You should have had the threads chased after the powder coating... Also it pays to blast a frame before coating as the rough uniform surface it leaved behind makes for a really even coat. A smooth frame isn't as good of a surface... In my limited experience that is what I have gathered, it may depend on the coater as well.
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1 Super Record bike, 1 Nuovo Record bike, 1 Pista, 1 Road, 1 Cyclocross/Allrounder, 1 MTB, 1 Touring, 1 Fixed gear