The local brewery uses immersion heaters in the hot liquor tank. This runs at about 78 C so develops a fair amount of limescale. Any idea where we might find a 2 1/4 bsp thread chaser to clean up the threads when replacing elements? (£300 for a "proper" tap is a bit of an investment).
I'd wondered about fabricating something from three or four 5/8 BSW or UNC taps (which also have 11 tpi) on an adjustable or "soft" mandrel.
Tank and bosses are stainless, so hydrochloric acid not a good idea.
(Chief beer taster. I get to check a pint out of every barrel they produce. £50 a week; not much, I know, but it's all I can afford)