M26 Threaded End Cap for Water Tap

M26 Threaded End Cap for Water Tap

A functional threaded end cap designed to seal M26 water tap connections. Perfect for temporarily or permanently closing unused tap outlets, preventing leaks during maintenance, or protecting threads during storage.

⚠ Important: This design requires the BOSL2 https://github.com/BelfrySCAD/BOSL2 library for OpenSCAD. See installation instructions below.

Features

• Proper M26 Internal Thread: Full ISO metric thread profile for secure fit

• Long Thread Engagement: ~24mm thread depth (86% of total height) ensures reliable sealing and grip

• Knurled Grip: 36 knurled ridges around the body for easy hand-tightening and removal

• Solid Top: 3.5mm thick sealed cap prevents any water leakage

• Print-Ready Design: No supports needed when printed cap-side down

Specifications

• Thread Size: M26 x 1.5 (standard metric coarse)

• Thread Length: ~24mm

• Overall Height: 28mm

• Outer Diameter: 34mm

• Wall Thickness: 3.2mm

• Top Thickness: 3.5mm

• Built-in Tolerance: 0.25mm for reliable fit after 3D printing

Print Settings

Recommended Settings:

• Layer Height: 0.2mm

• Infill: 20-30% (honeycomb or gyroid)

• Perimeters: 3-4 walls

• Top/Bottom Layers: 4-5 layers

• Material: PETG (water-resistant) or PLA

• Supports: None needed

• Orientation: Print with the cap (flat side) facing down on the build plate

Optional for Better Thread Quality:

• Enable "Detect thin walls" in your slicer

• Reduce layer height to 0.15mm for smoother threads

• Consider 100% infill for maximum strength if using for permanent installation

Customization

The design is created using BOSL2 library in OpenSCAD, making it easy to customize:

• Different thread pitch: Change pitch parameter (try 1.0 if your tap uses M26 x 1.0)

• Adjust tolerance: Modify tolerance value if the fit is too tight or loose (0.2-0.4mm range)

• Change height: Adjust cap_h for more or less thread engagement

• Remove knurling: Set knurl = false for smooth exterior

Application Notes

Before Installation:

• Clean the threads on both the tap and the cap

• Check that the thread pitch matches your tap (most common: 1.5mm)

• Test fit before tightening fully

Use Cases:

• Sealing unused outdoor tap connections

• Protecting threads during equipment storage

• Temporary closure during plumbing maintenance

• Replacement for lost original caps

Not recommended for:

• High-pressure applications above 2 bar

• Hot water connections above 60°C (PETG) or 50°C (PLA)

• Permanent installations requiring certified plumbing parts

Printing Issues?

Thread too tight:

• Increase the tolerance parameter to 0.3 or 0.35

• Check your printer's dimensional accuracy

• Sand the threads lightly with fine sandpaper

Thread too loose:

• Decrease tolerance to 0.2 or 0.15

• Check for under-extrusion

• Scale the model 101% in your slicer (X and Y only)

Knurling not printing well:

• Reduce print speed for outer perimeters

• Ensure proper cooling

• Increase wall line count

Requirements & Installation

Software

• OpenSCAD (version 2021.01 or newer): https://openscad.org/downloads.html

BOSL2 Library Installation

This design requires the BOSL2 library to work. Here's how to install it:

1. Download BOSL2:

   • Go to https://github.com/BelfrySCAD/BOSL2

   • Click the green "Code" button → "Download ZIP"

   • Extract the ZIP file

2. Place the BOSL2 folder:

   • Rename the extracted folder from BOSL2-master to just BOSL2

   • Place the BOSL2 folder in the same directory as the .scad file

   Your folder structure should look like this:

   your-project-folder/
   ├── m26_endkappe_lang.scad
   └── BOSL2/
       ├── std.scad
       ├── threading.scad
       └── ... (other BOSL2 files)
   

3. Alternative: OpenSCAD Libraries folder:

   • You can also place BOSL2 in OpenSCAD's library folder:

     • Windows: Documents/OpenSCAD/libraries/BOSL2/

     • Mac: Documents/OpenSCAD/libraries/BOSL2/

     • Linux: ~/.local/share/OpenSCAD/libraries/BOSL2/

Note: The BOSL2 folder must be named exactly BOSL2 (case-sensitive on Linux/Mac) for the includes to work!

License

This design is released under Creative Commons Attribution 4.0 International (CC BY 4.0). You are free to use, modify, and distribute this design, even commercially, as long as you provide attribution.

Changelog

Version 1.0 (Initial Release)

• M26 x 1.5 internal thread

• 28mm height with 24mm thread engagement

• Knurled grip surface

• Optimized for FDM printing