90 degree angle in cable tray

A right-angle turn needs the biggest cut of all: at 90 degrees the wedge in the base equals the tray width. On 300 mm tray that is 300 mm each way from the bend line, so 600 mm of opening along the inner edge.

What to cut and where

Marking out starts with the bend line — a line across the base where the run turns. The wedge tip goes on the outer edge, right on that line: no metal is cut there at all. On the inner edge, measure off the line both ways and join those points to the tip — that gives a triangle with a right angle at the apex. The side that ends up inside the turn is cut through its full height; the outer side is left alone and bends by itself.

When two 45s are better

On wide tray a 90 degree cut runs two tray widths long, and the piece needs room to swing. Where a run follows a wall or sits in a tight void, two 45 degree turns are usually easier: each cut is a quarter of the size, the metal folds more readily, and the total angle is the same. On 300 mm tray that is 124 mm per notch instead of 300 mm in one go.

Cutting the lid at the bend

The lid does not get mitred at a bend. On the length before the turn it is cut square across the edge, and the lid of the length after the turn is pushed up against it at 90 degrees — the joint comes out neat and the lid keeps its stiffness. A 45 degree cut is worse for three reasons: the cut is longer, it is easier to wander off the line, and the sharp corner left on the lid lifts at the slightest knock. A straight cut is the whole job here, so set the line out with a square rather than by eye.

Perforated tray

The working does not depend on the perforations, but when marking out keep the bend line off a row of holes: the bridges between them tear at the fold. If the line lands on holes, shift the turn a couple of centimetres along the run.