edlithgow

Thanks for both replies.

No wind up intended, was a genuine concern, but from a bit of reading, its apparently generally acknowledged that torqueing bolts is a very imprecise procedure, which the second reply here confirms, so I feel a bit better about it now.

I suppose if you increase the torque gradually, so movement has time to happen, and you approach the "click-point" slowly, that should reduce any variability due to technique.

Re stopping when you reach the required torque, the distinction between that and holding at the required torque, while its a real one, depends on the reading precision of the device with a beam-indicating wrench. Since, within those limits, the specified torque isn't exceeded, I'm going to stop worrying about it., at least until I break something.

I like the beam type because there's little to go wrong with the mechanism. Given the very infrequent use, and lack of calibration, thats a consideration.

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Wed 19 Mar 2014 10:00
Draper Beam-indicating Half-inch drive. - Torque Wrench Technique Question - edlithgow

Not sure if this is a wind up question,but the answer is stop when you reach the required torque,if you carry on you run the risk of shearing it off,depending how tight it has to be and whether its lubricated or dry thread(makes a difference)

Yes, friction/lubrication is probably a large variable, and I'm generally working with oiled or greased bolts, (while dry is usually specified/assumed) which'll tend to cause over-tensioning.

I don't like stripped threads, but I don't like seized/stuck threads either.

This thread

www.thumpertalk.com/topic/426292-greasing-all-bolt.../

includes a suggestion to torque down dry to 1/3 of spec, and then record the angular movement required to reach final spec.

You then repeat that movement with a lubed fastner, so it reaches the same position (and hence tension) though the torque, if you measured it, would be less due to the lube.

The assumption is that at the 1/3 starting/reference point the torque isn't significantly affected by the lube.

I dunno about that, but I'd think if you counted total turns from the start, that assumption wouldn't need to be valid anyway.

Think I'll try that in future, if there is a future.

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Wed 19 Mar 2014 10:43
Draper Beam-indicating Half-inch drive. - Torque Wrench Technique Question - craig-pd130

There's a school of thought that suggests always lightly lubing threads and under the nut, to remove variability introduced by friction resulting from slight corrosion on older threads, etc, to get true consistency in torque settings when you're NOT using brand-new bolts, nuts, washers etc

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Thu 20 Mar 2014 01:39
Draper Beam-indicating Half-inch drive. - Torque Wrench Technique Question - edlithgow

For an apparently simple question, it gets quite complex when you get into it.

In this case these's another potential variable I hadn't thought of.

Since these were domed head nuts, and I'd greased the studs (albeit lightly) there would seem to be a possibility of hydraulic/pneumatic lock within the nut, which could distort the relationship between tension, thread load, and torque.

My head hurts.

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