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

[kakalee1]

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.

 

[dik]

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

Dik

 

[SnTMan]

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

 

[dik]

Thanks for the correct spelling

Dik

 

[drawoh]

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

 

[SnTMan]

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

 

[MintJulep]

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.