M1 - Basic Thread Dimensions

Property mm Inch
Nominal Diameter 1 0.0394
Pitch (Distance) 0.25 0.0098
Pitch Diameter 0.838 0.033
Minor Diameter 0.729 0.0287
Thread Height 0.135 0.0053
Addendum 0.081 0.0032
Crest (External)
Root (Internal)		 0.031 0.0012
Tap Drill Size
(75% depth)		 0.76 0.03
Lead Angle
(Single Start)		 5.42°
Thread Family Metric Coarse Pitch (MC)
Relevant Standards ISO 68-1, ISO 9651-1, ISO 965-2, ISO 261,DIN 13
Equivalent Inch Thread#0 - 80 UNF

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

Table of Content

M1 Possible Thread Classes

External Threads

Choose tolerance class: 4g, 4h, 6g, 6h, 5g4g, 5h4h, 5g6g

Metric ISO External Thread - Tolerance sketch

Internal Threads

Choose tolerance class: 4H, 5H, 5G

Metric ISO Internal Thread - Tolerance sketch

M1 4g (External)

* Permisable values for thread Class 4g

# Description Value (mm) Value (Inch)
es Allowance 0.018 (Ref) 0.0007 (Ref)
d Major Diameter 0.94 - 0.982 0.037 - 0.0387
d2 Pitch Diameter 0.786 - 0.82 0.0309 - 0.0323
R Root Radius 0.031 (Min) 0.0012 (Min)
C Root Truncation 0.031 - 0.07 0.0012 - 0.0028
LE Normal Length of Engagement 0.6 - 1.7 0.0236 - 0.0669

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M1 4h (External)

* Permisable values for thread Class 4h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 0.958 - 1 0.0377 - 0.0394
d2 Pitch Diameter 0.804 - 0.838 0.0317 - 0.033
R Root Radius 0.031 (Min) 0.0012 (Min)
C Root Truncation 0.031 - 0.07 0.0012 - 0.0028
LE Normal Length of Engagement 0.6 - 1.7 0.0236 - 0.0669

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M1 6g (External)

* Permisable values for thread Class 6g

# Description Value (mm) Value (Inch)
es Allowance 0.018 (Ref) 0.0007 (Ref)
d Major Diameter 0.915 - 0.982 0.036 - 0.0387
d2 Pitch Diameter 0.767 - 0.82 0.0302 - 0.0323
R Root Radius 0.031 (Min) 0.0012 (Min)
C Root Truncation 0.031 - 0.08 0.0012 - 0.0031
LE Normal Length of Engagement 0.6 - 1.7 0.0236 - 0.0669

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M1 6h (External)

* Permisable values for thread Class 6h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 0.933 - 1 0.0367 - 0.0394
d2 Pitch Diameter 0.785 - 0.838 0.0309 - 0.033
R Root Radius 0.031 (Min) 0.0012 (Min)
C Root Truncation 0.031 - 0.08 0.0012 - 0.0031
LE Normal Length of Engagement 0.6 - 1.7 0.0236 - 0.0669

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M1 5g4g (External)

* Permisable values for thread Class 5g4g

# Description Value (mm) Value (Inch)
es Allowance 0.018 (Ref) 0.0007 (Ref)
d Major Diameter 0.94 - 0.982 0.037 - 0.0387
d2 Pitch Diameter 0.778 - 0.82 0.0306 - 0.0323
R Root Radius 0.031 (Min) 0.0012 (Min)
C Root Truncation 0.031 - 0.074 0.0012 - 0.0029
LE Normal Length of Engagement 0.6 - 1.7 0.0236 - 0.0669

* Back to Thread Class Selection

M1 5h4h (External)

* Permisable values for thread Class 5h4h

# Description Value (mm) Value (Inch)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 0.958 - 1 0.0377 - 0.0394
d2 Pitch Diameter 0.796 - 0.838 0.0313 - 0.033
R Root Radius 0.031 (Min) 0.0012 (Min)
C Root Truncation 0.031 - 0.074 0.0012 - 0.0029
LE Normal Length of Engagement 0.6 - 1.7 0.0236 - 0.0669

* Back to Thread Class Selection

M1 5g6g (External)

* Permisable values for thread Class 5g6g

# Description Value (mm) Value (Inch)
es Allowance 0.018 (Ref) 0.0007 (Ref)
d Major Diameter 0.915 - 0.982 0.036 - 0.0387
d2 Pitch Diameter 0.778 - 0.82 0.0306 - 0.0323
R Root Radius 0.031 (Min) 0.0012 (Min)
C Root Truncation 0.031 - 0.074 0.0012 - 0.0029
LE Normal Length of Engagement 0.6 - 1.7 0.0236 - 0.0669

* Back to Thread Class Selection

M1 4H (Internal)

* Permisable values for thread Class 4H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 0.729 - 0.774 0.0287 - 0.0305
D2 Pitch Diameter 0.838 - 0.883 0.033 - 0.0348
D Major Diameter 1 (Min) 0.0394 (Min)
LE Normal Length of Engagement 0.6 - 1.7 0.0236 - 0.0669

* Back to Thread Class Selection

M1 5H (Internal)

* Permisable values for thread Class 5H

# Description Value (mm) Value (Inch)
EL Allowance 0 (Ref) 0 (Ref)
D1 Minor Diameter 0.729 - 0.785 0.0287 - 0.0309
D2 Pitch Diameter 0.838 - 0.894 0.033 - 0.0352
D Major Diameter 1 (Min) 0.0394 (Min)
LE Normal Length of Engagement 0.6 - 1.7 0.0236 - 0.0669

* Back to Thread Class Selection

M1 5G (Internal)

* Permisable values for thread Class 5G

# Description Value (mm) Value (Inch)
EL Allowance 0.018 (Ref) 0.0007 (Ref)
D1 Minor Diameter 0.747 - 0.803 0.0294 - 0.0316
D2 Pitch Diameter 0.856 - 0.912 0.0337 - 0.0359
D Major Diameter 1 (Min) 0.0394 (Min)
LE Normal Length of Engagement 0.6 - 1.7 0.0236 - 0.0669

* Back to Thread Class Selection

Tap Drill Sizes for M1

  • 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% 0.032 0.82
60% 0.032 0.81
65% 0.031 0.79
70% 0.030 0.77
75% 0.030 0.76
80% 0.029 0.74
85% 0.029 0.72

Over Wire Measurements for M1


* 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 0.126 - 0.253 0.005 - 0.0099
Ideal Wire Diameter 0.144 0.0057
Possible Wires
From Standard Sets		 * 0.13
* 0.144
* 0.173
* 0.202
* 0.231
 * 0.006
* 0.0064
* 0.0072
* 0.008
* 0.009

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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