I just use my air chisel to tighten them.Just the opposite of gettin it loose.That and they turn to the right so they pretty much self tighten as the pump turns.Just make sure its threaded all the way down.Had one at the shop that wasnt tightened tight by a tech.After it ran for a while to open the stat.I tried to tighten it with the <Tool> thats made to tighten them.It was already tight.I never used the proper tool for them.Just my air chisel.Rocky