In the interest of safety, get a new chair. You cannot rely on commonly available epoxies (or other adhesives) to take the place of a weld on such a high stress joint especially since the available surface area for the joint is small.
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[Request] Looking for a durable office chair replacement base.
Better Office Chair Base
In the interest of safety, get a new chair. You cannot rely on commonly available epoxies (or other adhesives) to take the place of a weld on such a high stress joint especially since the available surface area for the joint is small.
If you like the chair and it is comfortable, you can replace the mechanism. Measure the distance between the holes and then look for a swivel chair mechanism to match.
If you don't particularly like the chair, just get a new chair.
Do not try to fix the actual component. It won't last.
Ok, I did it.
Just dumped some WD-40 and let it soak for 1 minute, then I grabbed my good ol' hammer (I don't have a rubber mallet) and started gently but commitedly striking the edge of the post, with the chair turned upside down, while I grabbed any of the star's legs. It slipped off and then I just hammered its way in into the new post, good as new.
I've had mixed results with using a rubber mallet and penetrating oil to separate friction locked cylinders. Some of them came apart freely, others wouldn't budge.
If your broken base is plastic you can destructively remove it by cutting ~90% through with a hacksaw on two sides and then using a hammer and chisel to split it apart. You don't want to cut into the cylinder itself, so I'd recommend against any sort of rotary cutter.
I've seen suggestions elsewhere to use a large pipe wrench to torque it free; but the one time I tried that I ended up only being able to tighten it enough to scratch the hell out of the surface but not break it loose.
I have an office chair I like that I went through a lot of effort to find. (It's similar to another chair I had used before for almost 20 years) I've replaced the base before because the old one's wheels snapped. (After around 5-6 years) Two years later, this new base (B09K67YQW4 on Amazon) broke now too in the same way. I'm incredibly frustrated after a very stressful week in a very stressful point in my life. I'm just looking for a base replacement for an office chair that is built to last. It was huge struggle to get the old base off for the first replacement and having to do it again is already driving me up the wall in insanity.