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'Soft Loctite'?
David Jenkins - 5/11/20 at 02:14 PM

I want to make sure that a small screw on my carburettor doesn't come undone - but I do want to be able to undo it without damage if necessary. The screw is just a retainer, rather than load-bearing, but there will be a lot of heat and vibration. This means that I will need some form of thread-lock fluid, but I don't want it to be too strong.

Now I'm sure that Loctite has a perfect solution, but I don't know which one to get. I've needed to do a similar job in the past, so having a small pot on the shelf would be useful.

Can anyone offer advice?

McLannahan - 5/11/20 at 02:22 PM

I used to buy "low" strength Loctite threadlock for laptops - There's quite a few different strengths available but 222 looks like a good all rounder and the one I used.

https://www.henkel-adhesives.com/nz/en/insights/all-insights/blog/difference-between-threadlockers.html

jps - 5/11/20 at 03:31 PM

Would a little wrap of PTFE tape work? (Just thinking aloud).

Or, when i was about 9 I had a radio controlled car (built from a kit) which used a threadlock - it looks like Tamyia do a threadlock. It can't have been *that* strong if I was able to do/undo the nuts and bolts, but it must have had some locking effect...

Finally - i have a stick of this stuff:
Loctite 248 Threadlocker Medium Strength 19G Stick

Which i've used in a few places - but not tested in anger.

David Jenkins - 5/11/20 at 03:52 PM

quote:
Originally posted by McLannahan
I used to buy "low" strength Loctite threadlock for laptops - There's quite a few different strengths available but 222 looks like a good all rounder and the one I used.

https://www.henkel-adhesives.com/nz/en/insights/all-insights/blog/difference-between-threadlockers.html


I think you're right - 222 seems to be exactly what I need.

Thanks to all!

nick205 - 5/11/20 at 03:53 PM

David,

Loctite do a range of "strengths" of threadlock for different purposes. We use several different grades at work, IIRC the 222 we use on M4 set screws to secure steel enclosre parts together. Similar reasons you give, we need to avoid accidental loosening due to vibration, but need to be able to remove the screw without damaging the screw head, tool or thread. It's worked fine for that purpose for us for a number of years.

Personally I've only ever used PTFE in plumbing (water pipe) applications and found it works just fine. Not sure I'd trust it with much heat though.

jps - 5/11/20 at 04:17 PM

quote:
Originally posted by nick205
Personally I've only ever used PTFE in plumbing (water pipe) applications and found it works just fine. Not sure I'd trust it with much heat though.

On the basis it's wrapped around the threads on the water jacket outlets from my woodburner, i'd say it copes with reasonably warm temperatures quite well!

David Jenkins - 5/11/20 at 05:53 PM

If you overheat PTFE it gives off poisonous fumes...

MikeR - 6/11/20 at 08:02 AM

but in a open topped sports car with the small amount in use ........ would you notice a few extra poisious fumes?

(i appreciate that is not the correct approach - i'm in one of those moods this morning)

Russell - 6/11/20 at 08:53 AM

Cut a short length of rubber band and trap it in the screw thread. Old school thread lock.

David Jenkins - 6/11/20 at 09:08 AM

quote:
Originally posted by Russell
Cut a short length of rubber band and trap it in the screw thread. Old school thread lock.


Tricky - it's only an M3 thread, about 8mm long! Small, but a PITA if it falls out...

nick205 - 6/11/20 at 12:11 PM

Is there any chance of securing the screw head once it's in position?

i.e. wrap a bit of lock wire round the carb and over the screw head (laid in the groove if it's a flat blade screwdriver head)?

Just an idea for an alternative solution.

Failing that would a dot of super glue maybe secure it in place.

indykid - 6/11/20 at 12:38 PM

quote:
Originally posted by David Jenkins
quote:
Originally posted by McLannahan
I used to buy "low" strength Loctite threadlock for laptops - There's quite a few different strengths available but 222 looks like a good all rounder and the one I used.

https://www.henkel-adhesives.com/nz/en/insights/all-insights/blog/difference-between-threadlockers.html


I think you're right - 222 seems to be exactly what I need.

Thanks to all!


Also worth noting 222 is recommended for fasteners below M6. 243 (blue) is for fasteners M6 and over.

ISTR there's a viscosity difference between them too, probably so the 222 doesn't get wiped out of small threads

David Jenkins - 6/11/20 at 02:00 PM

quote:
Originally posted by nick205
Is there any chance of securing the screw head once it's in position?

i.e. wrap a bit of lock wire round the carb and over the screw head (laid in the groove if it's a flat blade screwdriver head)?

Just an idea for an alternative solution.

Failing that would a dot of super glue maybe secure it in place.


Wiring the screw would be overkill - it's very likely that the screw will never come out without external force (i.e. an allen key) as it's a retainer/locator for something else - it's not holding any load and it's firmly screwed in place. It's just that I'd rather be sure!

Of course, I might just be stressing too much about it...

UPDATE: Little pot of Loctite 222 now ordered.

[Edited on 6/11/20 by David Jenkins]

rusty nuts - 7/11/20 at 11:13 AM

A blob of paint on the threads would do the job, strong enough to hold but easy to unscrew using normal hand tools. It was a common thing to see on carbs at one time

coyoteboy - 19/11/20 at 11:23 AM

222 if you fancy buying a new thing.
Nail varnish, or epoxy on the head if you don't.

[Edited on 19/11/20 by coyoteboy]