Machine Screw Size

Number of Threads Per Inch

Minor Dia.

Tap Drills

Clearance Hole Drills

Aluminum, Brass & Plastics

75% Thread 

Stainless Steel, Steels & Iron

50% Thread

All Materials

Close Fit

Free Fit

No. or Dia.

Major Dia.

Drill Size

Decimal Equiv.

Drill Size

Decimal Equiv.

Drill Size

Decimal Equiv.

Drill Size

Decimal Equiv.

1-1/4

1.2500

7

1.0747

1-7/64

1.1094

1-5/32

1.1562

1-17/64

1.2656

1-9/32

1.2812

12

1.1478

1-11/64

1.1719

1-13/64

1.2031

18

1.1818

1-3/16

1.1875

1-13/64

1.2031

1-5/16

1.3125

18

1.2443

1-1/4

1.2500

1-17/64

1.2656

1-21/64

1.3281

1-11/32

1.3438

1-3/8

1.3750

6

1.1705

1-7/32

1.2187

1-17/64

1.2656

1-25/64

1.3906

1-13/32

1.4062

12

1.2728

1-19/64

1.2969

1-21/64

1.3281

18

1.3068

1-5/16

1.3125

1-21/64

1.3281

1-7/16

1.4375

18

1.3693

1-3/8

1.3750

1-25/64

1.3906

1-29/64

1.4531

1-15/32

1.4688

1-1/2

1.500

6

1.2955

1-11/32

1.3437

1-25/64

1.3906

1-33/64

1.5156

1-17/32

1.5312

12

1.3978

1-27/64

1.4219

1-7/16

1.4375

18

1.4318

1-7/16

1.4375

1-29/64

1.4531

1-9/16

1.5625

18

1.4943

1-12

1.500

1-33/64

1.5156

1-37/64

1.5781

1-19/32

1.5938

1-5/8

1.625

18

1.5568

1-9/16

1.5625

1-37/64

1.5781

1-41/64

1.6406

1-21/32

1.6562

1-11/16

1.6875

18

1.6193

1-5/8

1.6250

1-41/64

1.6406

1-45/64

1.7031

1-23/32

1.7188

1-3/4

1.750

5

1.5046

1-9/16

1.5625

1-5/8

1.6250

1-49/64

1.7659

1-25/32

1.7812