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SMT electronics assembly manufacturing forum.


Hardware Torque requirements

jackofalltrades

#6570

Hardware Torque requirements | 14 May, 2001

Howdy, This subject may be a little off subject, but I have been looking for a source that can give me info for the recommended torque on hardware. What I would love to see, is a chart that can show me, for example a column for the screw size (SAE & Metric), a column for material it is made from, and then what torque should be used. So I could take, oh say an 8-32 aluminum screw and it will tell me to torque to 6 inch pounds, or whatever. ANSI has a confusing chart that is next to useless if you are not well versed in hardware threoy. Any idea folks? Thanks in advance.

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#6575

Hardware Torque requirements | 14 May, 2001

It's more complicated than that. Look here http://www.tohnichi.co.jp/en/measure/

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jackofalltrades

#6605

Hardware Torque requirements | 15 May, 2001

Dave, I took a look at the site you suggested and that is about what I've been running into. This also the reason I'm attempting to put something together. We have several dozen customers (contract manufacturing) and everyone wants the hardware torqued, naturally. Each customer seems to have their own idea about torque requirements and I'm trying to develop an "Instruction" (cross referenced to our own part #'s) that any operator could use and still be tracable back to something "official". Looks like a long road in a dark tunnel, I was just hopeing someone had a light.

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#6609

Hardware Torque requirements | 15 May, 2001

Screws are scary. I'll bet they don't need to be. On the other hand, lookit ... http://www.fastenersforelectronics.com/electronics/drivetorque.html

So, you're gunna get all those customers to buy-off on your torquing scheme? Ummm.

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CAL

#6613

Hardware Torque requirements | 16 May, 2001

STUMPED?? Is it the screw that determines the Torque setting or the assembly being fastened? All my Torque experience has been determined by the assembly..... Obviously the threads have torque specs but I dont think that is what we are talking about here.

Caldon W. Driscoll ACI USA 610-362-1200 cdriscoll@aciusa.org

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Boca

#6617

Hardware Torque requirements | 16 May, 2001

Some thoughts- Torque applied to each joint is case specific. I know there are charts and all, but they don't account for YOUR situation such as screwing a fab to a chassis(or your aluminum screw).

If the customer sets a spec then use it. (But it probably won't satisfy his requirements) So have an alternative value as a backup.

I like Dave's second reference. Do your homework, find the point of joint failure, and set a value of 50 or 60% of that.

It means you must have a torque control program. That is, how do you set your tools, how do you check your tools ...

I worked at a contract shop, #1 defect with one customer was 'loose fasteners'. They did not have specs, so I developed my own (some brass screws) and gave them a shot at disproving them. Put a torque control program in place. (you cann't believe the numbers on the side of many tools) After a little customer education (can't check tightness of a joint with the same value that made the joint due to 'joint relaxation') the problem went away. My point - IT CAN BE DONE!

Go for it.

Boca

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#6623

Hardware Torque requirements | 16 May, 2001

Cal please help me understand your point better. How does the assembly determine the torque requirements? Are you saying that you expect the assembly drawing to contain a torque specification? If not, how do you determine the torque from the assembly? Er, what?

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John

#6624

Hardware Torque requirements | 16 May, 2001

The size/type of screw and its preloaded torque are determined by the type and intensity of the load being applied to it. This should be known or estimated by the engineer that designed the product. Then they'll typicly apply a large safety factor to it. The amount of torque applied affects dramaticly how the screw behaves under fatigue loading. The designer of the product should supply the torque specification. If you want to come up with a procedure that goes back to something "official" it will take some work. If you're determined to pursue it, find a good machine design text book or desk reference.

John

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