Pub type C02 bottle regulator has a plain nut that screws ON TO the thread
http://www.ebay.co.uk/itm/Co2-Gas-Re...em256923 191f
Industrial big bottle type regulator has a CONE SHAPED fitting the screws IN TO the bottlehttp://www.ebay.co.uk/itm/ARGON-GAS-WELDING-REGULATOR-TWIN-2-GAUGE-SINGLE-STAGE-/190533461764?pt=LH_DefaultDomain_3&hash=item2c5cad e704
You can also get a brass adaptor to make the industrial regulator fit the pub bottle if you can find them.... It's also worth using some ptfe tape on the adaptor thread to make it gas tight instead of trying to over tighten the thread.