Threads

Standard Screw Threads and Tap Drill Sizes

U.S. Machine Screw Standard

No.	Thread	Tap Drill	Clear Drill
0	80	56	52
1	72	53	48
2	56	49	43
3	48	47	39
4	40	44	32
5	40	39	30
6	32	36	28
8	36	29	19
10	32	21	11
12	24	16	2

Machine Screw Diameters

By H. J. Coventry

The Miniature Locomotive, July-August 1954

Machine screws are numbered as distinct from Cap Screws, Bolts, etc, and range usually from #0 to #12. A convenient method of finding the exact diameter if a table is not handy is as follows:

Multiply the number of 13 and add sixty thousandths. The answer will be thousandths.

Examples:

• #0 -- 0 multiplied by 13 equals 0, plus 0.060 equals 0.060
• #3 -- 3 multiplied by 13 equals 39, plus 0.060 equals 0.099
• #5 -- 5 multiplied by 13 equals 65, plus 0.060 equals 0.125
• #10 -- 10 multiplied by 13 equals 0.130, plus 0.060 equals 0.190

External Links

• "Making Scale Hex Head Bolts", Home Metal Shop Club