Is this tap drill chart enough for production work?

It is a fast reference, not a substitute for the drawing, tooling supplier, material requirements, or applicable standards.

Why do different charts sometimes disagree?

Charts can assume different thread engagement, tap type, material, tolerance class, or rounding to available drill sizes.

Shop reference tools

Look up recommended tap drill sizes for UNC, UNF, and metric threads.

Start with the table, then use the related pages for tapping, clearance holes, pilot holes, and printable shop sheets.

Thread	Tap drill	Decimal inch	Millimeters	Working note
#4-40 UNC	#43	0.0890	2.26	Common machine-screw tap size.
#6-32 UNC	#36	0.1065	2.71	Useful for light machine screws.
#8-32 UNC	#29	0.1360	3.45	Check thin material and thread depth.
#10-24 UNC	#25	0.1495	3.80	Coarse #10 machine screw thread.
#10-32 UNF	#21	0.1590	4.04	Fine #10 machine screw thread.
1/4-20 UNC	#7	0.2010	5.11	Common quarter-inch coarse tap.
1/4-28 UNF	#3	0.2130	5.41	Fine quarter-inch tap.
5/16-18 UNC	F	0.2570	6.53	Coarse 5/16 inch tap.
5/16-24 UNF	I	0.2720	6.91	Fine 5/16 inch tap.
3/8-16 UNC	5/16	0.3125	7.94	Common coarse 3/8 inch tap.
3/8-24 UNF	Q	0.3320	8.43	Fine 3/8 inch tap.
1/2-13 UNC	27/64	0.4219	10.72	Coarse half-inch tap.
1/2-20 UNF	29/64	0.4531	11.51	Fine half-inch tap.
M3 x 0.5	2.5 mm	0.0984	2.50	Approximate metric tap drill: major diameter minus pitch.
M4 x 0.7	3.3 mm	0.1299	3.30	Use published chart for production work.
M5 x 0.8	4.2 mm	0.1654	4.20	Common metric coarse thread.
M6 x 1	5.0 mm	0.1969	5.00	Common metric coarse thread.
M8 x 1.25	6.8 mm	0.2677	6.80	Common metric coarse thread.
M10 x 1.5	8.5 mm	0.3346	8.50	Common metric coarse thread.
M12 x 1.75	10.2 mm	0.4016	10.20	Common metric coarse thread.