“Example of Use” for Cross reference and data:
Flush Jointed Casing is supplied with integral pin and box thread together with a much heavier wall section that Flush Coupled Casing. Flush Jointed Casing makes up flush on the inner and outer walls of the casing. Both internal and external mating shoulders butt against the threaded portion thus providing twice the contact area of Flush Coupled Casing and preventing the threads from climbing under heavy torque loads. Flush Coupled Casing is heavier than its flush coupled equivalent.

BS879 Standard Water Well Casing, the most popular is flush butt jointed casing incorporating square thread system supplied from 4 ½” to 30” diameter, in any combination of lengths. Alternative to screwed and coupled casing systems can be supplied to BS879 specification as required.

API15A Screwed and Coupled Water Well Casing. This standard makes use of the existing oil field standard casing sizes. It is recommended by BS879 as an alternative to their screwed and coupled casings, as a larger range of sizes and wall thicknesses are available.