Co-Worker Friends

"I'm going to have a couple of beers with my coworkers"

...sometimes it's weird saying 'co-worker' especially with some ppl. In some cases, I don't want to use the term 'co-worker'... I'd rather use the term 'friend'.

It's inevitable.

I see these ppl at work five days out of the week. It's bound to happen. Coworkers becoming 'friends'.

But is there a distinction and limits to when you can really become 'close' to work-related ppl?

Just a matter of 'comfortability'.

Definitely can't ask my manager to have a couple of beers after work or be open with very personal private issues.

There are definitely a few ppl I can see myself hanging out with outside of work and knowing we can become 'friends'.

And there are those that I just know I will always term as 'co-worker'.