M18 ×1.5 Thread Overview
M18 × 1.5 is an ISO metric fine thread with a nominal diameter of 18 mm and a thread pitch of 1.5 mm. The smaller pitch provides finer adjustment and allows more threads to engage over a given threaded length.
Compared with the standard M18 × 2.5 coarse thread, M18 × 1.5 is generally used where positioning accuracy, adjustment resolution, or increased thread engagement is important.
M18 × 1.5 Thread Dimensions
| Parameter | Specification | |
| Thread Standard | ISO Metric Threads | |
| Major Diameter | 18.0mm | 0.7087 in |
| Pitch | 1.5 mm | 0.0591 in |
| Pitch Diameter | 17.026 mm | 0.6703 in |
| Minor Diameter | 16.376 mm | 0.6447 in |
| Thread Height | 0.812 mm | 0.032 in |
| Addendum | 0.487 mm | 0.0192 in |
| Thread Angle | 60° | |
Understanding the M18 × 1.5 Designation
The designation identifies the basic geometry of the thread:
- M= ISO Metric Thread
- 18= Nominal major diameter of 18 mm
- 5= Thread pitch of 1.5 mm
The pitch should be stated when specifying the thread because the same nominal M18 diameter can be manufactured with different pitches. Writing M18 × 1.5 removes ambiguity during design, machining, and purchasing.
Characteristics of M18 × 1.5 Fine Thread
- Smaller pitch than the standard M18× 5 coarse thread.
- Finer axial adjustment and greater adjustment resolution.
- More engaged threads over the same threaded length.
- Useful where available axial space is limited.
- Suitable for precision mechanical assemblies and fine adjustment mechanisms.
M18 × 1.5 Thread Tolerance Classes
Thread tolerance classes define the permissible dimensional variation and determine how mating external and internal threads fit together. ISO metric fine threads, a complete tolerance designation combines a numerical tolerance grade with a tolerance-position letter.
Example: M18 × 1.5 – 6g
- 6 — Tolerance grade.
- g — Tolerance position for an external thread.
The corresponding internal thread is typically specified as M18 × 1.5 – 6H.
| Thread Type | Common Class | Typical Application |
| External Thread | 6g | General-purpose screws and bolts |
| Internal Thread | 6H | General-purpose tapped holes and nuts |
| External Thread | 4g6g | Precision mechanical assemblies |
| External Thread | 8g | Loose fit or coated fasteners |
| Internal Thread | 5H | Higher positioning accuracy |
M18 × 1.5 vs. M18 × 2.5
M18× 1.5 and M18 × 2.5 have the same nominal major diameter, but their pitches are different. The choice depends on the required assembly characteristics and application.
| Feature | M18 × 1.5 | M18 × 2.5 |
| Thread Type | Fine thread | Standard coarse thread |
| Pitch | 1.5 mm | 2.5 mm |
| Adjustment | More precise | Faster |
| Thread Engagement | More threads per length | Fewer threads per length |
| Assembly | Suitable for precision adjustment | Generally easier and faster |
| Typical Use | Precision assemblies and fine adjustment | General-purpose fastening |
Typical Applications
M18 × 1.5 fine threads can be used in applications where controlled adjustment, positioning accuracy, or compact threaded engagement is required. Examples include:
Optical instruments
- Precision measuring devices
- Fine adjustment mechanisms
- Precision mechanical assemblies
By comparison, M18 × 2.5 coarse threads are commonly selected for general-purpose fastening applications, including industrial equipment, enclosures, and control panels.
Frequently Asked Questions (FAQ)
Q1. Is M18 × 1.5 a standard thread?
Yes. M18 × 1.5 is an ISO metric fine-thread configuration.
Q2. Is M18 × 1.5 the same as M18?
Not exactly.
M18 identifies the nominal diameter, while 1.5 specifies the pitch. The pitch should be included when a fine thread is required.
Q3. What is the difference between M18 × 1.5 and M18 × 2.5?
The difference is thread pitch.
Q4.What does 6g mean for an M18 × 1.5 thread?
6g is a commonly used tolerance designation for an external ISO metric thread, combining tolerance grade 6 with tolerance position g.
Q5.What is the typical internal-thread designation?
The corresponding internal thread is typically specified as M18 × 1.5 – 6H.
Q6. Can LCA provide EMI filters with M18 threads?
Yes. LCA supports customized mechanical designs involving metric and inch thread configurations.
Customization options include:
- Thread size
- Housing dimensions
- Electrical parameters
- Sealing structure
- Plating options
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
Related Engineering Resources
- Unified Thread Standard
- UNC Threads
- UNF Threads
- UNEF Threads
- Metric Threads
- Metric Coarse Threads
- Metric Fine Threads
- #4-40 UNC Thread Dimensions
- 1/4-28 UNF Thread Dimensions
- 5/16-32 UNEF Thread Dimensions
- 5 Thread Dimensions
- M5 Thread Dimensions
- M4 Thread Dimensions
- M6 Thread Dimensions
- M7 Thread Dimensions
- M8 Thread Dimensions
- M9 Thread Dimensions
- M11 Thread Dimensions
- M12 Thread Dimensions
- M14 Thread Dimensions
- M16 Thread Dimensions
