15/16 - 28 28-UN - Basic Thread Dimensions

Property Inch mm
Nominal Diameter 0.937 23.8
Pitch (TPI)28
Pitch (Distance) 0.0357 0.907
Pitch Diameter 0.9138 23.211
Minor Diameter 0.8945 22.72
Thread Height 0.0193 0.49
Addendum 0.0116 0.295
Crest (External)
Root (Internal)
0.0045 0.114
Tap Drill Size
(75% depth)
0.902 22.92
Lead Angle
(Single Start)
0.71°
Thread Family Unified Constant Pitch 28 TPI (28-UN)
Relevant Standards ASME B1.1-2003
Equivalent Metric ThreadM24 X 1

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

Table of Content


15/16 - 28 28-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

15/16 - 28 28-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 0.9294 - 0.9359 23.607 - 23.772
d2 Pitch Diameter 0.909 - 0.9127 23.089 - 23.183
d3 Minor Diameter
(UNR Only)
0.8934 (Ref) 22.692 (Ref)
α Varation of 30° anngle (+/-) 1.3333°
P Varation of pitch (+/-) 0.0011 (Ref) 0.028 (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


15/16 - 28 28-UN 3A (External)

* Permisable values for thread Class 3A

# Description Value (Inch) Value (mm)
es Allowance 0 (Ref) 0 (Ref)
d Major Diameter 0.9305 - 0.937 23.635 - 23.8
d2 Pitch Diameter 0.911 - 0.9138 23.139 - 23.211
d3 Minor Diameter
(UNR Only)
0.8945 (Ref) 22.72 (Ref)
α Varation of 30° anngle (+/-) 1.3333°
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


15/16 - 28 28-UN 2B (Internal)

* Permisable values for thread Class 2B

# Description Value (Inch) Value (mm)
D1 Minor Diameter 0.898 - 0.907 22.809 - 23.038
D2 Pitch Diameter 0.9138 - 0.9186 23.211 - 23.332
D Major Diameter 0.9370 (Min) 23.8 (Min)
α Varation of 30° anngle (+/-) 1.3333°
P Varation of Pitch (+/-) 0.0014 (Ref) 0.036 (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


15/16 - 28 28-UN 3B (Internal)

* Permisable values for thread Class 3B

# Description Value (Inch) Value (mm)
D1 Minor Diameter 0.8983 - 0.9046 22.817 - 22.977
D2 Pitch Diameter 0.9138 - 0.9174 23.211 - 23.302
D Major Diameter 0.9370 (Min) 23.8 (Min)
α Varation of 30° anngle (+/-) 1.3333°
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 15/16 - 28 28-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% 0.911 23.15
60% 0.909 23.09
65% 0.907 23.03
70% 0.905 22.97
75% 0.902 22.92
80% 0.900 22.86
85% 0.898 22.80

Over Wire Measurements for 15/16 - 28 28-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 0.018 - 0.0361 0.458 - 0.916
Ideal Wire Diameter 0.0206 0.524
Possible Wires
From Standard Sets
* 0.018
* 0.0193
* 0.0206
* 0.0214
* 0.0222
* 0.0241
* 0.0262
* 0.0289
* 0.462
* 0.52
* 0.577
* 0.722
* 0.866

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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