I am putting some all grain equipment together and recently bought a slew of fittings from bargainfittings.com . I had the bulkheads welded on to my kegs and was ridiculously excited to put it all together. But when screwing in the nipples and etc into the bulkheads, I get only a thread or two in before they lock. Is this normal??? I noticed a little slag on one of them so I took it back to the welder and he "threaded" them back using some tool. Still same problem remains! Thoughts, solutions?