The office chair I use in my apartment has had a broken gas cylinder for a while now. I couldn't adjust the height of the chair, as soon as I sat down, it was at its lowest adjustment. It also won't stay down. Every time I stand up it springs back to its maximum extension. This got annoying pretty quickly, so I fixed this problem temporarily by tying some paracord around the frame of one of the arms and the base of the chair, this kept the chair locked in its lowest position.
One of the things I got over the holidays was a new gas cylinder. I was eager to replace it, except most of the replacement procedures call out a pipe wench which I didn't have. The cylinder press fits into both the base of the chair and the seat bottom. On some models the piston can be hammered out from both the top and the bottom, but on my chair the top of the piston wasn't exposed, even if the chair bottom was removed from the metal mount. I wasn't about to buy a $20 pipe wrench to repair a chair worth less than that, so I had to improvise. I tried my channellocks first to no avail.
I remembered I had bought some half inch diameter tool steel earlier in the year (I was thinking about making my own engraving tools) that was going unused. My drill bit set conveniently goes up to a half inch drill, so naturally, I started drilling. I drilled a pilot hole first, and then did a size between my pilot and the 1/2 inch bit, before finally drilling the hole to its final size.
After the hole was drilled, I was able to insert the steel rod into the hole and rotate. Worked a charm! Now I have a perfectly functional chair again.
If you're going to go this route, I would suggest not doing it in your kitchen. The metal shavings are difficult to hunt down and pick out of the kitchen mats. -- Also, anticipate some gas release from the inside of the cylinder.