Could you fit a strap wrench on the upper burr carrier?

Another great suggestion, I think with the right tool it might be easy, but the right tool is not easy to find. I will look for bike maintenance shops.

I have some O2 bottles and CO2 bottles that I use for homebrewing as well. Those might work for cooling down the upper part.

Last thought, just to consider, I have a set of adjustable internal pipe wrenches. If diameter were right, perhaps one of those would work as well...

I tried yesterday to place a 23 wrench inside the grooves and it seems to enter into it nicely. Then I tried to apply a torque to it with another wrench, but the 23 wrench flexes! The thing is stuck very hard, and it's unbelievable, as I did the bad job by hand.

I need to buy a specially long screwdriver in order to separate the grinding mechanism from the case, then I will try to get some help from some workshop with the right tools.

I am more and more considering buying a hand-grinder for my Moka - decaffeinated needs. But I did not give up the idea of salvaging my MDF, although it certainly will require time.

Yesterday I manage to eliminate the visible teflon tape, and I also flooded the inner part (where the beans go) with WD-40 hoping that it will penetrate from the inside as well. For the moment, no progress.

If you have a product available to you called Aero Kroil, its one of the better penetrating oils I've some across. That said I'm not how much help it will be. Whatever you did to get them stuck, you did a great job.

Not sure that soaking the coffee grit is a good idea. It may expand and exacerbate the problem. OTOH, it may soften it to the point where it rolls rather than wedges. Be sure to let us know...

Don't forget that the nut holding the lower burr carrier on the MDF is left hand threaded. If you try to remove it by turning counterclockwise, that will only tighten it up more....