1 9/16-18 UNEF Thread Quick Specifications
| Parameter | Specification | |
| Thread Standard | Unified Thread Standard (UTS) | |
| Thread Series | UNEF | |
| Nominal Size | 1 9/16 | |
| Thread Designation | 1 9/16-18 UNEF | |
| Threads Per Inch (TPI) | 18 | |
| Major Diameter | 1.5620 in | 39.675 mm |
| Pitch | 0.0556 in | 1.4120 mm |
| Pitch Diameter | 1.5259 in | 38.758 mm |
| Minor Diameter | 1.4958 in | 37.993 mm |
| Thread Height | 0.0301 in | 0.7650 mm |
| Addendum | 0.0180 in | 0.4570 mm |
| Thread Angle | 60° | |
| Common Classes | 2A / 2B | |
| Typical Use | Precision electronic assemblies | |
Introduction
The 1 9/16-18 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.
The 1 9/16-18 UNEF thread has a nominal major diameter of 1.562 inches (39.675 mm), a pitch of 0.0556 inches (1.412 mm), and 18 threads per inch (TPI). The most common tolerance class is 2A for external threads and 2B for internal threads.
This page provides a complete engineering reference for 1 9/16-18 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 1 9/16-18 UNEF specification helps ensure proper mechanical compatibility, reliable installation, and long-term performance. The threaded mounting design ensures excellent grounding to the equipment enclosure, improving shielding effectiveness and overall EMC performance.
Quick Answer:
The 1 9/16-18 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 1 9/16-18 UNEF thread is a Unified National Extra Fine (UNEF) screw thread defined by the Unified Thread Standard (UTS).
The designation means:
- 19/16 indicates the nominal major diameter
- 18indicates 18 threads per inch (TPI)
- UNEFindicates Unified National Extra Fine thread series — characterized by the finest pitch for its nominal diameter within the Unified thread series, offering maximum precision and vibration resistance
1 9/16-18 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: 1 9/16-18 UNEF-2A
Internal Thread: 1 9/16-18 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: 1 9/16-18 UNEF-3A
Internal Thread: 1 9/16-18 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
1 9/16-18 UNEF vs Similar Thread Sizes
Engineers often need to determine whether another thread specification can replace 1 9/16-18 UNEF.
1 9/16-18 UNEF vs M39 × 1.5
| Parameter | 1 9/16-18 UNEF | M39 × 1.5 |
| Standard | Unified | Metric ISO |
| Major Diameter | 39.675 mm | 39.00 mm |
| Pitch | 1.4120 mm | 1.500 mm |
| Pitch Diameter | 38.758 mm | 38.026 mm |
| Minor Diameter | 37.993 mm | 37.376 mm |
| Thread Height | 0.7650 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 1 9/16-18 UNEF?
The most common tolerance class is:
- External thread: 1 9/16-18 UNEF-2A
- Internal thread: 1 9/16-18 UNEF-2B
Class 3A/3B is used when tighter precision is required.
Q3. Is 1 9/16-18 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
