7/8 - 16 16-UN - Basic Thread Dimensions

Property Inch mm
Nominal Diameter 0.875 22.225
Pitch (TPI)16
Pitch (Distance) 0.0625 1.588
Pitch Diameter 0.8344 21.194
Minor Diameter 0.8006 20.335
Thread Height 0.0338 0.859
Addendum 0.0203 0.516
Crest (External)
Root (Internal)
0.0078 0.198
Tap Drill Size
(75% depth)
0.814 20.68
Lead Angle
(Single Start)
1.37°
Thread Family Unified Constant Pitch 16 TPI (16-UN)
Relevant Standards ASME B1.1-2003
Equivalent Metric ThreadM22 X 1.5

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

Table of Content


7/8 - 16 16-UN Possible Thread Classes

External Threads

Choose tolerance class: 2A, 3A

Metric ISO External Thread - Tolerance sketch

Internal Threads

Choose tolerance class: 2B, 3B

Metric ISO Internal Thread - Tolerance sketch

7/8 - 16 16-UN 2A (External)

* Permisable values for thread Class 2A

# Description Value (Inch) Value (mm)
es Allowance 0.0014 (Ref) 0.036 (Ref)
d Major Diameter 0.8642 - 0.8736 21.951 - 22.189
d2 Pitch Diameter 0.8284 - 0.833 21.041 - 21.158
d3 Minor Diameter
(UNR Only)
0.7992 (Ref) 20.3 (Ref)
α Varation of 30° anngle (+/-)
P Varation of pitch (+/-) 0.0013 (Ref) 0.033 (Ref)

* Values are calculated for Length of engagement of 5xPitch. For calculations of different engagement length use the Thread Calculator

* Back to Thread Class Selection


7/8 - 16 16-UN 3A (External)

* Permisable values for thread Class 3A

# Description Value (Inch) Value (mm)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 0.8656 - 0.875 21.986 - 22.225
d2 Pitch Diameter 0.8309 - 0.8344 21.105 - 21.194
d3 Minor Diameter
(UNR Only)
0.8006 (Ref) 20.335 (Ref)
α Varation of 30° anngle (+/-)
P Varation of pitch (+/-) 0.001 (Ref) 0.025 (Ref)

* Values are calculated for Length of engagement of 5xPitch. For calculations of different engagement length use the Thread Calculator

* Back to Thread Class Selection


7/8 - 16 16-UN 2B (Internal)

* Permisable values for thread Class 2B

# Description Value (Inch) Value (mm)
D1 Minor Diameter 0.807 - 0.821 20.498 - 20.853
D2 Pitch Diameter 0.8344 - 0.8404 21.194 - 21.346
D Major Diameter 0.8750 (Min) 22.225 (Min)
α Varation of 30° anngle (+/-)
P Varation of Pitch (+/-) 0.0017 (Ref) 0.043 (Ref)

* Values are calculated for Length of engagement of 5xPitch. For calculations of different engagement length use the Thread Calculator

* Back to Thread Class Selection


7/8 - 16 16-UN 3B (Internal)

* Permisable values for thread Class 3B

# Description Value (Inch) Value (mm)
D1 Minor Diameter 0.8073 - 0.8158 20.505 - 20.721
D2 Pitch Diameter 0.8344 - 0.8389 21.194 - 21.308
D Major Diameter 0.8750 (Min) 22.225 (Min)
α Varation of 30° anngle (+/-)
P Varation of Pitch (+/-) 0.0013 (Ref) 0.033 (Ref)

* Values are calculated for Length of engagement of 5xPitch. For calculations of different engagement length use the Thread Calculator

* Back to Thread Class Selection


Tap Drill Sizes for 7/8 - 16 16-UN

  • 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% 0.830 21.09
60% 0.826 20.99
65% 0.822 20.88
70% 0.818 20.78
75% 0.814 20.68
80% 0.810 20.57
85% 0.806 20.47

Over Wire Measurements for 7/8 - 16 16-UN


* 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

Inch mm
Permissible Wire Diameter Range 0.0316 - 0.0631 0.802 - 1.604
Ideal Wire Diameter 0.0361 0.917
Possible Wires
From Standard Sets
* 0.866
* 1.01
* 1.155
* 1.443

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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