I have never told anyone at work that I am gay, not even the few I have becomes close friends with. I don't feel the need to "come out" but if they were to ask, I'd probably just say yes. But it's not obvious at all except that I don't have a girlfriend. Sometimes I wish I were camp so people wouldn't assume you were straight.
But growing up as a gay kid and afraid of people finding out, because of my traditional Christian background, I learnt to conceal everything so the floppy wrist does not exist anymore, among other "signs". I have nothing against camp guys - in fact sometimes I am attracted to guys who are a bit flamboyant - but being camp wouldn't be an advantage when you work in the butch industry that is engineering. If you are a dude and you want people to take you seriously on a construction site, you need to throw on the muddy boots and talk like a beer-drinking nose-picking football fan. The workers would even be more sympathetic if you screw up occasionally - after all you are just an ordinary man. But I don't pretend to admire the saucy calendars or the page-three girls when I see them in the site canteen because that's not necessary. And I don't want someone to say to me one day "Hey I thought you were into girls!" and I'd feel like a big liar.
I am not saying being masculine is the only way to survive as a male engineer. And you shouldn't change the way you are if you are comfortable with it. But I want to be known as the bright, hardworking engineer rather than the gay one.