Standard Tap & Drill Sizes
American Std. and Unified Form Threads

Tap Drill Size is approximately 75% Thread
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or click here >>> for HUGE 10 PAGE - Expanded Tap & Drill Chart:
includes USS, SAE, METRIC, PIPE SIZES 
& PILOT DRILL RECOMMENDATIONS IN HARD & SOFT WOOD ALSO

Thread Drill   Thread Drill   Thread Drill
0-80 3/64   1/4-20 7   1-12 59/64

1-64

53

  1/4-28 3   1 1/8-7 63/64

1-72

53

  5/16-18 F   1 1/8-12 1-3/64
2-56

50*

  5/16-24 I   1 1/4-7 1-7/64
2-64 50   3/8-16 5/16   1 1/4-12 1-11/64
3-48 47*   3/8-24 Q   1 3/8 -6 1-7/32
3-56.  45*   7/16-14 U   1 3/8-12 1-19/64
4-40 43   7/16-20 25/64*   1 1/2 -6 1-11/32
4-48 42   1/2-13 27/64   1 1/2-12 1-27/64
5-40  38*   1/2-20 29/64   1 3/4 -5 1-9/16
5-44 37   9/16-12 31/64   2" - 4 1/2 1-25/32
6-32 36   9/16-18 33/64   2 1/4-4 1/2 2-1/32
6-40 33   5/8-11 17/32   2 1/2 - 4 2-1/4
8-32 29   5/8-18 37/64   2 3/4 - 4 2-1/2
8-36 29   3/4-10 21/32   3" - 4 2-3/4
10-24 25   3/4-16 11/16   3 1/4-4 3 "
10-32 21   7/8-9 49/64   3 1/2-4 3-1/4
12-24 16*   7/8-14 13/16   3 3/4-4 3-1/2
12-28 14*   1" -8 7/8   4" - 4 3-3/4
      1" -14 15/16      

*SOME SOURCES SUGGEST THE NEXT SIZE SMALLER THAN THESE SIZES.    USE THE
10pg.
Ex
panded Tap & Drill Chart
TO FIND OUT THE NEXT / ALTERNATE SIZE SMALLER.