I need to remove an aluminum knob from a radio, but the Allen setscrew
is stuck solid.

I've tried:

-- WD-40
-- Kroil
-- an Allen wrench with a long handle (bent handle)
-- an Allen 1/4" drive socket (twisted the Allen part)
-- blocking up the knob with rubber blocks and beating on the Allen
wrench while turning
-- heating the Allen wrench with a heatgun while engaged with the
setscrew and turning
-- heating the Allen wrench to 450 degrees and then inserting it into
the setscrew and turning

All this and the bloody thing is still stuck solid. As a last resort
I know I can drip 1-mole nitric acid into the hole, which would eat
the steel setscrew and leave the aluminum relatively untouched. This
I have done on aluminum car engines with snapped-off manifold bolts
and it works great.

However, I can think of a bunch of ways this could go wrong when
applied to a rare radio.

I would greatly appreciate any ideas.

Thank you.

73,
Jeff
N6MNI

Jeff wrote:
I need to remove an aluminum knob from a radio, but the Allen setscrew
is stuck solid.

Go to your local auto parts store and get a reverse screw drill bit.
Drill the thing out... it will probably come out from the action of
the bit long before you get drilling toward the shaft.

-- WD-40

I don't know what makes people think WD-40 acts as a penetrating oil.
It's not one. Kroil and PB Blaster are penetrating oils and they can
sometimes work although they are not as effective on steel/aluminum
sticking as steel/steel.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Jeff" wrote in message
...
I need to remove an aluminum knob from a radio, but the
Allen setscrew
is stuck solid.

I've tried:

-- WD-40
-- Kroil
-- an Allen wrench with a long handle (bent handle)
-- an Allen 1/4" drive socket (twisted the Allen part)
-- blocking up the knob with rubber blocks and beating on
the Allen
wrench while turning
-- heating the Allen wrench with a heatgun while engaged
with the
setscrew and turning
-- heating the Allen wrench to 450 degrees and then
inserting it into
the setscrew and turning

All this and the bloody thing is still stuck solid. As a
last resort
I know I can drip 1-mole nitric acid into the hole, which
would eat
the steel setscrew and leave the aluminum relatively
untouched. This
I have done on aluminum car engines with snapped-off
manifold bolts
and it works great.

However, I can think of a bunch of ways this could go
wrong when
applied to a rare radio.

I would greatly appreciate any ideas.

Thank you.

73,
Jeff
N6MNI

Don't know a sure cure other than drilling out the set
screw. Heating the set screw will make things worse by
expanding the screw. heating the knob may help. Also, I've
found that Liquid Wrench works sometimes where WD-40 does
not. It may take a week or two for the oil to penetrate. Put
a new application on every day.
Aluminum tend to gall, this may have happened here. The
result is pretty tight sticking. If you succeed in removing
the screw the new one should have a bit of anti-galling
compound on it. I think you can get this at most hardware
stores.


--

--
Richard Knoppow
Los Angeles
WB6KBL

Jeff wrote in news:232aaf2e-ca5b-4e62-83c2-
:

heating the Allen wrench to 450 degrees and then inserting it into
the setscrew and turning


You heated the wrong thing. What you should heat is the knob trying not to
heat the setscrew in the process.

If you can expand the knob even a little bit by heating, the setscrew is
more likely to come out.

I would greatly appreciate any ideas.

Thank you.

73,
Jeff
N6MNI

Jeff,

Have you tried freezing it? I don't know how large the rest of
whatever it is attached to is and, thus, whether you can put it in a
freezer, but freezing metals generally causes them to shrink (heating
causes them to expand).

Machine shops sometimes freeze press-fit bushings before attempting to
press them as it makes them a lot easier to press into the bored
holes. Sometimes they will just drop in place and when the assembly
reaches room temperature, they are locked tightly in place.

Barry - N4BUQ

Product Linear Temperature Expansion Coefficient - ?-


(10-6 m/m K) (10-6 in/in oF)
Aluminum 22.2 12.3
Steel 13.0 7.3

from:
http://www.engineeringtoolbox.com/li...ents-d_95.html


Looks like the aluminum will expand greater than the steel when both are
equally heated.


Paul P.

"Paul P" REMOVE paul @ REMOVE ppinyot . REMOVEcom wrote in
message ...

Product Linear Temperature Expansion Coefficient - ?-


(10-6 m/m K) (10-6 in/in oF)
Aluminum 22.2 12.3
Steel 13.0 7.3

from:
http://www.engineeringtoolbox.com/li...ents-d_95.html


Looks like the aluminum will expand greater than the steel
when both are equally heated.


Paul P.
Now, does the expansion of the knob make the hole larger
or smaller? My instinct is that all dimensions get larger,
hence the screw should be looser. Or maybe the answer is
some dry ice or liquid nitrogen. (That's only half kidding).


--

--
Richard Knoppow
Los Angeles
WB6KBL

Now, does the expansion of the knob make the hole larger or smaller? My
instinct is that all dimensions get larger, hence the screw should be
looser. Or maybe the answer is some dry ice or liquid nitrogen. (That's
only half kidding).

Richard Knoppow
Los Angeles
WB6KBL


I think that since the metal shrinks when colder, an inside diameter will
get larger and an outside diameter will get smaller too. It's all
shrinking, not collapsing on itself.

Barry - N4BUQ

It is probably so galled that you won't get it off without having to retap
anyway. Too bad you can't just work around it.

Bummer

On Jan 13, 9:11*pm, "JB" wrote:
It is probably so galled that you won't get it off without having to retap
anyway. *Too bad you can't just work around it.

Bummer



-- heating the Allen wrench with a heatgun while engaged with the
setscrew and turning
-- heating the Allen wrench to 450 degrees and then inserting it into
the setscrew and turning

No wonder the wrench bent ! .. you need to heat the alloy knob with
the heat gun .. as hot as you can get it .. with the hole to the top
so you can drip some thin oil in ... then if you like chill the
wrench ... and have a go ... your lucky the hex key still gets a
grip .. ....

need alloy as hot as possible
screw as cold as possible

slight nip clockwise first may break the bond

G ..