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UNC Thread Chart and UNF Thread Chart

UNC Thread and UNF Thread


Table Of Content


What is UNC Thread?

What is UNC Thread?

UNC thread also called unified national coarse. UNC (Coarse) thread per inch (1/4"-20). Unified national thread good for general assembly. UNC threads most typical designation for industrial applications bolts and nuts.

UNC Thread Chart

Major Diameter (in) Pitch (mm) Major Diameter Threads per inch Tap Drill Size (mm)
(mm)
4" - 4 6.350 101.600 4tpi 96.50
3 3/4" - 4 6.350 95.250 4tpi 90.15
3 1/4" - 4 6.350 82.550 4tpi 77.45
2 3/4" - 4 6.350 69.850 4tpi 64.75
2 1/2" - 4 6.350 63.500 4tpi 58.50
2" - 4 1/2 5.644 50.800 4 1/2tpi 46.30
1 3/4" - 5 5.080 44.450 5tpi 40.40
1 3/8" - 6 4.233 34.925 6tpi 31.55
1 1/4" - 7 3.628 31.750 7tpi 28.85
1" - 8 3.175 25.400 8tpi 22.85
3/4" - 10 2.540 19.050 10tpi 17.00
5/8" - 11 2.309 15.875 11tpi 14.05
5/8" - 11 2.309 15.875 11tpi 14.05
1/2" - 13 1.954 12.700 13tpi 11.15
3/8" - 16 1.587 9.525 16tpi 8.25
1/4" - 20 1.270 6.350 20tpi 5.35
#12 - 24 1.058 5.486 24tpi 4.65
#10 - 24 1.058 4.826 24tpi 4.00
#8 - 32 0.794 4.166 32tpi 3.50
#6 - 32 0.794 3.505 32tpi 2.85
#5 - 40 0.635 3.175 40tpi 2.65
#4 - 40 0.635 2.845 40tpi 2.35
#3 - 48 0.529 2.515 48tpi 2.10
#2 - 56 0.453 2.184 56tpi 1.80

What is UNF Thread?

What is UNF Thread?

UNF thread also called unified national fine, based screw threads. UNF (Fine) threads per inch (1/4"-28). UNF standard thread offers better vibration resistance and good tensile strength. UNF thread suitable for automotive and aerospace.

UNF Thread Chart

Major Diameter (in) Pitch (mm) Size Of Tap Drill (mm) Major Diameter Threads per inch
(mm)
1 1/2" - 12 2.117 36.00 38.100 12 tpi
1 3/8" - 12 2.117 32.75 34.925 12 tpi
1 1/8" - 12 2.117 26.50 28.575 12 tpi
1" - 12 2.117 23.25 25.400 12 tpi
3/4" - 16 1.587 17.50 19.050 16 tpi
5/8" - 18 1.411 14.50 15.875 18 tpi
1/2" - 20 1.270 11.50 12.700 20 tpi
3/8" - 24 1.058 8.50 9.525 24 tpi
1/4" - 28 0.907 5.50 6.350 28 tpi
#12 - 28 0.907 4.70 5.486 28 tpi
#10 - 32 0.794 4.10 4.826 32 tpi
#8 - 36 0.705 3.50 4.166 36 tpi
#6 - 40 0.635 2.95 3.505 40 tpi
#5 - 44 0.577 2.70 3.175 44 tpi
#4 - 48 0.529 2.40 2.845 48 tpi
#3 - 56 0.453 2.15 2.515 56 tpi
#2 - 64 0.397 1.90 2.184 64 tpi
#1 - 72 0.353 1.55 1.854 72 tpi

Find Difference Between UNC Thread and UNF Thread as per ANSI B1.1

Difference Between UNF and UNC Threads

UNF Threads UNC Threads
UNF Threads UNC Threads
Unified National Fine Thread Unified National Coarse Thread
Female and Male Threads Male and Female Threads
Fine Thread Cross Thread
Allow for Closer Adjustment Faster Disassembly and Assembly
Less Tendency to Loosen Large Thread Allowances
Suitable for Sheet Metal Suitable for Universal Applications
Smaller Helix Angle Fewer Teeth of the Same Length

Browse Design Features of UNF vs UNC Threads Conversion Chart


UNF and UNC Thread Chart

Thread Designation Internal Threads Diameter External Threads Diameter Threads per Inch UNF / UNC
2-4.5 1.759 2.000 4 1/2 UNC Thread
1 1/2-6 1.320 1.500 6 UNC Thread
1 1/4-7 1.095 1.250 7 UNC Threads
1 1/8-12 1.035 1.125 12 UNF Threads
1-14 0.910 1.000 14 UNF Threads
1-8 0.865 1.000 8 UNC Thread
7/8-14 0.798 0.875 14 UNF Thread
3/4-16 0.682 0.750 16 UNF Thread
3/4-10 0.642 0.750 10 UNC Thread
5/8-18 0.565 0.625 18 UNF Threads
5/8-11 0.527 0.625 11 UNC Thread
1/2-20 0.446 0.500 20 UNF Threads
1/2-13 0.417 0.500 13 UNC Threads
3/8-24 0.330 0.375 24 UNF Threads
3/8-24 0.330 0.375 24 UNF Threads
3/8-16 0.307 0.375 16 UNC Threads
5/16-24 0.267 0.313 24 UNF Threads
5/16-18 0.252 0.313 18 UNC Thread
5/8-18 0.565 0.625 18 UNF Threads
10-32 0.156 0.190 32 UNF Thread
10-24 0.145 0.190 24 UNC Thread
8-36 0.134 0.164 36 UNF Thread
8-32 0.130 0.164 32 UNC Thread
6-40 0.111 0.136 40  UNF Threads
6-32 0.104 0.136 32 UNC Threads
5-44 0.100 0.125 44 UNF Threads
5-40 0.098 0.125 40 UNC Threads
2-64 0.069 0.086 64 UNF Threads
1-64 0.056 0.073 64 UNC Threads
0-80 0.047 0.060 80 UNF Threads

Can I Substitute a Metric Bolt for a UNC or UNF?

No, Some bolt sizes are similar, but threads are not substitutable.

Different Classes Of Thread Fit

Class 1A (external) Class 1B (internal)
Class 2A (external) Class 2B (internal)
Class 3A (external) Class 3B (internal)

Which Type of Thread is Strongest?

UNF threads is strongest thread, They have a larger tensile stress area.

Why are Coarse Threads Better for SOFT Materials?

Because coarse threads have deeper profiles, suitable for SOFT materials (aluminum, wood, or plastic)

UNC vs UNF Threads Conversion Chart

Threads Suitable for Pitch Sizes
UNC Threads Quick Installation Fewer threads per inch (TPI) 1/4-20, 3/8-16, #4-40, #8-32, 5/16-18, #6-32
UNF Threads Aerospace More threads per inch (TPI) 3/8-24, 1/4-28, #10-32, 5/16-24
(UNC Threads /UNF Threads) Metric Pitch Threads Per Inch Closest Metric Size
3/8-16 (UNC) 1.5 mm 16 TPI M10
5/16-18 (UNC) 1.25 mm 18 TPI M8
1/4-20 (UNC) 1.0 mm 20 TPI M6
#10-24 (UNC) 0.8 mm 24 TPI M5

UNC and UNF Thread Full Form

  • UNC Thread Full Form = Unified Inch Coarse Thread
  • UNF Thread Full Form = Unified Inch Fine Thread

List of Symbols Used in UNF Thread Chart

Symbol Explanation
D1 Diameter-Internal Thread
D2 Pitch Diameter-Internal Thread
n Number of threds per Inch(TPI)
P Pitch (Distance)
hs Thread Height-External Thread
Lts Length-External Thread
Td Tolerance- d

Everything You Need to Know About Unified National Thread and Unified National Coarse Applications


When to Use UNC and UNF Threads?

UNC Threads Applications UNF Threads Applications
Construction Automotive
Wood Vibration Resistance
General Purpose Machinery
SOFT Materials Aerospace
Quick Assembly Limited Space

How to Calculate the Pitch of UNF Threads or UNC Threads?

How to Calculate the Pitch of UNF Threads or UNC Threads?