13/16-20 UNEF Thread Quick Specifications
| Parameter | Specification | |
| Thread Standard | Unified Thread Standard (UTS) | |
| Thread Series | UNEF | |
| Nominal Size | 13/16 | |
| Thread Designation | 13/16-20 UNEF | |
| Threads Per Inch (TPI) | 20 | |
| Major Diameter | 0.8120 in | 20.625 mm |
| Pitch | 0.0500 in | 1.2700 mm |
| Pitch Diameter | 0.7795 in | 19.799 mm |
| Minor Diameter | 0.7525 in | 19.114 mm |
| Thread Height | 0.0271 in | 0.6880 mm |
| Addendum | 0.0162 in | 0.4110 mm |
| Thread Angle | 60° | |
| Common Classes | 2A / 2B | |
| Typical Use | Precision electronic assemblies | |
Introduction
The 13/16-20 UNEF thread is one of the most widely used Unified National Extra Fine (UNEF) thread sizes in high-reliability electronic equipment, particularly for thread-mount feedthrough capacitors, EMI filters, RF shielding assemblies, and other precision panel-mounted components.
This page provides a complete engineering reference for 13/16-20 UNEF thread dimensions and specifications, including thread designation, major diameter, pitch, threads per inch (TPI), minor diameter, and tolerance classes.
For engineers selecting threaded mounting solutions for electronic components such as feedthrough filters, EMI filters, RF shielding components, and precision assemblies, understanding the 13/16-20 UNEF specification helps ensure proper mechanical compatibility, reliable installation, and long-term performance.
Quick Answer: The 13/16-20 UNEF thread is one of the most widely used Unified National Extra Fine (UNEF) thread sizes in high-reliability electronic equipment, particularly for thread-mount feedthrough capacitors, EMI filters, RF shielding assemblies, and other precision panel-mounted components.
A 13/16-20 UNEF thread is a Unified National Extra Fine (UNEF) screw thread defined by the Unified Thread Standard (UTS).
The designation means:
- 13/16indicates the nominal major diameter
- 20indicates 20 threads per inch (TPI)
- UNEFindicates Unified National Extra Fine thread series
13/16-20 UNEF Thread Tolerance Classes
Thread tolerance determines how tightly two mating components fit together.
The Unified Thread Standard defines several tolerance classes.
Class 2A / 2B Threads
Class 2 is the most commonly used commercial tolerance.
External Thread: 13/16-20 UNEF-2A
Internal Thread: 13/16-20 UNEF-2B
Advantages:
- Good interchangeability
- Reliable assembly
- Suitable for mass production
- Lower manufacturing cost
Typical applications:
- EMI filter mounting
- Feedthrough capacitor installation
- Industrial electronic equipment
- General instrumentation
Most commercial fasteners use Class 2.
Class 3A / 3B Threads
Class 3 provides a tighter fit.
External Thread: 13/16-20 UNEF-3A
Internal Thread: 13/16-20 UNEF-3B
They are typically selected when requirements include:
- Higher positional accuracy
- Reduced movement between mating parts
- Precision adjustment
- Aerospace or military specifications
However, tighter tolerances also mean:
- Higher machining requirements
- More expensive inspection
- Greater sensitivity to contamination
13/16-20 UNEF vs Similar Thread Sizes
Engineers often need to determine whether another thread specification can replace 13/16-20 UNEF.
13/16-20 UNEF vs M20 × 1.5
| Parameter | 13/16-20 UNEF | M20 × 1.5 |
| Standard | Unified | Metric ISO |
| Major Diameter | 20.625 mm | 20.00 mm |
| Pitch | 1.2700 mm | 1.500 mm |
| Pitch Diameter | 19.799 mm | 19.026 mm |
| Minor Diameter | 19.114 mm | 18.376 mm |
| Thread Height | 0.6880 mm | 0.8120 mm |
| Thread Angle | 60° | 60° |
Frequently Asked Questions (FAQ)
Q1. What is the difference between UNF and UNEF?
The difference is thread pitch. UNEF has more threads per inch than UNF. UNEF is typically used where precision and compact mounting are required.
Q2. What tolerance class is commonly used for 13/16-20 UNEF?
The most common tolerance class is:
- External thread: 13/16-20 UNEF-2A
- Internal thread: 13/16-20 UNEF-2B
Class 3A/3B is used when tighter precision is required.
Q3. Is 13/16-20 UNEF suitable for EMI filters?
Yes. It is commonly used in:
- Feedthrough capacitors
- Thread mount EMI filters
- RF shielding components
- Panel-mounted electronic assemblies
Its fine pitch allows compact installation and reliable mechanical retention.
Engineering Support CTA: Selecting a threaded EMI filter or feedthrough capacitor? Share the thread standard and size, panel thickness, voltage/current, capacitance, and environmental requirements with LCA engineers. View Thread Mount Feedthrough Filters
