Copper Wire Stranding Data

Strand Construction

• Bunch: Composed of any number of the same diameter wires twisted in the same direction without regard to geometric arrangement of individual strands. Bunch construction offers greater flexibility and lowest cost.
• True Concentric: A central wire surrounded by one or more helically laid wires with lay direction reversed and length of lay increased for each successive layer. True concentric construction offers increased mechanical strength and crush resistance.
• Unilay: Same as true concentric, except that lay direction and length of lay are the same for each successive layer. Normal direction is LHL. Unilay has the smallest diameter and lowest weight of helicallly laid core constructions.
• Rope Stranding: Made up of cabled groups and is generally used for 8 AWG or larger.

Stranding Class Uses

Concentric-lay Conductors
Class B	Power cables.
Class C	Power cables where more flexible stranding than Class B is desired.
Class D	Power cables where extra flexible stranding is desired.
Rope-lay & Bunch stranded Conductors*
Class G	All cables for portable use.
Class H	All cables where extreme flexibility is required, such as for use on take-up reels etc.
Class I	Apparatus cable and motor leads.
Class K	Cords and cables composed of No.30 AWG copper wires.  Stationary service.
Class M	Cords and cables composed of No.34 AWG copper wires. Constant service.