12. 15. Bored hole size before tapping ( for thread cutting ) 12.

■ for Unified Threads ■

Unit : mm

Minor diameter of internal threads (D ) Bored hole size Minor diameter of internal threads (D ) Bored hole size

1 1 Size Size ( ref.) ( ref.)

1.27 13.8 1.54 14.60 1.58 14.92 1.83 16.7 1.87 17.59 2.09 17.89 2.15 19.6 2.33 20.6 2.41 21.06 2.64 22.5 2.69 23.5

2.83 S 23.7

2.97 24.24

  • The figures listed above are according to the data provided by helical coil wire insert manufacturers.

3.47 25.2 3.55 25.6

103.8926.6
104.1227.30
124.5328.4
124.6728.8
124.7829.8

5.19 30.47 5.53 30.9 5.64 32.0

166.6533.0
166.9733.65
167.2234.1

8.07 35.2 8.57 36.2

8.8136.82
169.538.3
169.9639.3
1610.2940.00

10.9 39.6 11.54 41.5 11.88 42.5

1612.34.545.4
1613.0047.9
1613.3248.9
  • The recommended tap drill sizes indicated above are for ANSI B1.1 Class 2B UNC, UNF, UNEF, UN & UNS threads.
  • D1: Minor diameter of JIS Class 2 internal thread.
  • Whitworth Threads have been eliminated from JIS.
  • Marked sizes are in accordance with BSW.