I'm going to sound like a jerk but hear me out, For one thing, I have a problem using the word " friends" in conjunction with the workplace. From what I've found, the whole workplace and being friends with your co-workers, outside of work causes problems. I know everyone is different but I'll share with you my own experiences, from my younger more naïve days.
I'll try to keep this a concise as I can. One time, about 10 years ago I was drug into some serious BS drama at work. 2 Co-workers whom I considered friends(big mistake!), got into this big ass fight and I got caught in the crossfire. I didn't want to take a side but somehow by default I ended up sort of siding with the person, as much as I tried to stay neutral. There were a few trips into HR, because the other guy started making my life a living hell.
I dealt with this stalemate for a long time, back then, if the economy had not been so bad I would of quit. Luckily, the guy ended up leaving the company along with the other co-worker, plus since then we have had a turn over of people, so pretty much it's forgotten for the most part.
Another time, I got in too deep with this one clique I was apart of, later I found out they were talking s--t about me behind my back, I was kind of stunned to be honest but it was a life lesson I guess, watch what you say and who you say it to at work. I said and shared too much info about myself and it bit me right in the ass. Luckly, like before, all those people are gone now.
I learned after the last time, go to work, make your money, and go home. Now, I am friendly with a handful of people but now I CLEARLY separate work and my personal life. I'm not gonna say I wish I wasn't part of a group anymore but at the same time it's liberating not be, so the latter is the better way to go.
So, I would say I have friendly acquittances at work, however once the day is done and I leave, that's it. I don't bring work home with me anymore. Sorry for the long rant but that's just how I see it.