People have been asking me for ages now why I don't have an overlocker (Americans call it a 'serger'). The reason is not knowing how they worked and it would obviously raise the level of complexity of my life a bit. Not to mention that they're expensive: New ones were a lot more expensive than sewing machines, so I looked at second hand (eBay). Very expensive there too (more than $100).
The tip shop had one last week for $30. Here it is,
The machine was made from 1981 in Japan (I just changed that from "France" - where did I get that from??). Funny, my new favourite machine is from 1891. Anyway, the manual was very clear (got it from singerco.com) so after a good clean I read how to thread it and set the tensions. Also disconnected the knife (the default behaviour is to cut the fabric as it gets fed through) because I'd like to do the cutting. EDIT: Re-enabled the knife - Oh, so handy!
Test fabric was denim and the results were a lovely chain around the edge. Might not use it for every garment but it's a good thing to have if it's needed.