7/8 - 32 32-UN - Basic Thread Dimensions

Property Inch mm
Nominal Diameter 0.875 22.225
Pitch (TPI)32
Pitch (Distance) 0.0313 0.795
Pitch Diameter 0.8547 21.709
Minor Diameter 0.8378 21.28
Thread Height 0.0169 0.429
Addendum 0.0101 0.257
Crest (External)
Root (Internal)		 0.0039 0.099
Tap Drill Size
(75% depth)		 0.844 21.45
Lead Angle
(Single Start)		 0.67°
Thread Family Unified Constant Pitch 32 TPI (32-UN)
Relevant Standards ASME B1.1-2003
Equivalent Metric ThreadM22 X 1

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

Table of Content

7/8 - 32 32-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 - 32 32-UN 2A (External)

* Permisable values for thread Class 2A

# Description Value (Inch) Value (mm)
es Allowance 0.0011 (Ref) 0.028 (Ref)
d Major Diameter 0.8679 - 0.8739 22.045 - 22.197
d2 Pitch Diameter 0.8501 - 0.8536 21.593 - 21.681
d3 Minor Diameter
(UNR Only)		 0.8367 (Ref) 21.252 (Ref)
α Varation of 30° anngle (+/-) 1.5°
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 - 32 32-UN 3A (External)

* Permisable values for thread Class 3A

# Description Value (Inch) Value (mm)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 0.869 - 0.875 22.073 - 22.225
d2 Pitch Diameter 0.8521 - 0.8547 21.643 - 21.709
d3 Minor Diameter
(UNR Only)		 0.8378 (Ref) 21.28 (Ref)
α Varation of 30° anngle (+/-) 1.5°
P Varation of pitch (+/-) 0.0008 (Ref) 0.02 (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 - 32 32-UN 2B (Internal)

* Permisable values for thread Class 2B

# Description Value (Inch) Value (mm)
D1 Minor Diameter 0.841 - 0.849 21.361 - 21.565
D2 Pitch Diameter 0.8547 - 0.8593 21.709 - 21.826
D Major Diameter 0.8750 (Min) 22.225 (Min)
α Varation of 30° anngle (+/-) 1.5°
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 - 32 32-UN 3B (Internal)

* Permisable values for thread Class 3B

# Description Value (Inch) Value (mm)
D1 Minor Diameter 0.8412 - 0.8469 21.366 - 21.511
D2 Pitch Diameter 0.8547 - 0.8581 21.709 - 21.796
D Major Diameter 0.8750 (Min) 22.225 (Min)
α Varation of 30° anngle (+/-) 1.5°
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

Tap Drill Sizes for 7/8 - 32 32-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% 0.853 21.66
60% 0.851 21.61
65% 0.849 21.55
70% 0.847 21.50
75% 0.845 21.45
80% 0.843 21.40
85% 0.840 21.35

Over Wire Measurements for 7/8 - 32 32-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 0.0158 - 0.0316 0.402 - 0.803
Ideal Wire Diameter 0.0181 0.459
Possible Wires
From Standard Sets		 * 0.016
* 0.018
* 0.0193
* 0.0206
* 0.0214
* 0.0222
* 0.0241
* 0.0262
* 0.0289
 * 0.404
* 0.433
* 0.462
* 0.52
* 0.577
* 0.722

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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