Screw & Threads

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

Printing

Freecad

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see also

Freecad knows ISO screws size - see Fasterner Workbench

And 0.20 can make hole with thread.

Creating thread

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:

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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

[Notes]

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Hex Nut Capture Socket sizing for 3D Printing

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.

Screw Model

Written on September 4, 2019, Last update on April 27, 2024
screw 3dmodel 3dprint openscad freecad cnc