Discussion:
Removing Loctite fixed screws
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rick
2016-12-06 15:21:20 UTC
Permalink
I need to undo 4 x CSK stainless steel screws 3/8x24 UNF
These are screwed into 7000 series anodized billet aluminium.

Fixed by a Loctite (or similar) thread lock

The heads are imperial allen socket.

From past experience I know that even non-Loctite ones can be difficult
to remove, the screws being stainless are relatively soft and they will
round out easily.

Any thoughts over best approach .... I could leave a soak in Plus-gas
penetrating oil, but unsure if that will help .... or I could apply heat.

If the latter then how much to help break Loctite, without damaging
anodized finish or softening screw. .... I have a micro propane torch so
could apply localised heat ...

I also have a pneumatic impact wrench .. I could also use that rather
than just allen socket in ratchet handle
RustyHinge
2016-12-06 15:50:52 UTC
Permalink
Post by rick
I need to undo 4 x CSK stainless steel screws 3/8x24 UNF
These are screwed into 7000 series anodized billet aluminium.
Fixed by a Loctite (or similar) thread lock
The heads are imperial allen socket.
From past experience I know that even non-Loctite ones can be difficult
to remove, the screws being stainless are relatively soft and they will
round out easily.
Any thoughts over best approach .... I could leave a soak in Plus-gas
penetrating oil, but unsure if that will help .... or I could apply heat.
If the latter then how much to help break Loctite, without damaging
anodized finish or softening screw. .... I have a micro propane torch so
could apply localised heat ...
I also have a pneumatic impact wrench .. I could also use that rather
than just allen socket in ratchet handle
I don't know how much heat to apply - rather, I don't know the
temperature that is required, but heat it has to be, unless they've
found something new.

IIRC Loctite is acrylic.

I think the drill (NO! Not the drill!) is to heat it and then use the
impact wrench *lightly* if that can be done with the pneumatic version.
Make sure the hexagon bits are correct for the job: even a
loosely-fitting hexagon drive can make a mess of the contact areas.
--
Rusty Hinge
To err is human. To really foul things up requires a computer and the BOFH.
rick
2016-12-06 16:58:49 UTC
Permalink
Post by RustyHinge
IIRC Loctite is acrylic.
I think the drill (NO! Not the drill!) is to heat it and then use the
impact wrench *lightly* if that can be done with the pneumatic version.
Make sure the hexagon bits are correct for the job: even a
loosely-fitting hexagon drive can make a mess of the contact areas.
Maybe I need to buy a new hex bit ..
e***@whidbey.com
2016-12-06 17:26:28 UTC
Permalink
On Tue, 6 Dec 2016 15:21:20 +0000, rick
Post by rick
I need to undo 4 x CSK stainless steel screws 3/8x24 UNF
These are screwed into 7000 series anodized billet aluminium.
Fixed by a Loctite (or similar) thread lock
The heads are imperial allen socket.
From past experience I know that even non-Loctite ones can be difficult
to remove, the screws being stainless are relatively soft and they will
round out easily.
Any thoughts over best approach .... I could leave a soak in Plus-gas
penetrating oil, but unsure if that will help .... or I could apply heat.
If the latter then how much to help break Loctite, without damaging
anodized finish or softening screw. .... I have a micro propane torch so
could apply localised heat ...
I also have a pneumatic impact wrench .. I could also use that rather
than just allen socket in ratchet handle
Once cured loctite anaerobic adhesives won't dissolve in any of the
usual solvents. The permanent stuff must be heated to 450F to break
down enough for the fastener to be removed. That's probably too hot
for your 7075, you don't want it to lose any of its temper. What I
would do is try penetrating oil and heating the aluminum as hot as
possible without risking the los of temper. The aluminum will expand
away from the steel fastener and this may allow the penetrating oil to
wick in and break the bond.
Eric
rick
2016-12-06 19:50:42 UTC
Permalink
Post by e***@whidbey.com
Once cured loctite anaerobic adhesives won't dissolve in any of the
usual solvents. The permanent stuff must be heated to 450F to break
down enough for the fastener to be removed. That's probably too hot
for your 7075, you don't want it to lose any of its temper. What I
would do is try penetrating oil and heating the aluminum as hot as
possible without risking the los of temper. The aluminum will expand
away from the steel fastener and this may allow the penetrating oil to
wick in and break the bond.
Eric
What temp is it safe to go to without affecting temper (or anodized finish)

I had thought about just heating the face of the screw to such a temp.
David Billington
2016-12-06 21:23:12 UTC
Permalink
Post by rick
Post by e***@whidbey.com
Once cured loctite anaerobic adhesives won't dissolve in any of the
usual solvents. The permanent stuff must be heated to 450F to break
down enough for the fastener to be removed. That's probably too hot
for your 7075, you don't want it to lose any of its temper. What I
would do is try penetrating oil and heating the aluminum as hot as
possible without risking the los of temper. The aluminum will expand
away from the steel fastener and this may allow the penetrating oil to
wick in and break the bond.
Eric
What temp is it safe to go to without affecting temper (or anodized finish)
I had thought about just heating the face of the screw to such a temp.
I'm not an expert on heat treating aluminium but I was recently asked
about filling some dings in an aluminium bicycle frame made of 7005 and
the maker mentioned that was artificially aged to strengthen the frame
after welding at 315C (600F). It's not like steel where heating above
certain limits will temper the alloy, rather it has to be heated much
higher to put various elements into solution then quenched to keep them
there leaving it in a soft state, the artificial aging allows those
elements to precipitate out and harden the alloy. The thought on the
bicycle frame was to use a low temperature solder to fill the dings
before powder coating as none of the powder coaters were confident the
powder coat fillers would work in the application.

Regarding heating the fastener to soften the loctite, earlier I looked
up the technical data on 603 regarding fits but noted it mentions
heating to 250C for dismantling and doing so while hot.
RustyHinge
2016-12-12 13:12:28 UTC
Permalink
Post by rick
Post by e***@whidbey.com
Once cured loctite anaerobic adhesives won't dissolve in any of the
usual solvents. The permanent stuff must be heated to 450F to break
down enough for the fastener to be removed. That's probably too hot
for your 7075, you don't want it to lose any of its temper. What I
would do is try penetrating oil and heating the aluminum as hot as
possible without risking the los of temper. The aluminum will expand
away from the steel fastener and this may allow the penetrating oil to
wick in and break the bond.
Eric
What temp is it safe to go to without affecting temper (or anodized finish)
I had thought about just heating the face of the screw to such a temp.
Unfortunately you will be expanding the screw into the aluminium, making
it a tighter fit - however, it might have broken the Loctite
sufficiently to let it move once it cools.

Now if you had a tiny liquid nitrogen dispenser...
--
Rusty Hinge
To err is human. To really foul things up requires a computer and the BOFH.
pyotr filipivich
2016-12-07 03:23:30 UTC
Permalink
Post by e***@whidbey.com
possible without risking the los of temper. The aluminum will expand
away from the steel fastener
The trick is to have the heat expand the aluminum 'faster' than it
does the steel screw.
Or, to figure a way to chill the steel screw enough to break the
loctite.
Thermal expansion is a tricky ting to work with.
--
pyotr filipivich
Next month's Panel: Graft - Boon or blessing?
rick
2016-12-07 12:38:01 UTC
Permalink
Post by pyotr filipivich
Post by e***@whidbey.com
possible without risking the los of temper. The aluminum will expand
away from the steel fastener
The trick is to have the heat expand the aluminum 'faster' than it
does the steel screw.
Or, to figure a way to chill the steel screw enough to break the
loctite.
Thermal expansion is a tricky ting to work with.
I suppose I could put heat on aluminium with heat gun ... directly over
where it is threaded - and then spray freeze spray onto screw face
pyotr filipivich
2016-12-07 15:26:09 UTC
Permalink
Post by rick
Post by pyotr filipivich
Post by e***@whidbey.com
possible without risking the los of temper. The aluminum will expand
away from the steel fastener
The trick is to have the heat expand the aluminum 'faster' than it
does the steel screw.
Or, to figure a way to chill the steel screw enough to break the
loctite.
Thermal expansion is a tricky ting to work with.
I suppose I could put heat on aluminium with heat gun ... directly over
where it is threaded - and then spray freeze spray onto screw face
Might work. "Try it and report back to the class." :)
--
pyotr filipivich
Next month's Panel: Graft - Boon or blessing?
Colin Docherty
2016-12-07 10:15:48 UTC
Permalink
Back in the day I had a similar dismantling problem, spoke to Douglas
Kane ( Loctite Agents ) and was told they use a hair drier as it
softens/weakens the loctite enough without risking damage to componants.
Loctite show graphs of temp versus strenth at different temps. Even
boiling water will lower strength by 30 to 60 % depending on grade.

Regards Colin
Post by rick
I need to undo 4 x CSK stainless steel screws 3/8x24 UNF
These are screwed into 7000 series anodized billet aluminium.
Fixed by a Loctite (or similar) thread lock
The heads are imperial allen socket.
From past experience I know that even non-Loctite ones can be difficult
to remove, the screws being stainless are relatively soft and they will
round out easily.
Any thoughts over best approach .... I could leave a soak in Plus-gas
penetrating oil, but unsure if that will help .... or I could apply heat.
If the latter then how much to help break Loctite, without damaging
anodized finish or softening screw. .... I have a micro propane torch so
could apply localised heat ...
I also have a pneumatic impact wrench .. I could also use that rather
than just allen socket in ratchet handle
rick
2016-12-07 12:39:14 UTC
Permalink
Post by Colin Docherty
Back in the day I had a similar dismantling problem, spoke to Douglas
Kane ( Loctite Agents ) and was told they use a hair drier as it
softens/weakens the loctite enough without risking damage to componants.
Loctite show graphs of temp versus strenth at different temps. Even
boiling water will lower strength by 30 to 60 % depending on grade.
Regards Colin
OK I have an electric heat gun .... so this might be better approach
John H
2016-12-07 22:03:01 UTC
Permalink
Post by rick
I need to undo 4 x CSK stainless steel screws 3/8x24 UNF
These are screwed into 7000 series anodized billet aluminium.
Fixed by a Loctite (or similar) thread lock
The heads are imperial allen socket.
From past experience I know that even non-Loctite ones can be difficult
to remove, the screws being stainless are relatively soft and they will
round out easily.
Any thoughts over best approach .... I could leave a soak in Plus-gas
penetrating oil, but unsure if that will help .... or I could apply heat.
If the latter then how much to help break Loctite, without damaging
anodized finish or softening screw. .... I have a micro propane torch so
could apply localised heat ...
I also have a pneumatic impact wrench .. I could also use that rather
than just allen socket in ratchet handle
Make sure that you use a good quality allen key, such as either an Unbrako or Bondhaus make. I would use a T handle allen key as it will allow you to apply downward pressure to keep the key in the socket. Even a slightly slack key will start to round out a soft stainless screw.

As for heating could you get the item in a domestic oven?

John H
l***@gmail.com
2016-12-08 17:04:29 UTC
Permalink
Post by rick
I need to undo 4 x CSK stainless steel screws 3/8x24 UNF
These are screwed into 7000 series anodized billet aluminium.
Fixed by a Loctite (or similar) thread lock
The heads are imperial allen socket.
From past experience I know that even non-Loctite ones can be difficult
to remove, the screws being stainless are relatively soft and they will
round out easily.
Any thoughts over best approach .... I could leave a soak in Plus-gas
penetrating oil, but unsure if that will help .... or I could apply heat.
If the latter then how much to help break Loctite, without damaging
anodized finish or softening screw. .... I have a micro propane torch so
could apply localised heat ...
I also have a pneumatic impact wrench .. I could also use that rather
than just allen socket in ratchet handle
l***@gmail.com
2016-12-08 17:10:57 UTC
Permalink
Post by rick
I need to undo 4 x CSK stainless steel screws 3/8x24 UNF
These are screwed into 7000 series anodized billet aluminium.
Fixed by a Loctite (or similar) thread lock
The heads are imperial allen socket.
From past experience I know that even non-Loctite ones can be difficult
to remove, the screws being stainless are relatively soft and they will
round out easily.
Any thoughts over best approach .... I could leave a soak in Plus-gas
penetrating oil, but unsure if that will help .... or I could apply heat.
If the latter then how much to help break Loctite, without damaging
anodized finish or softening screw. .... I have a micro propane torch so
could apply localised heat ...
I also have a pneumatic impact wrench .. I could also use that rather
than just allen socket in ratchet handle
Why not try connecting a variable voltage power supply to the screw and billet and slowly increase the voltage so that the screw temperature increases (if there is some resistive continuity). Make a handle so that a torque can be applied during the heating process.
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