Lock-tight recommendations? 3

[GraemeMath]

I’ve got to attach a copper plate onto a piece of steel with 4 screws. The plate is there solely to stop any damage being done to the steel.

The component is part of a deep sea tool, and the copper plate will be in contact with Panelin control fluid, and temperature (Probably max 250 degrees C).

The screws holding on the plate are M8 screws, but these cannot vibrate or work themselves loose at all.

So, I’m looking for a lock tight solution that can be inserted into the holes before the screws are inserted. The screws must be able to be removed if needed, so this lock tight solution cannot be fully permanent.

Have you got any suggestions as to which solution might work best?

Thanks,

Graeme Mathieson.

 

[Heckler]

I would consider other mechanical locking methods....for example using locking heli-coils in the parent material.

Loctite has a very comprehensive product matrix that can guide you in yoru search

http://www.loctite.com/

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
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(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right." -- George Best

 

[GraemeMath]

Thanks Heckler. It's not me who is designing it, I've just been asked to look up some information on loctite.

The designer said that locking heli-coils were not feasible.

Thanks for the link.

Graeme

 

[desertfox]

Hi GraemeMath

Will there be an issue with corrosion (steel & copper)?


regards

desertfox

 

[byrdj]

I believe temperature will be your problem. Lok-tite's stregnth is greatly reduced at 150C (25%)

low strenght "purple" is

http://tds.loctite.com/tds5/docs/222-EN.PDF

common medium strenght "blue" is

http://tds.loctite.com/tds5/docs/242-EN.PDF

med-high strenght "red" is

http://tds.loctite.com/tds5/docs/262-EN.PDF

high strenght "red" is

http://tds.loctite.com/tds5/docs/272-EN.PDF

 

[Heckler]

If you can not use a locking heli-coil then use a fastener with a self-locking thread form.

I just don't think Loctite is your best solution with the information you have given us.

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
XP Pro SP2.0 P4 3.6 GHz, 1GB RAM
NVIDIA Quadro FX 1400
o
_`\(,_
(_)/ (_)

(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right." -- George Best

 

[Heckler]

Here is another option we've have used before:

http://www.spiralock.com/

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 3.0 & Pro/E 2001
XP Pro SP2.0 P4 3.6 GHz, 1GB RAM
NVIDIA Quadro FX 1400
o
_`\(,_
(_)/ (_)

(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he's all right." -- George Best

 

[GraemeMath]

Thanks a lot for the input and the links so far everyone.

I'm not sure about the corrosion, it is something I will flag up with the engineer who asked me to look into this.


Heckler - Those spirallock's look very useful. I'll see if that can be used instead.

Thanks,

Graeme

 

[GraemeMath]

"If you can not use a locking heli-coil then use a fastener with a self-locking thread form."


Can those be removed easily enough?

 

[Cheddarcaveman]

Just a simple Lock-washer should do the trick, either the split or full circle type. Can be undone and replaced each time you undo the bolts.

 

[GraemeMath]

Nice one. Cheers.

 

[GraemeMath]

Ok guys, got this sorted. I was wrong with the temperature range. It shouldn't be any higher than 150C, so the medium strength loctite should suffice.

Thanks for all the input.

Regards,

Graeme

 

[ScottyUK]

If a screw loosening could lead to danger or to damage to a high value asset, consider wire-locking as used in the aviation and turbine industries. If the screws are the Allen socket type then wire-locking becomes fairly simple to implement. Temperature won't be an issue at 250C.


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Sometimes I only open my mouth to swap feet...

 

[CoryPad]

Split helical washers and lock-wire do not prevent fastener pretension loss nor joint loosening. You can read SEVERAL threads at this site (with many published references) that discuss this. Thread adhesive can prevent these problems, and 150 [&deg]C is a standard heat-resistance level for these products.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Twoballcane]

I agree with CoryPad especialy for vib issues. Lock washers / split washers turn to spaghetti under shock and vib.

Tobalcane
"If you avoid failure, you also avoid success."

 

[MintJulep]

In fact, we have a FAQ about lock washers:

faq404-1257

 

[Tmoose]

Depending on the materials, shapes and sizes of the plates, the thermal expansion of the copper may be about 50% greater than the steel plate. May need to make allowances or provisions.

 

[GraemeMath]

Cheers folks. Good input.

The plate is brass, not copper. I put copper by mistake in my first post.


Thanks,

Graeme