FOREWORD (a) This specification was prepared by the API Committee on the Standardization of Rotary Drilling Equipment. (b) This specification gives final dimensional standards, including gages, for "Regular" (Reg.) and "Full-hole" (FH) rotary, drilling tool joints, and tentative standards for' Internal-flush" (IF) rotary drilling tool joints. These tool joints are identified by the size of the drill pipe on which used. (c) This specification also includes standards on drill collars, grief stems, fishtail bits, rotary hose, piston rods and liners for slush pumps, and brake bands, together with recommended practice on measurement of other items. (d) While this specification is intended to include sufficient dimensions to insure interchangeability, especially as regards threaded connections, many dimensions not essential to interchangeability, such as length of drill collars, are omitted, and when purchasers have preference on such unlisted dimensions, the purchase order should so state. In any Case, in order to avoid misunderstanding and delay, purchasers should signify the type of thread desired, such as "regular" or "full-hole", as well as the size. In many cases optional lengths and diameters are indicated which are obtainable on special order. In such cases the "standard" lengths diameter, or style of thread will be furnished unless the purchaser specifically requests otherwise. The intent of the specification is to permit the use of the monogram on equipment which is interchangeable, and still enable the manufacturer to supply, or the purchaser to obtain, this equipment with other details, not affecting interchangeability, in accordance with usage or specified order. (e) This specification provides for the use of the API monogram on certain material; on other material covered by this specification the monogram is not permitted. Purchasers are urged to inspect material to verify that it is properly marked, and that it meets the specification. Material which is not properly marked, or does not meet the specification, should be rejected. (f) New Sizes of Rotary Drilling Taper Joints: Should any other size of joint than now adopted be required, it shall be the duty of the American Petroleum Institute to develop same, that such might immediately become a standard and when a' new joint is developed every licensed manufacturer will be notified at once. (g) Another specification issued by this Committee is the following: 7: API Transmission Standards. (Covers dimensional standards on keys and keyways, shafting sizes 6" and under in accordance with ASA Standards; also key and keyway dimensions, and shaft diameter tolerances for shafting 4-10 in., incl.; also standards on rotary power chain.)