Parts won't screw together anymore

On my second build, I have a blade holder and a choke that will no longer screw together. They screwer together perfectly until I put in the heat sink and then it became very difficult to screw them. Like an idiot, I forced them to together even as they were grinding. Now they will only screw about halfway down before stopping and getting stuck. I could see the the threads had been ground some so I smoothed them with a dremel. I tried wd-40 and also a little bit of vaseline, neither of these helped. I dont mind the screws being exposed aesthetically, it looks kind of cool, but if they don't screw all the way down the heat sink is loose. Anybody have any ideas on how to fix this????

It sounds like originally, you didn't have the heat sink all the way down (was likely hung up on a thread towards the bottom), and then you subsequently messed up the threading (by forcing them, and possibly with the Dremel) and that's why they only stop after a certain point. IF you can get them apart, you may want to make sure you really clean and dry the threads on both pieces, just to remove debris, and you might be able to ask Tim if he could rethread them (charges and shipping would apply, obviously.)

I've gotten them apart. I cleaned them and stuff and can screw a little farther than initially but still not all the way.

A local machine shop could probably clean up the threads if the are damaged. Growing up on the farm we had these thread chasers that were 50 or so tool steel bars with various thread pitches cut into one edge, you would manually run down the threads to repair minor damage... Not sure where you would begin to look for those though.

You could look for a thread file. It's similar to what FenixFire mentioned, but it's a single steel bar with multiple threads on it. Just find the one that is the closest match then use it like a file.