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How to prevent screw from loosening due to thermal expansion and thermal cycle

How to prevent screw from loosening due to thermal expansion and thermal cycle

How to prevent screw from loosening due to thermal expansion and thermal cycle

(OP)
Hi,

I have an application where two aluminum plates (6061) are joint together by screws. One plate has a counterbore hole while the other plate has a threaded hole. I haven't decided on the screw size yet, but it will be between 1/4-20 and 1/2-13.
The plates will be subjected to 250C with possibility of thermal cycle between 200-250 C.

How do I prevent the screw from loosening? would a lock washer help?

Fasteners are not my strong suit, and I would love to learn more about it. If anyone can point me to a good reference i.e. book, paper, website, I would greatly appreciate it.

Best,
NL.

RE: How to prevent screw from loosening due to thermal expansion and thermal cycle

Can you use a bolt? and with Belville washers? We've found the washers to be quite good with thermal cycling...

Dik

RE: How to prevent screw from loosening due to thermal expansion and thermal cycle

kakalee1, a normal lock-washer will not help, a Belleville washer might.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: How to prevent screw from loosening due to thermal expansion and thermal cycle

Thanks for the correct spelling

Dik

RE: How to prevent screw from loosening due to thermal expansion and thermal cycle

kakalee1,

250°C is a lot for 6061-T6 aluminium. I suggest you Google "creep".

The stack of Belleville springs sounds like a good way to retain clamping force after the aluminium creeps.

--
JHG

RE: How to prevent screw from loosening due to thermal expansion and thermal cycle

One does not often get the opportunity to correct dik :)

[Actually, I didn't see your post before making mine]

The problem with sloppy work is that the supply FAR EXCEEDS the demand

RE: How to prevent screw from loosening due to thermal expansion and thermal cycle

How thick are the plates?
How long are the screws?
What is the temperature at assembly time?

See the FAQs here for plenty of good reference book suggestions.

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