Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

UNC and UNF - Unified Inch Screw Threads

ANSI/ASME B1.1 Unified National Thread - UNC Coarse series and UNF Fine series

Sponsored Links

  • UNC – Unified National Coarse Thread - comparable with the ISO metric thread
  • UNF – Unified National Fine Thread

  • Female and Male UNC/UNF threads are both parallel
  • The UNC/UNF flank angle is 60°

Unified threads comes in three different classes:

  1. for applications where a liberal tolerance is required to permit easy assembly even with slightly nicked threads
  2. most commonly used class for general applications
  3. for applications where closeness of fit and/or accuracy of thread elements are important

UNC - Unified Coarse Threads

UNC threads according ANSI B1.1:

Major Diameter
(in)
Threads per inchMajor Diameter
(in)
Major Diameter
(mm)
Tap Drill Size
(mm)
Pitch
(mm)
#1 - 64 64 0.073 1.854 1.50 0.397
#2 - 56 56 0.086 2.184 1.80 0.453
#3 - 48 48 0.099 2.515 2.10 0.529
#4 - 40 40 0.112 2.845 2.35 0.635
#5 - 40 40 0.125 3.175 2.65 0.635
#6 - 32 32 0.138 3.505 2.85 0.794
#8 - 32 32 0.164 4.166 3.50 0.794
#10 - 24 24 0.190 4.826 4.00 1.058
#12 - 24 24 0.216 5.486 4.65 1.058
1/4" - 20 20 0.250 6.350 5.35 1.270
5/16" - 18 18 0.313 7.938 6.80 1.411
3/8" - 16 16 0.375 9.525 8.25 1.587
7/16" - 14 14 0.438 11.112 9.65 1.814
1/2" - 13 13 0.500 12.700 11.15 1.954
9/16" - 12 12 0.563 14.288 12.60 2.117
5/8" - 11 11 0.625 15.875 14.05 2.309
3/4" - 10 10 0.750 19.050 17.00 2.540
7/8" - 9 9 0.875 22.225 20.00 2.822
1" - 8 8 1.000 25.400 22.85 3.175
1 1/8" - 7 7 1.125 28.575 25.65 3.628
1 1/4" - 7 7 1.250 31.750 28.85 3.628
1 3/8" - 6 6 1.375 43.925 31.55 4.233
1 1/2" - 6 6 1.500 38.100 34.70 4.233
1 3/4" - 5 5 1.750 44.450 40.40 5.080
2" - 4 1/2 4 1/2 2.000 50.800 46.30 5.644
2 1/4" - 4 1/2 4 1/2 2.250 57.150 52.65 5.644
2 1/2" - 4 4 2.500 63.500 58.50 6.350
2 3/4" - 4 4 2.750 69.850 64.75 6.350
3" - 4 4 3.000 76.200 71.10 6.350
3 1/4" - 4 4 3.250 82.550 77.45 6.350
3 1/2" - 4 4 3.500 88.900 83.80 6.350
3 3/4" - 4 4 3.750 95.250 90.15 6.350
4" - 4 4 4.000 101.600 96.50 6.350

Example - Typical designation of an UNC thread

  • 1/4” x 20 UNC

UNF - Unified National Fine Threads

UNF threads ANSI B1.1:

Major Diameter
(in)
Threads per inchMajor Diameter 
(in)
Major Diameter
(mm)
Tap Drill Size
(mm)
Pitch
(mm)
#0 - 80 80 0.060 1.524 1.25 0.317
#1 - 72 72 0.073 1.854 1.55 0.353
#2 - 64 64 0.086 2.184 1.90 0.397
#3 - 56 56 0.099 2.515 2.15 0.453
#4 - 48 48 0.112 2.845 2.40 0.529
#5 - 44 44 0.125 3.175 2.70 0.577
#6 - 40 40 0.138 3.505 2.95 0.635
#8 - 36 36 0.164 4.166 3.50 0.705
#10 - 32 32 0.190 4.826 4.10 0.794
#12 - 28 28 0.216 5.486 4.70 0.907
1/4" - 28 28 0.250 6.350 5.50 0.907
5/16" - 24 24 0.313 7.938 6.90 1.058
3/8" - 24 24 0.375 9.525 8.50 1.058
7/16" - 20 20 0.438 11.112 9.90 1.270
1/2" - 20 20 0.500 12.700 11.50 1.270
9/16" - 18 18 0.563 14.288 12.90 1.411
5/8" - 18 18 0.625 15.875 14.50 1.411
3/4" - 16 16 0.750 19.050 17.50 1.587
7/8" - 14 14 0.875 22.225 20.40 1.814
1" - 12 12 1.000 25.400 23.25 2.117
1 1/8" - 12 12 1.125 28.575 26.50 2.117
1 1/4" - 12 12 1.250 31.750 29.50 2.117
1 3/8" - 12 12 1.375 34.925 32.75 2.117
1 1/2" - 12 12 1.500 38.100 36.00 2.117

Example - Typical designation of an UNF thread

  • 1/2” x 20 UNF
Sponsored Links

Related Topics

Related Documents

Sponsored Links

Share

Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Privacy

We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.

Topics

Unit Converters

Temperature

oC
oF


Load Calculator!

Length

m
km
in
ft
yards
miles
naut miles


Load Calculator!

Area

m2
km2
in2
ft2
miles2
acres


Load Calculator!

Volume

m3
liters
in3
ft3
us gal


Load Calculator!

Weight

kgf
N
lbf


Load Calculator!

Velocity

m/s
km/h
ft/min
ft/s
mph
knots


Load Calculator!

Pressure

Pa (N/m2)
bar
mm H2O
kg/cm2
psi
inches H2O


Load Calculator!

Flow

m3/s
m3/h
US gpm
cfm


Load Calculator!

6 17

This website use cookies. By continuing to browse you are agreeing to our use of cookies! Learn more