M9 - Basic Thread Dimensions

Property mm Inch
Nominal Diameter 9 0.3543
Pitch (Distance) 1.25 0.0492
Pitch Diameter 8.188 0.3224
Minor Diameter 7.647 0.3011
Thread Height 0.677 0.0267
Addendum 0.406 0.016
Crest (External)
Root (Internal)		 0.156 0.0061
Tap Drill Size
(75% depth)		 7.78 0.306
Lead Angle
(Single Start)		 2.78°
Thread Family Metric Coarse Pitch (MC)
Relevant Standards ISO 68-1, ISO 9651-1, ISO 965-2, ISO 261,DIN 13
Equivalent Inch Thread3/8 - 20 20-UN

For more threading data scroll down, or use the Thread Calculator

Table of Content

M9 Possible Thread Classes

External Threads

Choose tolerance class: 4g, 4h, 6e, 6g, 6h, 8e, 8g, 5g4g, 5h4h, 5g6g, 7g6g, 7h6h, 7e6e, 9e8e, 9g8g

Metric ISO External Thread - Tolerance sketch

Internal Threads

Choose tolerance class: 4H, 5H, 5G, 6H, 6G, 7H, 7G, 8G

Metric ISO Internal Thread - Tolerance sketch

M9 4g (External)

* Permisable values for thread Class 4g

# Description Value (mm) Value (Inch)
es Allowance 0.028 (Ref) 0.0011 (Ref)
d Major Diameter 8.84 - 8.972 0.348 - 0.3532
d2 Pitch Diameter 8.085 - 8.16 0.3183 - 0.3213
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.285 0.0061 - 0.0112
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

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M9 4h (External)

* Permisable values for thread Class 4h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 8.868 - 9 0.3491 - 0.3543
d2 Pitch Diameter 8.113 - 8.188 0.3194 - 0.3224
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.285 0.0061 - 0.0112
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

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M9 6e (External)

* Permisable values for thread Class 6e

# Description Value (mm) Value (Inch)
es Allowance 0.063 (Ref) 0.0025 (Ref)
d Major Diameter 8.725 - 8.937 0.3435 - 0.3519
d2 Pitch Diameter 8.007 - 8.125 0.3152 - 0.3199
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.316 0.0061 - 0.0124
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

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M9 6g (External)

* Permisable values for thread Class 6g

# Description Value (mm) Value (Inch)
es Allowance 0.028 (Ref) 0.0011 (Ref)
d Major Diameter 8.76 - 8.972 0.3449 - 0.3532
d2 Pitch Diameter 8.042 - 8.16 0.3166 - 0.3213
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.316 0.0061 - 0.0124
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

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M9 6h (External)

* Permisable values for thread Class 6h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 8.788 - 9 0.346 - 0.3543
d2 Pitch Diameter 8.07 - 8.188 0.3177 - 0.3224
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.316 0.0061 - 0.0124
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

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M9 8e (External)

* Permisable values for thread Class 8e

# Description Value (mm) Value (Inch)
es Allowance 0.063 (Ref) 0.0025 (Ref)
d Major Diameter 8.602 - 8.937 0.3387 - 0.3519
d2 Pitch Diameter 7.935 - 8.125 0.3124 - 0.3199
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.361 0.0061 - 0.0142
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

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M9 8g (External)

* Permisable values for thread Class 8g

# Description Value (mm) Value (Inch)
es Allowance 0.028 (Ref) 0.0011 (Ref)
d Major Diameter 8.637 - 8.972 0.34 - 0.3532
d2 Pitch Diameter 7.97 - 8.16 0.3138 - 0.3213
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.361 0.0061 - 0.0142
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

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M9 5g4g (External)

* Permisable values for thread Class 5g4g

# Description Value (mm) Value (Inch)
es Allowance 0.028 (Ref) 0.0011 (Ref)
d Major Diameter 8.84 - 8.972 0.348 - 0.3532
d2 Pitch Diameter 8.065 - 8.16 0.3175 - 0.3213
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.3 0.0061 - 0.0118
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 5h4h (External)

* Permisable values for thread Class 5h4h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 8.868 - 9 0.3491 - 0.3543
d2 Pitch Diameter 8.093 - 8.188 0.3186 - 0.3224
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.3 0.0061 - 0.0118
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 5g6g (External)

* Permisable values for thread Class 5g6g

# Description Value (mm) Value (Inch)
es Allowance 0.028 (Ref) 0.0011 (Ref)
d Major Diameter 8.76 - 8.972 0.3449 - 0.3532
d2 Pitch Diameter 8.065 - 8.16 0.3175 - 0.3213
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.3 0.0061 - 0.0118
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 7g6g (External)

* Permisable values for thread Class 7g6g

# Description Value (mm) Value (Inch)
es Allowance 0.028 (Ref) 0.0011 (Ref)
d Major Diameter 8.76 - 8.972 0.3449 - 0.3532
d2 Pitch Diameter 8.01 - 8.16 0.3154 - 0.3213
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.337 0.0061 - 0.0133
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 7h6h (External)

* Permisable values for thread Class 7h6h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 8.788 - 9 0.346 - 0.3543
d2 Pitch Diameter 8.038 - 8.188 0.3165 - 0.3224
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.337 0.0061 - 0.0133
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 7e6e (External)

* Permisable values for thread Class 7e6e

# Description Value (mm) Value (Inch)
es Allowance 0.063 (Ref) 0.0025 (Ref)
d Major Diameter 8.725 - 8.937 0.3435 - 0.3519
d2 Pitch Diameter 7.975 - 8.125 0.314 - 0.3199
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.337 0.0061 - 0.0133
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 9e8e (External)

* Permisable values for thread Class 9e8e

# Description Value (mm) Value (Inch)
es Allowance 0.063 (Ref) 0.0025 (Ref)
d Major Diameter 8.602 - 8.937 0.3387 - 0.3519
d2 Pitch Diameter 7.889 - 8.125 0.3106 - 0.3199
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.387 0.0061 - 0.0152
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 9g8g (External)

* Permisable values for thread Class 9g8g

# Description Value (mm) Value (Inch)
es Allowance 0.028 (Ref) 0.0011 (Ref)
d Major Diameter 8.637 - 8.972 0.34 - 0.3532
d2 Pitch Diameter 7.924 - 8.16 0.312 - 0.3213
R Root Radius 0.156 (Min) 0.0061 (Min)
C Root Truncation 0.156 - 0.387 0.0061 - 0.0152
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 4H (Internal)

* Permisable values for thread Class 4H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 7.647 - 7.817 0.3011 - 0.3078
D2 Pitch Diameter 8.188 - 8.288 0.3224 - 0.3263
D Major Diameter 9 (Min) 0.3543 (Min)
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

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M9 5H (Internal)

* Permisable values for thread Class 5H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 7.647 - 7.859 0.3011 - 0.3094
D2 Pitch Diameter 8.188 - 8.313 0.3224 - 0.3273
D Major Diameter 9 (Min) 0.3543 (Min)
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 5G (Internal)

* Permisable values for thread Class 5G

# Description Value (mm) Value (Inch)
EL Allowance 0.028 (Ref) 0.0011 (Ref)
D1 Minor Diameter 7.675 - 7.887 0.3022 - 0.3105
D2 Pitch Diameter 8.216 - 8.341 0.3235 - 0.3284
D Major Diameter 9 (Min) 0.3543 (Min)
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 6H (Internal)

* Permisable values for thread Class 6H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 7.647 - 7.912 0.3011 - 0.3115
D2 Pitch Diameter 8.188 - 8.348 0.3224 - 0.3287
D Major Diameter 9 (Min) 0.3543 (Min)
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 6G (Internal)

* Permisable values for thread Class 6G

# Description Value (mm) Value (Inch)
EL Allowance 0.028 (Ref) 0.0011 (Ref)
D1 Minor Diameter 7.675 - 7.94 0.3022 - 0.3126
D2 Pitch Diameter 8.216 - 8.376 0.3235 - 0.3298
D Major Diameter 9 (Min) 0.3543 (Min)
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 7H (Internal)

* Permisable values for thread Class 7H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 7.647 - 7.982 0.3011 - 0.3143
D2 Pitch Diameter 8.188 - 8.388 0.3224 - 0.3302
D Major Diameter 9 (Min) 0.3543 (Min)
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 7G (Internal)

* Permisable values for thread Class 7G

# Description Value (mm) Value (Inch)
EL Allowance 0.028 (Ref) 0.0011 (Ref)
D1 Minor Diameter 7.675 - 8.01 0.3022 - 0.3154
D2 Pitch Diameter 8.216 - 8.416 0.3235 - 0.3313
D Major Diameter 9 (Min) 0.3543 (Min)
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

M9 8G (Internal)

* Permisable values for thread Class 8G

# Description Value (mm) Value (Inch)
EL Allowance 0.028 (Ref) 0.0011 (Ref)
D1 Minor Diameter 7.675 - 8.1 0.3022 - 0.3189
D2 Pitch Diameter 8.216 - 8.466 0.3235 - 0.3333
D Major Diameter 9 (Min) 0.3543 (Min)
LE Normal Length of Engagement 4 - 12 0.1575 - 0.4724

* Back to Thread Class Selection

Tap Drill Sizes for M9

  • If not specified, assume a thread depth of 75%.
  • You can learn more about thread depth in tapping here.
  • To get the tap drill size in other depths, use our Tap Drill Size Calculator .
Thread Depth Tap Drill Size (Inch) Tap Drill Size (mm)
55% 0.319 8.11
60% 0.316 8.03
65% 0.313 7.94
70% 0.310 7.86
75% 0.306 7.78
80% 0.303 7.70
85% 0.300 7.62

Over Wire Measurements for M9


* OverWire is a measuring method to obatin the pitch diameter of threads. It is mostly used when a manufacturer does not have a Go/Nogo gauge for a thread. You can learn more about it here

mm Inch
Permissible Wire Diameter Range 0.631 - 1.263 0.0249 - 0.0497
Ideal Wire Diameter 0.722 0.0284
Possible Wires
From Standard Sets		 * 0.722
* 0.866
* 1.01
* 1.155
 * 0.0262
* 0.0289

Once you knoe your wire diameter, you need to find out what is the premissable Measurement for your pitch diameter (Depending on the class). Use our Over Wire Calculator to find out!


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