Fastening nut for plastic gates 1 1/2″

01 · THE SIZE

The 49 is millimetres of thread, not a size number

This is the mix-up that reaches us: somebody measures the thread on their gate, gets 21 mm and looks for this nut. It will not do. In this naming the larger number is the outside diameter of the thread in millimetres, so 40/49 is a thread of almost five centimetres. A 21 mm gate is another calibre and takes its own nut. Choose by the number on the gate, not by the hole in the tank.

02 · THE TIGHTENING

Plastic: by hand, and no further

The hexagon is there for your fingers, not for a spanner. With a tool you strip the thread or split it at a corner, and a split nut holds one day and lets go the next. The underlying mistake is usually a different one: when it weeps at the collar the reflex is to tighten harder, when what needs checking is the gasket, which is the part that seals. The nut only applies force.

03 · THE ACCESS

It goes on from inside, with the tank empty

Here is the practical detail people forget when ordering it: this part screws on from the inside, so your arm has to go in. On a wide-mouthed settling tank that is comfortable; on a narrow-mouthed drum, measure before you count on it. And do it with the vessel empty and dry: changing a nut with honey inside means doing the job twice.

04 · BEFORE YOU BUY

Check the profile of your gasket while you are in there: if the nut was cracked, the gasket has probably come out crushed from the same fight.