M8 X 1 - Basic Thread Dimensions

Property mm Inch
Nominal Diameter 8 0.315
Pitch (Distance) 1 0.0394
Pitch Diameter 7.35 0.2894
Minor Diameter 6.917 0.2723
Thread Height 0.541 0.0213
Addendum 0.325 0.0128
Crest (External)
Root (Internal)
0.125 0.0049
Tap Drill Size
(75% depth)
7.03 0.277
Lead Angle
(Single Start)
2.48°
Thread Family Metric Fine Pitch (MF)
Relevant Standards ISO 68-1, ISO 9651-1, ISO 965-2, ISO 261,DIN 13
Equivalent Inch Thread5/16 - 24 UNF

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

Table of Content


M8 X 1 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

M8 X 1 4g (External)

* Permisable values for thread Class 4g

# Description Value (mm) Value (Inch)
es Allowance 0.026 (Ref) 0.001 (Ref)
d Major Diameter 7.862 - 7.974 0.3095 - 0.3139
d2 Pitch Diameter 7.253 - 7.324 0.2856 - 0.2883
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.236 0.0049 - 0.0093
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

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M8 X 1 4h (External)

* Permisable values for thread Class 4h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 7.888 - 8 0.3106 - 0.315
d2 Pitch Diameter 7.279 - 7.35 0.2866 - 0.2894
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.236 0.0049 - 0.0093
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

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M8 X 1 6e (External)

* Permisable values for thread Class 6e

# Description Value (mm) Value (Inch)
es Allowance 0.06 (Ref) 0.0024 (Ref)
d Major Diameter 7.76 - 7.94 0.3055 - 0.3126
d2 Pitch Diameter 7.178 - 7.29 0.2826 - 0.287
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.264 0.0049 - 0.0104
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

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M8 X 1 6g (External)

* Permisable values for thread Class 6g

# Description Value (mm) Value (Inch)
es Allowance 0.026 (Ref) 0.001 (Ref)
d Major Diameter 7.794 - 7.974 0.3069 - 0.3139
d2 Pitch Diameter 7.212 - 7.324 0.2839 - 0.2883
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.264 0.0049 - 0.0104
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

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M8 X 1 6h (External)

* Permisable values for thread Class 6h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 7.82 - 8 0.3079 - 0.315
d2 Pitch Diameter 7.238 - 7.35 0.285 - 0.2894
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.264 0.0049 - 0.0104
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 8e (External)

* Permisable values for thread Class 8e

# Description Value (mm) Value (Inch)
es Allowance 0.06 (Ref) 0.0024 (Ref)
d Major Diameter 7.66 - 7.94 0.3016 - 0.3126
d2 Pitch Diameter 7.11 - 7.29 0.2799 - 0.287
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.305 0.0049 - 0.012
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

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M8 X 1 8g (External)

* Permisable values for thread Class 8g

# Description Value (mm) Value (Inch)
es Allowance 0.026 (Ref) 0.001 (Ref)
d Major Diameter 7.694 - 7.974 0.3029 - 0.3139
d2 Pitch Diameter 7.144 - 7.324 0.2813 - 0.2883
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.305 0.0049 - 0.012
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 5g4g (External)

* Permisable values for thread Class 5g4g

# Description Value (mm) Value (Inch)
es Allowance 0.026 (Ref) 0.001 (Ref)
d Major Diameter 7.862 - 7.974 0.3095 - 0.3139
d2 Pitch Diameter 7.234 - 7.324 0.2848 - 0.2883
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.25 0.0049 - 0.0098
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 5h4h (External)

* Permisable values for thread Class 5h4h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 7.888 - 8 0.3106 - 0.315
d2 Pitch Diameter 7.26 - 7.35 0.2858 - 0.2894
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.25 0.0049 - 0.0098
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 5g6g (External)

* Permisable values for thread Class 5g6g

# Description Value (mm) Value (Inch)
es Allowance 0.026 (Ref) 0.001 (Ref)
d Major Diameter 7.794 - 7.974 0.3069 - 0.3139
d2 Pitch Diameter 7.234 - 7.324 0.2848 - 0.2883
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.25 0.0049 - 0.0098
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 7g6g (External)

* Permisable values for thread Class 7g6g

# Description Value (mm) Value (Inch)
es Allowance 0.026 (Ref) 0.001 (Ref)
d Major Diameter 7.794 - 7.974 0.3069 - 0.3139
d2 Pitch Diameter 7.184 - 7.324 0.2828 - 0.2883
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.282 0.0049 - 0.0111
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 7h6h (External)

* Permisable values for thread Class 7h6h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 7.82 - 8 0.3079 - 0.315
d2 Pitch Diameter 7.21 - 7.35 0.2839 - 0.2894
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.282 0.0049 - 0.0111
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 7e6e (External)

* Permisable values for thread Class 7e6e

# Description Value (mm) Value (Inch)
es Allowance 0.06 (Ref) 0.0024 (Ref)
d Major Diameter 7.76 - 7.94 0.3055 - 0.3126
d2 Pitch Diameter 7.15 - 7.29 0.2815 - 0.287
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.282 0.0049 - 0.0111
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 9e8e (External)

* Permisable values for thread Class 9e8e

# Description Value (mm) Value (Inch)
es Allowance 0.06 (Ref) 0.0024 (Ref)
d Major Diameter 7.66 - 7.94 0.3016 - 0.3126
d2 Pitch Diameter 7.066 - 7.29 0.2782 - 0.287
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.328 0.0049 - 0.0129
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 9g8g (External)

* Permisable values for thread Class 9g8g

# Description Value (mm) Value (Inch)
es Allowance 0.026 (Ref) 0.001 (Ref)
d Major Diameter 7.694 - 7.974 0.3029 - 0.3139
d2 Pitch Diameter 7.1 - 7.324 0.2795 - 0.2883
R Root Radius 0.125 (Min) 0.0049 (Min)
C Root Truncation 0.125 - 0.328 0.0049 - 0.0129
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 4H (Internal)

* Permisable values for thread Class 4H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 6.917 - 7.067 0.2723 - 0.2782
D2 Pitch Diameter 7.35 - 7.445 0.2894 - 0.2931
D Major Diameter 8 (Min) 0.315 (Min)
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 5H (Internal)

* Permisable values for thread Class 5H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 6.917 - 7.107 0.2723 - 0.2798
D2 Pitch Diameter 7.35 - 7.468 0.2894 - 0.294
D Major Diameter 8 (Min) 0.315 (Min)
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 5G (Internal)

* Permisable values for thread Class 5G

# Description Value (mm) Value (Inch)
EL Allowance 0.026 (Ref) 0.001 (Ref)
D1 Minor Diameter 6.943 - 7.133 0.2733 - 0.2808
D2 Pitch Diameter 7.376 - 7.494 0.2904 - 0.295
D Major Diameter 8 (Min) 0.315 (Min)
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 6H (Internal)

* Permisable values for thread Class 6H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 6.917 - 7.153 0.2723 - 0.2816
D2 Pitch Diameter 7.35 - 7.5 0.2894 - 0.2953
D Major Diameter 8 (Min) 0.315 (Min)
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 6G (Internal)

* Permisable values for thread Class 6G

# Description Value (mm) Value (Inch)
EL Allowance 0.026 (Ref) 0.001 (Ref)
D1 Minor Diameter 6.943 - 7.179 0.2733 - 0.2826
D2 Pitch Diameter 7.376 - 7.526 0.2904 - 0.2963
D Major Diameter 8 (Min) 0.315 (Min)
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 7H (Internal)

* Permisable values for thread Class 7H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 6.917 - 7.217 0.2723 - 0.2841
D2 Pitch Diameter 7.35 - 7.54 0.2894 - 0.2969
D Major Diameter 8 (Min) 0.315 (Min)
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 7G (Internal)

* Permisable values for thread Class 7G

# Description Value (mm) Value (Inch)
EL Allowance 0.026 (Ref) 0.001 (Ref)
D1 Minor Diameter 6.943 - 7.243 0.2733 - 0.2852
D2 Pitch Diameter 7.376 - 7.566 0.2904 - 0.2979
D Major Diameter 8 (Min) 0.315 (Min)
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


M8 X 1 8G (Internal)

* Permisable values for thread Class 8G

# Description Value (mm) Value (Inch)
EL Allowance 0.026 (Ref) 0.001 (Ref)
D1 Minor Diameter 6.943 - 7.318 0.2733 - 0.2881
D2 Pitch Diameter 7.376 - 7.612 0.2904 - 0.2997
D Major Diameter 8 (Min) 0.315 (Min)
LE Normal Length of Engagement 3 - 9 0.1181 - 0.3543

* Back to Thread Class Selection


Tap Drill Sizes for M8 X 1

  • 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% 0.287 7.29
60% 0.284 7.22
65% 0.282 7.16
70% 0.279 7.09
75% 0.277 7.03
80% 0.274 6.96
85% 0.271 6.90

Over Wire Measurements for M8 X 1


* 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 0.505 - 1.01 0.0199 - 0.0398
Ideal Wire Diameter 0.577 0.0227
Possible Wires
From Standard Sets
* 0.52
* 0.577
* 0.722
* 0.866
* 0.0206
* 0.0214
* 0.0222
* 0.0241
* 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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