There are certain basic rules you must remember before you start to strip flex or cable for connecting to a plug or appliance or for wiring power or lighting circuits. Remove only sufficient insulation to enable the cores to be connected to the terminals; none of the bared wires should be exposed. Don’t stretch the insulation when stripping or you will weaken the portion remaining on the conductor.Take care not to cut through the insulation of conductors, or through a conductor itself, or you will have to shorten the flex or cable and start again. If you damage a conductor the effective current capacity will be lowered and this could cause overheating. Current capacity will also be reduced if you sever any of the fine strands in a length of flex.
Stripping flex
The two most commonly used flexible cords are circular sheathed and braided circular flex. A third, now largely replaced by circular sheathed flex, is twisted twin non-sheath flex.
Circular sheathed
Measure the length of sheathing to be removed and carefully run a knife round the sheath, making sure not to damage the core insulation. From this point, make a cut along the length of the flex to the end, cutting through to the inner insulation. Remove the sheathing with pliers, leaving the insulated cores exposed. Measure the length of insulation to be removed from each core and carefully take it off with wire strippers. Always twist the bared ends of each core together to ensure there will be no stray whiskers to cause a short circuit when the conductors are inserted in their terminals.
Circular braided
Measure the length of braiding to be removed and cut it off with a sharp knife. Trim off the frayed edges and any textile fillers inside the braid and slip a rubber sleeve over the end to prevent further fraying. Strip the required length of insulation from each core and twist the wires together as before.
Twisted twin
Since this type has no sheathing, you only need to strip insulation and twist the cores together.
Stripping cable
The method for stripping cable is basically the same as for stripping flex, but you must take extra care not to damage the conductors since cable is expensive to replace.
Sheathed
Measure and strip off the required amount of sheathing using a knife and pliers as previously described. Strip off the insulation from each wire and slip a length of green (or green/ yellow) PVC sleeving over the end of the earth wire. With the smallest cables (1.0 and l.5sq mm). double the bared ends to provide greater contact area in the terminals. Cables of 4sq mm and above have stranded conductors and the ends must be twisted together with pliers.
Non-sheathed single core
An example of this is the green/yellow PVC insulated earth cable; simply remove the insulation with wire strippers as described above.