Torque developed by thumb and finger 7

[tmech77]

How much torque can an average man develop when tightening a #6-32 nut, using just his thumb and first finger? The nut is 5/16" hex and 1/2" tall. It is a coupling nut. I am using a tall coupling nut instead of regular height nut, so I can get more torque on it. I may also use a hex thumb screw. The hex on that is about the same as on the coupling nut. The coupling nut is a little taller, so it lets you get a better grip. I dont think it will really matter, but the material is zinc plated steel and there is no lubricant being used. Please site references if you have some. Thanks for the help.

 

[Nereth1]

Surely there are about 10-15 simple ways to test this with parts you have lying around?

Take one of the screws in question, screw it into a handy piece of wood, put the shank on a knife edge (read: the side of a ruler or just about any other object in an office), and then twist the screw as hard as is reasonable against either a spring balance hooked into a hole drilled into your piece of wood, or a set of weighing scales, or a known mass, etc etc.

Ask half a dozen people in your office to do it and take the weakest or strongest or whatever is relevant to your issue.

If greasy hands/wet hands/towels to increase friction or something like that is a factor, remember to include it in your test.

 

[racookpe1978]

Nope. Can't tell you.

Am I the typical ignoramus from whom we (you and I) need to be protect the nut and threads against mis-handling? (And cross-threading.)

Do I "really" want to put some energy into that nut and so will tighten my hand and wrist, am I a car nut or trained user who knows how firmly that nut must tightened to work right, or am I an instrument tech who cares for his tools and his delicate wiring?

Buy a light-weight (inch-pound or less) torque wrench and measure the back-force by at least 12 people 4 times each.

 

[CoryPad]

Personal research on this subject has identified 1.5 N[·]m as a reasonable value.

 

[KENAT]

Once spent a bunch of time researching similar (M8 thumb screw) looking up the DefStan anthropometric tables etc. and couldn't get a good answer.

I resorted to me and a lab tech measuring the torque we could generate (his was a got bit higher than mine) applying a significant safety factor and going from there.

Is your concern being able to attain a minimum torque required or a maximum torque exerted?

Also remember torque required to remove a nut (especially if it's been on there a while) will tend to be more than that you installed it with.

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[drawoh]

How much torque can an average man develop...

Average man or average person?

--
JHG

 

[IRstuff]

The torque specs on thumbscrews might give you an idea

http://www.kipp.com/xs_db/DOKUMENT_DB/

http://www/KIPP_DE_CH_PL/BEDIENTEILE/DataSheet/en/K02/K0277_Datasheet_1075--en.pdf

http://www.carrlane.com/catalog/ind...006280B1713050245221E0107070F1A3C3B2853524154

TTFN
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[1gibson]

How do you know the user is only going to use their bare hands? You need instructions to tell them not to use tools, so elaborate a little bit more there. And/or use a threaded round standoff if you are concerned the max torque will damage something.

 

[rb1957]

ah, the definition of "finger tight" !

i guess "not much" isn't precise enough ?

Quando Omni Flunkus Moritati

 

[ctopher]

No way to know. One can torque more than the next.

Chris, CSWA
SolidWorks 14
ctopher's home
SolidWorks Legion

 

[3DDave]

rb1957 - in a delicate item it may be too much!

In JR high shop class I could not tighten the thumbscrew on the jigsaw enough to hold the blade. I got a small crescent wrench. What the unfortunate shop teacher got was the chance to figure out how to remove the fragment that was left. Good times.

 

[MintJulep]

From MIL-STD-1472: Recommended maximum torque for an adjustment knob operated by a fingertip grip is 4.5 inch ounces.

That's an order of magnitude less than CoryPad's 1.5 Newton meter figure.

 

[rb1957]

3DDave ... sure there are times when you have to be very careful ... this should be recognised by the designer and the user.

Quando Omni Flunkus Moritati

 

[KENAT]

Any answer with a single value and little or no context is almost meaningless. That's why I asked more specifically about what torque you care about.

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[redpicker]

From MIL-STD-1472: Recommended maximum torque for an adjustment knob operated by a fingertip grip is 4.5 inch ounces.

Shouldn't that be 4.5 ounce-inches?

See thread

http://eng-tips.com/viewthread.cfm?qid=362357

rp--[Running away while ducking various torque wrenches being thrown at me]

 

[msquared48]

The answer is way to variable to establish a standard value as some people get a lot more torqued than others.

Mike McCann
MMC Engineering

 

[GregLocock]

On a 40mm nut the typical value for fingertight was 1.4 Nm, your nut is smaller, but you are looking for a maximum. Worst case scenario is of the order of nut radius*200N, which works out about the same.

Hoever if the operator has a pair of pliers in their pocket, all bets are off.

Cheers

Greg Locock


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[tbuelna]

The MIL-STD anthropometric data noted by MintJulep are recommended design limits for the 90th percentile human. These values do not necessarily mean that an "average man" could not easily do better. I'm pretty sure the average adult male from west Texas has a much greater index finger/thumb grip strength than the average adult male from West Hollywood.

 

[tmech77]

I was planning on using a #6 pem stud in 1/8" alum sheet. A thumb screw nut would go on the stud. The PEM catalog says the max torque the pem stud can take is 9 in-lbs. I was hoping that a person's fingers would not be able to tighten a small #6 nut tighter than 9 in-lbs, but what I am seeing is that some of you have stated that it might be around 1.4 or 1.5 Nm, which is about 12 or 13 in-lbs. But then someone else said it would be around 4.5 ounce-inches, which is only about .28 inch-pounds. It looks like it could vary quite a lot. I did use a torque screwdriver to tighten a screw and nut to 6 in-lbs and was not able to unscrew them with my fingers. Thanks to all of you for your advice.