I have an easy arm chair that I bought from Ikea. Recently its extra-long-screw that used to be on the sides of the chair got loosened somehow. I tried to tight it by force but it is like super loose and it seems like there used to be something that holds the screw to the chair. How can I tighten it? The screw used is given below:
That's a Poang.
The longer bolts (not screws) need a nut that has probably fallen out and got kicked under the sofa
The shorter bolts, used at the top of the armrest, probably screw into a threaded insert.
If this is problematic you can probably fit a T-nut (likely to be a metric thread)
While you are fixing this, you should tighten up the other bolts (as Ikea advise you to do periodically) or apply some non-permanent thread-lock fluid.
I have a couple of Poang disassembled in my garage, so I may be able to find out more later.