Old flat head screw removal...

[Minkeycat]

I have to remove an old door to get new flooring down.
Can anyone give me any tips on how to remove the old screws from the hinge? They're old, flat head screws that have been in for decades and painted over multiple times and simply won't budge. Access to them isn't great either. The screwdriver requires so much pressure that I'm afraid it's going to slip and take a gouge out of the frame. I've been told to put the screwdriver in the slot of the screw and whack it with a hammer but that hasn't worked. If anyone has another solution, I'd really welcome it.
Many thanks.

 

[paulc]

Scrape the paint away from around the screw head and clean out the slot thoroughly. If need be, use an old chisel to get rid of the last trace of paint in the slot. If you have one, an impact driver with a well fitting bit should shift the screw. Failing that, a decent, good quality screwdriver. Make sure that it is a snug fit in the slot and the right size.

 

[CliffordPope]

Use the jagged end of a broken hacksaw blade to clean out as square-sided and deep a slot as you can. If the slot is worn then it's worth spending a lot of time excavating the metal of the screw head. Use a screwdriver with the widest and thickest blade that will fit in the slot, having ground the blade perfectly square so that it bottoms in the slot with no movement. Choose a screwdriver with a grip that is matched to your own fist size. Lean very hard on the end of the screwdriver with all your weight, giving an extra shove at the moment you twist the blade.
Say to yourself "It will move!" as you concentrate your efforts. As any karate expert will tell you, it's your attitude of mind, the intense application of your thoughts, as much as having perfectly adjusted tools.

Leave the hardest screw until last and try hitting the hinge sideways to break the rust/paint grip.

 

[Feltwell]

All good advice.

If the slot in the screw head is completely mullered already, you can cut a new one at 90 degrees with a Dremel, if you have one - but - you'll almost certainly wreck the hinge doing it.

 

[MatthewC]

There is probably paint under the edge of the screw head; if so, try heating it gently (e.g. with a wallpaper stripper heat gun) to soften the paint before doing the above.

 

[Minkeycat]

Ta daa! Many thanks all. I've done it! Wow. It took ages.
A combination of all methods worked. I think finding a bigger screwdriver with a better grip was probably key along with investing more time clearing out the low cupboard behind the door so that I could squeeze myself in and get to a decent angle and then twist and shove and apply positive mental attitude etc. One of the screws was bent but slowly, slowly catchy monkey applied to that.

 

[fernicarry]

Multi-tool with a metal bit into the slot works well. Cleans out the paint and cuts a deeper slot in one go. I think the vibration also helps break the threads free.

Worked a treat when I was taking off lots of window pulleys some of which were very rusty and impossible to get any force onto from the top of the step ladders.

Then Molegrips on the head once you get it going enough to get some purchase.