Adjustable Spanner

You want/need a torque wrench and socket set:

torque wrench and socket set

Which part of the world are you in?

Use a set of proper spanners sized for the cable glands you want to install instead, adjustable spanners can damage cable glands and are generally more difficult to use in confined spaces anyway.

Get the proper tools.

_{Jack - Yes I also sell cable glands.}

The usual worry with adjustables is that they can be used loose & can then damage or round off the nut they are tightening. 2 tools that help prevent this are the Stanley locking adjustable & the Knippex slip joint pliers. The Stanley tool locks onto the nut like a mole wrench & the Knipex tool is like gas pliers but the jaws are always held parallel.