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Conduit fittings: couplers, bushes, boxes and saddlesWhat does a brass bush actually do?

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Once your thread matches the factory thread, it screws into any standard fitting. Tighten fittings up with grips and they stay put "forevermore".

  • Coupler: joins two lengths of conduit. Each thread goes halfway into the coupler, leaving the other half for the next length.
  • Conduit boxes: three are shown here, and lots of other bends and boxes exist.
    • a flat 90° bend box (turns a corner),
    • a tee box (three directions),
    • a through box (straight through, for drawing in or a joint).
    You can drill a box's back to fix it to the wall.
  • Brass bush (ours was 20 mm): screws into a coupler from inside a box to fix the conduit to the box. Useful for boxes and enclosures with a plain hole rather than a threaded spout.
  • Bush spanner: tightening a bush with ordinary grips is awkward because you can only get at one side, so you can buy a special spanner for it.
  • Saddles: fix the conduit run to walls, ceilings or floors so the whole system is secure.
Joining two lengths coupler ½ thread ½ thread conduit conduit Fixing to a box with a brass bush brass bush screwed in from inside the box coupler box wall conduit Tighten with a bush spanner: only one side is reachable
Left: a coupler joins two lengths, each thread going in halfway. Right: the box wall is clamped between the coupler outside and the brass bush inside.
90° bend box turns a corner Tee box three directions Through box straight through front view saddle screws to the wall
The three boxes shown (plan view), and a saddle holding the conduit to a wall. Saddles work on walls, ceilings and floors.

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