Machinable composite molds for use in making a composite structure. The mold includes a mold body having a tool surface that is shaped to provide the molded surface of the composite structure. The mold body is made up of at least one mold layer composed of a quasi-isotropic material composed of a plurality of randomly oriented fiber bundles or chips impregnated with a resin. The use of randomly oriented fiber chips allows post-cure machining of the mold body.