Page 685 - Yamawa_European_Catalogue_YEU21

12. Recommended drill sizes for tapping internal UN and UNJ threads

Intro

SP

SL

PO

UNC/UNF (ANSI B 1.1) UNJC/UNJF (SAE AS8879D)
Minor diameter Minor diameter
Size GH* tap class suitable for GH* tap class suitable for
D1 Drill size D1 Drill size
2B thread tolerance 3B thread tolerance ST
Max. Min. Max. Min.
No. 2 -56 UNC/UNJC 1.871 1.695 1.80 GH2 1.859 1.743 1.81 GH1 GH2
No. 2 -64 UNF/UNJF 1.912 1.756 1.85 GH2 1.902 1.799 1.86 GH1 GH2
No. 3 -48 UNC/UNJC 2.146 1.941 2.10 GH2 2.136 1.999 2.10 GH1 GH2
ROLL
No. 3 -56 UNF/UNJF 2.197 2.025 2.10 GH2 2.189 2.073 2.10 GH1 GH2
No. 4 -40 UNC/UNJC 2.385 2.157 2.30 GH2 GH3 2.392 2.228 2.30 GH1 GH2
No. 4 -48 UNF/UNJF 2.458 2.271 2.40 GH2 2.466 2.330 2.40 GH1 GH2
No. 5-40 UNC/UNJC 2.697 2.487 2.60 GH2 2.722 2.558 2.60 GH1 GH2
CARBIDE
No. 5 -44 UNF/UNJF 2.740 2.551 2.70 GH2 2.763 2.614 2.70 GH1 GH2
No. 6 -32 UNC/UNJC 2.895 2.642 2.80 GH3 GH4 2.938 2.734 2.85 GH2 GH3
No. 6-40 UNF/UNJF 3.022 2.820 2.90 GH2 3.053 2.888 3.00 GH1 GH2
No. 8-32 UNC/UNJC 3.530 3.302 3.40 GH3 GH4 3.599 3.394 3.50 GH2 GH3
No. 8-36 UNF/UNJF 3.606 3.404 3.50 GH3 3.662 3.480 3.60 GH2 GH3 LONG
No. 10-24 UNC/UNJC 3.962 3.683 3.90 GH3 GH5 4.064 3.795 4.00 GH2 GH3
No. 10-32 UNF/UNJF 4.165 3.963 4.10 GH3 GH4 4.254 4.054 4.20 GH2 GH3
No. 12-24 UNC/UNJC 4.597 4.344 4.50 GH3 4.704 4.456 4.60 GH2 GH3
HAND
No. 12-28 UNF/UNJF 4.724 4.496 4.60 GH3 4.815 4.603 4.70 GH2 GH3
TAPS
1/4-20 UNC/UNJC 5.257 4.979 5.10 GH3 GH5 5.387 5.114 5.30 GH2 GH3
1/4-28 UNF/UNJF 5.588 5.360 5.50 GH3 GH4 5.661 5.467 5.60 GH2 GH3
5/16 - 18 UNC/UNJC 6.731 6.401 6.60 GH3 GH5 6.832 6.564 6.70 GH2 GH3
5/16 - 24 UNF/UNJF 7.035 6.782 6.90 GH3 GH4 7.109 6.907 7.00 GH2 GH3
EG (STI)
3/8-16 UNC/UNJC 8.153 7.798 8.00 GH3 GH5 8.255 7.979 8.10 GH3
3/8-24 UNF/UNJF 8.636 8.382 8.50 GH3 GH5 8.679 8.494 8.60 GH2 GH3
7/16 - 14 UNC/UNJC 9.550 9.144 9.40 GH4 GH5 9.639 9.348 9.50 GH3
7/16 - 20 UNF/UNJF 10.033 9.729 9.90 GH3 GH4 10.083 9.876 10.00 GH2 GH3 SPECIAL
THREADS,
1/2-13 UNC/UNJC 11.023 10.592 10.90 GH4 GH5 11.094 10.798 11.00 GH3
GAUGES
1/2-20 UNF/UNJF 11.607 11.329 11.50 GH3 GH4 11.661 11.464 11.60 GH3
9/16 - 12 UNC/UNJC 12.446 11.989 12.20 GH4 12.481 12.228 12.40 GH3
9/16 - 18 UNF/UNJF 13.081 12.751 12.90 GH4 13.121 12.914 13.00 GH3
THREAD
5/8-11 UNC/UNJC 13.868 13.386 13.60 GH4 GH5 13.903 13.628 13.80 GH3
MILLS
5/8-18 UNF/UNJF 14.681 14.351 14.50 GH4 GH5 14.701 14.501 14.60 GH3
3/4-10 UNC/UNJC 16.840 16.307 16.60 GH4 GH5 16.880 16.577 16.70 GH3
3/4-16 UNF/UNJF 17.678 17.323 17.50 GH4 GH5 17.721 17.506 17.60 GH3
DIES
* The most suitable GH tap class to cut accurate 2B, 3B (UNJ) and 2B oversized internal threads tolerance, depends on application conditions and work-piece materials.
Yamawa GH class system off ers a wide range of alternative tap classes allowing each customer to select the most suitable one according to application requirement.

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