How do I fasten this expansion bolt?

[Tony2]

The pivot part is 14 mm thick. I tried drilling a 14 mm hole in a plank but the nut won't fit through the hole as it is 16 mm wide. If I drill a 16 mm hole, the outermost part will wobble significantly and the bolt won't hold securely. The wall is a one-inch chipboard, one-inch air, and timber on the innermost part. It is for a water heater.

 

[Allmänobildad]

It is for a water heater.

It is also for a concrete wall. If you have wood in the wall, you should use another fastening method.

 

[Tony2]

It's also for concrete walls. If you have wood in the wall, you should use another fastening method.

They came with the water heater (Biltema's). There's nothing in the manual about any other fastening method. I've probably given up the idea of using the bolts now and plan to use long wood screws that reach into the timber.