scope:

FOREWORD

These specifications were prepared by the A.P.I. Committee on the Standardization of Rig Irons.

In January, 1937, this Committee was merged with the Institute's Committee on the Standardization of Standard Rigs and Derricks, under the latter name, and subsequent revisions of this Specification were prepared by the merged Committee. The 1st to 7th editions, inclusive, of this specification were numbered as "A.P.I.Stds.No.6" in the present (8th) edition, this was changed to "A.P.I.Stds.No.-A'.

In formulating these dimensional standards, the Committee worked along the following lines:

FIRST-

Complete interchangeability between manufactures for parts requiring frequent replacement. This specification should be carefully studied by the purchaser so that the degree of interchangeability permitted is well understood. Certain parts are completely interchaeable and others are interchangeable only as complete units. For example jack post boxes are interchangeable only as a complete unit, since the jack post box cap of one manufacturer may not interchange with the lower half of another due to slightly different designs.