Hi Lucas

​Depending on where the screws are located on the typewriter can have a bearing on how to approach really stuck screws. If the screws are in metal with no plastic or rubber close by, a heat gun applied to the area can expand the surrounding metal releasing a bit of the tension holding the screws in place. One other thing to always keep in mind is the direction of thread. Every once in a while, you may come across a left hand threaded screw.

​There are many other methods of removing stuck screws which are employed by mechanics, but these typewriters are a little too delicate for many of these methods. Stuck screws on motorcycle engines can often be loosened with an impact driver. A chisel driven into the edge of a screw head, then angled off will often get a very stubborn screw moving.

On some of the equipment I work on, a seized bolt can be eased out by heating the head almost to red heat and applying candle wax which wicks into the threads and helps loosen the grip. Hope this gives you some ideas,

Sky

You could also try applying a close-fitting screwdriver to the slot, and then rapping the end of the screwdriver handle with a small hammer.  The operative word is rapping - not smashing hell out of it !  The short, smart blow will often shock seized threads into loosening.  This is a typewriter variation on the impact driver that Skywatcher mentions.  As Sky also says, heat can work well.  I have a miniature blowlamp which I use for this, but bear in mind that it can damage rubber, plastic or paintwork, and affect plating.  Something I have heard of, and intend to try soon, is to obtain an old fashioned soldering iron - the kind with a large copper bit that you heat over a gas flame before use.  Heat the soldering iron as hot as you can get it and press the tip onto the screw head.  Much kinder to the surrounding parts I would imagine.  You could also try soaking the part in light machine oil or penetrating oil for several days before your next attempt.  As an amateur, you have the advantage over the professional in that time isn't usually important.  If it takes days to soak in, it really doesn't matter.  You haven't got an impatient customer breathing down your neck  

Re: Electric Soldering Irons.  Readers in other countries would probably astounded to hear that in the UK those giant 300 watt irons have been banned from sale for over 15 years now.  The reason ?  European Union Regulations !  Not wanting to turn this forum into a political rant, but maybe it was petty interferences in our everyday lives and absurd  regulations like this, that made people vote to get out of the EU !

I think it may be to do with limiting power consumption to meet some sort of silly 'green' target.  It is now very difficult to buy an incandescent light bulb here for the same reason.  A couple of years ago they banned the sale of vacuum cleaners over a certain wattage and there was a mad scramble at the shops to buy existing stock before it went.  The latest I hear is that the sale of domestic gas cookers is due to be banned in a few years time.  Maybe if we are out of the EU by then, it won't happen here.  But I wouldn't bet on it !