In traditional CAD systems modelling screw threads is discouraged because it puts a big load on the modelling kernel, as well as on the rendering of the shapes… However, with the popularization of additive manufacturing (3D printing), there is now a real need to model 3D threads, in order to print them exactly as designed. - Thread for Screw Tutorial / Thread Anatomy- (In less than 5 min!)

This article is a guide to using screws in 3D printed SLA parts. There are many other ways to attach multiple 3D printed parts together, but if you need to repeatedly attach and detach components and want robust mechanical fastening, there’s no real replacement for genuine metal threads. - Adding Screw Threads to 3D Printed Parts

Thread Calculator

• METRIC THREAD DIMENSIONS CALCULATOR
• Metric Thread Table Chart

Printing

• You should be using Cura’s experimental slicing tolerance setting - Exclusive this change the way the model is sliced, supporting a better fit regarding screw/thread constraint

Freecad

• FreeCAD_Fastener_holes - creates shapes to act as holes when cut to other shapes

see also

• FreeCAD Threaded Hook
• How to make threaded parts in FreeCAD .17

Freecad knows ISO screws size - see Fasterner Workbench

And 0.20 can make hole with thread.

• 3D Printed FreeCAD Threads - FreeCAD 0.20 Holes - juste use a holes + a clearance of at least 0.30mm
  • FreeCAD 0.20 : Taraudages et filetages pour impression 3D
• Filetage semi-rond pour impression 3D
  • spirale + scale*1.05 + cut

Creating thread

• ThreadProfile Workbench
  • Thread Maker macro

Cutting a thread with bolt gives you a “negative” bolt thread which is mechanically incorrect. To make a “real” threaded hole, there is a special arbitrary length “tap” rod that you then cut from your object:

If it is made for 3D printing, there is a section in the settings that lets you tweak tolerances such that printed parts will match each other.

For tapped screw hole,

when creating holes in part-design workbench

• select ISO metric regular profile
• select Size (ex M3)
• select Threaded => this will give a hole diameter for tap drill (ex for M3 screw, it’s 2.5mm)

Standard Thread size: M3 2.5mm (hole) x 0.5mm (thread pitch)

Custom Definition can be added to the workbench - see Cut Type Definitions

• Taraudage in Freecad 0.20 - avec custom clearance
• Thread for Screw Tutorial
• Designing a 3D printed filament spool holder

[Notes]

• 3dprint screws - set scale settings to 3dprinting in the Fasteners Preferences

• model a screw in freecad

Hex Nut Capture Socket sizing for 3D Printing

• Embedding Nuts in 3D Printed Parts for Hidden Fastener Strength
• 3D Printing Threads and Screws – Simple Guide

Openscad

undersized holes

When using cylinder() with difference() to place holes in objects, the holes will be undersized. This is because circular paths are approximated with polygons inscribed within in a circle. The points of the polygon are on the circle, but straight lines between are inside.

• undersized circular objects
• Polyholes

Screw Model

• threadlib - a library of standard threads for OpenSCAD.
• NopSCADlib/Screws

• OpenSCAD Screw Holes