DRILL SIZE FORMING TAPS
P
P
P
55°
60°
60°
ISO Metric coarse thread DIN 13
ISO Metric fine thread DIN 13
Whitworth pipe thread EN - ISO 228
Pitch [mm]
Drill size [mm]
Pitch [mm]
Drill size [mm]
Drill size [mm]
Pitch [TPI]
M
MF
G
M 2
0,4
1,85 ± 0,03
M 3
0,35
2,85 ± 0,03 3,80 ± 0,03 4,80 ± 0,03 5,65 ± 0,03 7,55 ± 0,05 9,55 ± 0,05 9,40 ± 0,05 11,55 ± 0,05 11,40 ± 0,05 11,30 ± 0,05 13,40 ± 0,05 13,30 ± 0,05 15,30 ± 0,05 17,30 ± 0,05 19,30 ± 0,05
G 1/8"
28 19 19 14 14 11
9,25 ± 0,05 12,50 ± 0,05 16,00 ± 0,05 20,00 ± 0,05 25,50 ± 0,05 32,00 ± 0,05
2,5
0,45 2,30 ± 0,03
4 5 6 8
0,5 0,5
1/4" 3/8" 1/2" 3/4"
3
0,5 0,6 0,7 0,8
2,80 ± 0,03 3,25 ± 0,03 3,70 ± 0,03 4,65 ± 0,03 5,55 ± 0,05
3,5
0,75
4 5 6 8
1 1
10 10 12 12 12 14 14 16 18 20
1"
1
1,25
1,25 7,40 ± 0,05
1
10 12 14 16 18 20 24 27 30
1,5
9,30 ± 0,05
1,25
1,75 11,20 ± 0,05
1,5
2 2
13,10 ± 0,05 15,10 ± 0,05 16,90 ± 0,05 18,90 ± 0,05 22,70 ± 0,05 25,70 ± 0,05 28,45 ± 0,05
1,25
1,5 1,5 1,5 1,5
2,5 2,5
3 3
3,5
P
P
60°
60°
Unified coarse thread UNC ASME - B1.1
Unified fine thread UNF ASME - B1.1
Pitch [TPI]
Drill size* [mm] 3,80 ± 0,03 4,35 ± 0,03 5,00 ± 0,03 5,80 ± 0,03 7,30 ± 0,05 8,80 ± 0,05 10,30 ± 0,05 11,80 ± 0,05
Pitch [TPI]
Drill size* [mm] 3,85 ± 0,03 4,45 ± 0,03 5,10 ± 0,03 5,95 ± 0,03 7,45 ± 0,05 9,05 ± 0,05 10,55 ± 0,05 12,15 ± 0,05
D
D
Nr. 8
32 24 24 20 18 16 14 13
Nr. 8
36 32 28 28 24 24 20 20
Nr. 10 Nr. 12
Nr. 10 Nr. 12
1/4"
1/4"
5/16"
5/16"
3/8"
3/8"
7/16"
7/16"
1/2" 5/8" 3/4"
1/2" 5/8" 3/4"
11 14,85 ± 0,05 10 17,90 ± 0,05
18 15,25 ± 0,05 16 18,35 ± 0,05
Other drill sizes = theorical flank diameter + pitch/5
In order to obtain the requested tolerance, the formation of a complete internal thread and guarantee the tap tool life, it is important to respect the drill hole diameters and their tight tolerances. The core diameter of the internal thread obtained by forming is not only a function of the drill hole diameter but also depends on the workpiece material properties. For this reason the tolerance on the core diameter is 7H compared to 6H for cutting taps. For more detailed information see the DIN 13-50 standard.
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