Would be lathe worlds Supp for dark heresy work with deathwatch?

I'm not sure what exactly do you mean...

New skills, talents and gear? You'll need to adjust XP cost and some stats, especially if you use Errata stats for weapons, but why not?

Lathe system/other Calyxis forge worlds as a place for Kill-Team mission? It may be interesting. Calyxis Mechanicus and Inquisition have a long history of very delicate relationships.

For human NPCs definitely, though it doesn't add anything really for the actual PCs. Except perhaps the Integrated Weapons rules for Techmarines/Iron Hands.

well, what I meant was can you run lathe worlds with drqthwatch if you don't have dark heresy? Do they use the same rules system, are they interchangeable in terms of rules, characters, gear, etc?

Yes, all games up to Black Crusade used roughly the same ruleset and are pretty much interchangeable. Check in your DW Core Rulebook in the GM section for the whole part about bringing the other games into DW.

I have a hard copy of the DW rules book I bought at my FLGS. So I don't know about RT or DH yet.

Well, I ordered a shiny new copy so I guess FFG will be happy.I like the AM and if I we're to.play DW I would likely take a tech Marine.