The efficacy of penetrating oil

[Smurfy]

My experience is that until the male and female parts of the thread are moving with respect to each other, penetrating oil doesn't do anything. However, once the corrosion seal is broken, penetrating oil is very helpful, as you can work it along the thread by repeatedly rotating back and forth.

Those who are experienced in working on seized fasteners on cars will know that a hammer can be a great aid to loosening threads. Problem is that on a bike everything is much smaller, and there is a very fine line between loosening and wrecking.

 

[Smurfy]

I have a little portable soldering iron that can be used as a torch and it has saved me many a time. Most metals will expand with heat so if you direct the heat at the nut rather than the bolt, you might get a result. Last time I needed to do this was with a seized pedal. A bit of heat on the crank arm around the thread did the job. I've had more success with heat than penetrating oil.

Aluminium has a larger coefficient of thermal expansion than steel. Cranks are usually made of aluminium, pedal spindles are usually made of steel. When heated, the crank gets larger more quickly than the spindle. Result!

Wikipedia suggests the difference between aluminium and steel is around a factor of two.
https://en.wikipedia.org/wiki/Thermal_expansion#Thermal_expansion_coefficients_for_various_materials

 

[mr messy]

Releasing type agents good for lubing rusty exposed threads but as said above very little penetration unless you can submerge in a container. With experience, more often than not, you can feel if a fastener will loosen or shear. At that point it's the fiery spanner or big persuader and chisel. This is from someone who's used many gallons of wd40

 

[DaveReading]

Slightly off-topic, but the aviation industry would have ground to a halt many years ago had it not been for PlusGas ...

 

[Citius]

Slightly off-topic, but the aviation industry would have ground to a halt many years ago had it not been for PlusGas ...

I agree. Our plane once had to stop in mid air because the pilot had run out of PlusGas.