TM 1-1500-204-23-6 Table  2-16.  Twinsert and Tools Data - CONT Drill Tap Nominal minor Dia.                                                                 Assembled thread after tap Major Dia. Pitch Dia. pitch Dia. size min-max min min-max min - max National Fine Series 6-40 .176- .182 1.998 .1868- .1886 .1543- .1569 10-32 .238- .245 .2670 .2509- .2530 .2103 - .2133 1/4-28 .310- .318 .3379 .3196- .3219 .2732- .2765 5/16-24 .375 - .383 .4150 .3936- .3964 .3395- .3433 3/8-24 .435- .443 .4776 .4561- .4590 .4020- .4059 7/16-20 .514- .526 .5604 .5349- .5383 .4700- .4744 1/2-20 .576- .588 .6231 .5974- .6010 .5325- .5371 Oversize kit part number Twinsert kit part number Nominal size Screw thread insert Screw lock insert Screw thread Screw lock National Coarse Series 4-40 3166-04 3170-04 3174-04 3176-04 5-40 3166-05 3170-05 3174-05 3176-05 6-32 3166-06 3170-06 3174-06 3176-06 8-32 3166-2 3170-2 3174-2 3176-2 10-24 3166-3 3170-3 3174-3 3177-3 12-24 3166-1 --- 3174-1 3177-1 1/4-20 3166-4 3170-4 3174-4 3177-4 5/16-18 3166-5 3170-5 3174-5 3177-5 3/8-16 3166-6 3170-6 3174-6 3177-6 7/16-14 3166-7 3170-7 3174-7 3177-7 1/2-13 3166-8 3170-8 3174-8 3177-8 National Fine Series 6-40 3188-06 3172-06 3175-06 3178-06 10-32 3188-3 3172-3 3175-3 3179-3 1/4-28 3188-4 3172-4 3175-4 3179-4 5/16-24 3188-5 3172-5 3175-5 3179-5 3/8-24 3188-6 3172-6 3175-6 3179-6 7/16-20 3188-7 3172-7 3175-7 3179-7 1/2-20 3188-8 3172-8 3175-8 3179-8 1   Add assembly number to length (e g 3180-04CN + .168). 2-65