Screw Pitch Gages English and Metric Screw Pitch Gages 2-1/4-84 PITCHES (INCH) 0.25-11.5 PITCHES (MILLIMETER) Screw pitch gages are among the most useful tools in any mechanics' tool box. They quickly determine the pitch of various threads.These gages consist of a substantial steel case with a number of folding leaves at both ends, each leaf having teeth corresponding to a specific pitch, marked on each leaf. Starrett screw pitch gages are available in a wide range of sizes with different numbers of leaves in various pitch ranges. V, Unified, American National 60º threads Whitworth Standard 55º threads International Metric Standard 60º threads English and metric threads are similar in form, but English threads are described in threads per inch and metric threads by the distance from one crest to the next. All screw pitch gages (except 473 and 476, which have a positive stop design) feature a locking device at both ends of the case, so leaves can be securely locked in position for use. Leaves on most gages have a special narrow design, permitting checking internal threads in nuts, etc., as well as external threads. Various types of Starrett screw pitch gages are illustrated on the following pages, with complete specifications. Formulas American Natational V Thread d = D –1.299 d = D – 1.732 N N D = Outside diameter of tap d = Bottom diameter of tap N = Number of threads per inch 155 484 6 474 NATIONAL FORM SHARP V Starrett Screw Pitch Gages have the tops of the teeth flatted, permitting use of a single gage for either National Form threads or Sharp V threads Screw Pitch Gages Cat. No. EDP No. of Leaves TPI Range Threads per Inch (TPI) Description 155 50588 27 2-1/4–28 2-1/4, 2-3/8, 2-1/2, 2-5/8, 2-3/4, 2-7/8, 3, 3-1/4, 3-1/2, 4, 4-1/2, 5, 5-1/2, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 18, 20, 24, 28 With locking device and 60º center gage 484 67447 28 3-1/2–36 3-1/2, 4, 4-1/2, 5, 5-1/2, 6, 7, 8, 9, 10, 11, 11-1/2, 12, 13, 14, 15, 16, 18, 20, 22, 24, 26, 27, 28, 30, 32, 34, 36 With locking device 6 50035 30 4–42 4, 4-1/2, 5, 5-1/2, 6, 7, 8, 9, 10, 11, 11-1/2, 12, 13, 14, 15, 16, 18, 20, 22, 24, 26, 27, 28, 30, 32, 34, 36, 38, 40, 42 With locking device and 11-1/2 and 27 pipe thread pitches 474 52486 28 4–80 4, 4-1/2, 5, 6, 7, 8, 9, 10, 11, 11-1/2, 12, 13, 14, 16, 18, 20, 24, 27, 28, 32, 36, 40, 44, 48, 56, 64, 72, 80 With locking device and 11-1/2 and 27 pipe thread pitches 332 F ixed G age S t andards