wing nuts clamping force

[Djinh]

Hi,

Does anyone have any data about what sort of clamping force can realistically be expected from a hand-torqued wing nut?

There is obviously no precise number possible, due to the huge differences in strength, etc. But I'm wondering if there are any ball-park figures available.

Alex

 

[KENAT]

I once had to do some testing to determine an answer for a similar question, though in my case it was a thumb screw like this one:

A test Engineer and I tightened on into a corresponding threaded hole and then measured the torque to remove it with a torque wrench (probably didn't adjust well enough for differences between fastening torque and un fastening torque). Each of us did this several times.

In my case I didn't so much need to know the clamp force as I needed to be able to replicate the act of torquing it several times as part of testing of a related component.

You can approximately back calculate clamp load from torque but it is very approximate unless you have good friction figures etc.

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[Djinh]

I thought about that, but figured it would be hard to account for friction.

If I'm going to measure, I'll probably take some (known rate) spring and see how far I can compress that by hand with the wing nut.

 

[KENAT]

You've also got to think you'll have big variability in what the fastening torque is.

Someone with small fingers/low pain tolerancer/poor grip.... may produce a much lower torque than someone with bigger fingers/higher pain tolerance/better grip...

I'm a reasonable size guy, but the test tech had something like 20% more torque than me on the screw I tested. If you'd opened up the sampling lot to more diminutive folk and 'the worlds strongest man' I'm sure you'd have got a bigger range.

Unfortunately the much vaunted ergonomics tables & references didn't seem to cover this load case when I was looking - but that was 15 or so years ago so things may have changed.

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[Tmoose]

What "clamping force can realistically be expected from a hand-torqued wing nut?"

The lowest realistic value is probably not going to be very high at all on wing nuts for 3/8" and smaller threads. As others said, weak or tired people with sore hands are sure to be among the tighteners.
Even before I became old. weak. and tired I often used a Crescent type adjustable wrench to loosen the tight ones or snug up the big ones.
Like this =

http://api.ning.com/files/gkyeY5S7f...enWingNutswithwrenchuntilheadsareflushNEW.jpg

The highest volume application that came to mind is air cleaner nuts on cars prior to 19?? and various lawn equipment. There is Plenty of flexibility in the air cleaner element and the housing as well, so tightening was more of a distance than a torque.

 

[MikeHalloran]

Here in magical SoFla, hurricane panels are typically retained at the bottom with nickel plated zinc wingnuts. They are a pain in the ass to apply or remove manually.

Luckily, you can also buy a special socket for dealing with them, comprising a hollow cylinder, notched at one end for the wings, equipped with a 1/4" hex nipple at the other end.

... which you insert into your battery powered impact driver.

... which is capable of breaking the captive studs attached to the house if you are overzealous.

So it's possible to get pretty near the breaking strength of a grade 2, 1/4-20 machine screw, with tools that are readily available.



Mike Halloran
Pembroke Pines, FL, USA

 

[CoryPad]

We can only give you torque because we do not know thread diameter, thread angle, thread pitch, friction coefficient, and inner and outer contact diameters between nut and mating part. From my own work, I have found that humans are limited to about 1.5 Nm when applying torque with fingers. You can do a search here on Eng-Tips, that number has appeared in previous threads too.

 

[Djinh]

1.5 Nm, that's a useful figure to start with, thanks

I know there'll be huge variability...

 

[BUGGAR]

I can't help but remembering those hanging drawing plan racks that used wing nuts to clamp the drawings. And tightening them with the handle of the 10 inch shears used to cut drafting paper from rolls.

 

[racookpe1978]

So you were the jerk that was always tightening them that hard! 8<)

I needed the scissors-handle-loop trick a few times to loosen them after "you" tightened them up! And I have got a pretty strong grip compared to most.

 

[tbuelna]

The max torque a person can apply to any particular form of wing nut would be limited by their finger strength and pain tolerance capability. This wing nut would hurt your fingers more than this one.

 

[oldrunner]

Don't know. I used to use a pair of pliers.

 

[1gibson]

Consider adding a spring lock washer, and instructions to tighten until it is just compressed. I won't argue in favor of it resisting vibration *but* the main value those have to me is you can visually see if something is "tight" or not.