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RMP Decimal Equivalent Chart

 

RMP Tap & Drill Sizes
Drill
Size
_____
mm

_____
Decimal
Equiv.
______
  Drill
Size
_____
mm

_____
Decimal
Equiv.
______
Tap
Size

______
Drill
Size

______
Probable
% Thread
_______
  Tap
Size

______
Drill
Size

______
Probable
% Thread
_______
-
-
-
-
80
79
1/64
78
77
-
76
75
74
-
73
72
71
-
70
69
-
68
1/32
-
67
66
65
-
64
63
62
61
-
60
59
58
57
56
3/64
55
54
53
1/16
52
51
50
49
48
5/64
47
-
46
45
44
43
42
3/32
41
40
39
38
37
36
7/64
35
34
33
32
-
31
1/8
30
29
28
9/64
27
26
25
24
23
5/32
22
-
21
20
19
18
11/64
17
16
15
14
13
3/16
12
11
10
9
-
8
7
13/64
6
0.10
0.20
0.25
0.30
0.34
0.37
0.40
0.41
0.46
0.50
0.51
0.53
0.57
0.60
0.61
0.64
0.66
0.70
0.71
0.74
0.75
0.79
0.79
0.80
0.81
0.84
0.89
0.90
0.91
0.94
0.97
0.99
1.00
1.02
1.04
1.07
1.09
1.18
1.19
1.32
1.40
1.51
1.59
1.61
1.70
1.78
1.85
1.93
1.98
1.99
2.00
2.06
2.08
2.18
2.26
2.37
2.38
2.44
2.50
2.53
2.58
2.64
2.71
2.78
2.79
2.82
2.87
2.95
3.00
3.05
3.18
3.26
3.45
3.57
3.57
3.66
3.73
3.80
3.86
3.91
3.97
3.99
4.00
4.04
4.09
4.22
4.31
4.37
4.39
4.50
4.57
4.62
4.70
4.76
4.80
4.85
4.91
4.98
5.00
5.05
5.11
5.16
5.18
.0039
.0079
.0098
.0118
.0135
.0145
.0156
.0160
.0180
.0197
.0200
.0210
.0225
.0236
.0240
.0250
.0260
.0276
.0280
.0292
.0295
.0310
.0313
.0315
.0320
.0330
.0350
.0354
.0360
.0370
.0380
.0390
.0394
.0400
.0410
.0420
.0430
.0465
.0469
.0520
.0550
.0595
.0625
.0635
.0670
.0700
.0730
.0760
.0781
.0785
.0787
.0810
.0820
.0860
.0890
.0935
.0938
.0960
.0980
.0995
.1015
.1040
.1065
.1094
.1100
.1110
.1130
.1160
.1181
.1200
.1250
.1285
.1360
.1405
.1406
.1440
.1470
.1495
.1520
.1540
.1562
.1570
.1575
.1590
.1610
.1660
.1695
.1719
.1730
.1770
.1800
.1820
.1850
.1875
.1890
.1910
.1935
.1960
.1968
.1990
.2010
.2031
.2040
5
4
3
7/32
2
1
A
15/64
-
B
C
D
1/4
E
F
G
17/64
H
I
-
J
K
9/32
L
M
19/64
N
5/16
-
O
P
21/64
Q
R
11/32
S
-
T
23/64
U
3/8
V
W
25/64
-
X
Y
13/32
Z
27/64
-
7/16
29/64
15/32

-
31/64
1/2

-
33/64
17/32
35/64

-
9/16
37/64

-
19/32
39/64
5/8

-
41/64
21/32

-
43/64
11/16
45/64

-
23/32
47/64

-
3/4
49/64
25/32

-
51/64
13/16

-
53/64
27/32
55/64

-
7/8
57/64

-
29/32
59/64
15/16

-
61/64
31/32

-
63/64
1"
5.22
5.31
5.41
5.56
5.61
5.79
5.94
5.95
6.00
6.15
6.25
6.35
6.35
6.53
6.63
6.75
6.75
6.76
6.91
7.00
7.04
7.14
7.14
7.37
7.49
7.54
7.67
7.94
8.00
8.03
8.20
8.33
8.43
8.61
8.73
8.84
9.00
9.09
9.13
9.35
9.53
9.56
9.80
9.92
10.00
10.08
10.26
10.32
10.49
10.72
11.00
11.11
11.51
11.91
12.00
12.30
12.70
13.00
13.10
13.49
13.89
14.00
14.29
14.68
15.00
15.08
15.48
15.88
16.00
16.27
16.67
17.00
17.07
17.46
17.86
18.00
18.26
18.65
19.00
19.05
19.45
19.84
20.00
20.24
20.64
21.00
21.03
21.43
21.84
22.00
22.23
22.62
23.00
23.02
23.42
23.81
24.00
24.21
24.61
25.00
25.00
25.40
.2055
.2090
.2130
.2188
.2210
.2280
.2340
.2344
.2362
.2380
.2420
.2460
.2500
.2500
.2570
.2610
.2656
.2660
.2720
.2756
.2770
.2810
.2812
.2900
.2950
.2969
.3020
.3125
.3150
.3160
.3230
.3281
.3320
.3390
.3438
.3480
.3543
.3580
.3594
.3680
.3750
.3770
.3860
.3906
.3937
.3970
.4040
.4062
.4130
.4219
.4331
.4375
.4531
.4688
.4724
.4844
.5000
.5118
.5156
.5312
.5469
.5512
.5625
.5781
.5906
.5938
.6094
.6250
.6299
.6406
.6562
.6693
.6719
.6875
.7031
.7087
.7188
.7344
.7480
.7500
.7656
.7812
.7874
.7969
.8125
.8268
.8281
.8438
.8594
.8661
.8750
.8906
.9055
.9062
.9219
.9375
.9449
.9531
.9688
.9842
.9844
1.0000
0-80
M1.6x0.35
1-64
M2x0.4
1-72
2-56
2-64
M2.5x0.45
3-48
3-56
4-40
4-48
M3x0.5
5-40
5-44
M3.5x0.6
6-32
6-40
M4x0.7
8-32
8-36
10-24
10-32
M5x0.8
12-24
12-28
M6x1
1/4-20
1/4-28
5/16-18
5/16-24
M8x1.25
3/8-16
3/64
1.25mm
53
1/16
53
51
50
2.05mm
5/64
46
44
42
40
39
38
33
36
33
3.3mm
29
29
25
21
4.2mm
17
15
5mm
7
3
F
I
6.7mm
5/16
71
69
59
72
67
74
70
69
70
69
74
61
70
71
72
72
72
69
68
62
70
69
68
69
73
70
70
70
72
72
67
74
72
3/8-24
M10x1.5
7/16-14
7/16-20
M12x1.75
1/2-13
1/2-20
M14x2
9/16-12
9/16-18
5/8-11
5/8-18
M16x2
3/4-10
3/4-16
M20x2.5
7/8-9
7/8-14
M24x3
1-8
1-12
1-14
1-1/8-7
1-1/8-12
M30x3.5
1-1/4-7
1-1/4-12
1-3/8-6
1-3/8-12
M36x4
1-1/2-6
1-1/2-12
Q
8.4mm
U
25/64
13/32
27/64
29/64
15/32
31/64
33/64
17/32
37/64
35/64
21/32
11/16
11/16
49/64
13/16
53/64
7/8
59/64
15/16
63/64
1-3/64
1-3/64*
1-7/64*
1-11/64*
1-7/32*
1-19/64*
1-1/4*
1-11/32
1-27/64*
71
76
70
65
69
73
65
76
68
58
75
58
76
68
71
74
72
62
72
73
67
61
72
66
75
76
72
72
72
80
72
72
*Reaming Recommended
Pipe Tap Sizes
Tap
Size
_________
Tap
Drill 75%
_______
Form

_______
1/8-27
1/4-18
3/8-18
1/2-14
3/4-14
1"-11 1/2
11/4-11 1/2
11/2-11 1/2
2-11 1/2
1/16-27
1/8-27
1/4-18
3/8-18
1/2-14
3/4-14
1-11 1/2
11/4-11 1/2
11/2-11 1/2
2-11 1/2
11/32
7/16
37/64
23/32
59/64
15/32
11/2
13/4
27/32
C
Q
7/16
9/16
45/64
29/32
1 9/64
1 31/64
1 23/32
23/16
NPSC
NPSC
NPSC
NPSC
NPSC
NPSC
NPSC
NPSC
NPSC
NPT/NPTF
NPT/NPTF
NPT/NPTF
NPT/NPTF
NPT/NPTF
NPT/NPTF
NPT/NPTF
NPT/NPTF
NPT/NPTF
NPT/NPTF
RMP Machining Calculations
SFM = RPM x Dia ÷ 3.82
RMP = 3.82 x SFM ÷
Dia
IPM = IPT x No. Teeth x RPM
IPT = IPM ÷ No. Teeth x RPM
IPR = IPM ÷
RPM
CIM = IPM x WOC x DOC
HP = CIM x UHP

Definitions : SFM-speed feet per minute , RPM-rotations per minute Dia-diameter , IPM-inches per minute , IPT-inches (feed) per tooth , IPR-inches per revolution , CIM-cubic inches of material , IPM-inches per minute , WOC-width of cut , DOC-depth of cut , HP-horsepower , UHP-machinability factor & BHN-brinell hardness (see chart below)

 

Material
__________
BHN
______
UHP
______
Aluminum
Brass
Copper
Gray-Iron
Nod-Iron
Inconel 700
1020
1050
4140
52100
6150
Cast Steel
Stainless
---
---
---
200
225
330
165
225
275
225
375
225
225
.25
.25
.30
.33
.54
1.1
.58
.80
.70
.67
1.3
.62
.73