Abstract: In one aspect of the invention a method of manufacturing a thin wall isogrid casing by a chip machining process comprises the steps of: positioning a substantially cylindrical casing (10) on a support (20); the support having a substantially continuous cylindrical support surface (22) engaging at least part of the inner or outer surface of the casing; and machining a plurality of recessed pockets in the said inner or outer surface of the casing opposite the surface engaged by the said support; whereby the support reacts loads acting on the casing by the chip machining tool during machining to minimise distortion of the casing and tearing of the pockets being formed. With this method isogrid pockets (14) can be chip machined, by drilling and/or milling etc, with pocket wall thicknesses of less that 1 mm.

Abstract: In one aspect of the invention a method of manufacturing a thin wall isogrid casing by a chip machining process comprises the steps of: positioning a substantially cylindrical casing (10) on a support (20); the support having a substantially continuous cylindrical support surface (22) engaging at least part of the inner or outer surface of the casing; and machining a plurality of recessed pockets in the said inner or outer surface of the casing opposite the surface engaged by the said support; whereby the support reacts loads acting on the casing by the chip machining tool during machining to minimise distortion of the casing and tearing of the pockets being formed. With this method isogrid pockets (14) can be chip machined, by drilling and/or milling etc, with pocket wall thicknesses of less that 1 mm.