3d Computer Graphics and Screw Thread
How to Model Screw with AutoCAD (If You Must)
A realistic screw thread is possible but comes at a cost of time and effort
By Jim Patrick
A recurring topic in CAD newsgroups is making 'real' screw threads. CAD users insist on modeling parts that are accurate to every detail down to thousandths of an inch. Hours may be spent on this endeavor. This can lead to much frustration.
Don't Do It
My usual answer when asked how make real screws is "Don't do it!" Draw them in 2D. AutoCAD strains itself on solids. A realistically modeled length of thread can bogs down most computers. And when it gets right down to it, a true screw thread is impossible in AutoCAD. Some CAD programs, like SolidWorks can make true threads, but still file size balloons and performance suffers.
Do it In the Flat
A 2D representation of a screw is usually sufficient to convey its use in an assembly. A 2D depiction of a screw thread can look quite real. The time spent on creating a realistic 3D model as well as the time needed to then print it with hidden lines removed is better spent on something productive.
Table 1: Representing screw threads in 2D.
Method 1: Not very realistic.
Fast. Just arrayed lines.
Method 2: Semi-realistic
Arrayed lines and zig-zag.
Method 3: Realistic
Teeth offset, then arrayed lines
Method 4: Real
Splines and overlaps. Lots of time. Really real
Actual model for comparison
My personal preference for representing threads in 2D is method 2 or 3.
The first example just doesn't look like threads.
It'll be a cold day when I use method 4 and use splines!
Showing Threads in Isometric Views
The standard flat drawings aren't appropriate all the time. Perspectives, assembly manuals, and presentations are a some of those times. One firm covered most of their bases by including an isometric view in each of their block drawings. Just the two isometric views -- when rotated or flipped -- can account for many different perspectives.
But
A realistic screw thread is possible but comes at a cost of time and effort
By Jim Patrick
A recurring topic in CAD newsgroups is making 'real' screw threads. CAD users insist on modeling parts that are accurate to every detail down to thousandths of an inch. Hours may be spent on this endeavor. This can lead to much frustration.
Don't Do It
My usual answer when asked how make real screws is "Don't do it!" Draw them in 2D. AutoCAD strains itself on solids. A realistically modeled length of thread can bogs down most computers. And when it gets right down to it, a true screw thread is impossible in AutoCAD. Some CAD programs, like SolidWorks can make true threads, but still file size balloons and performance suffers.
Do it In the Flat
A 2D representation of a screw is usually sufficient to convey its use in an assembly. A 2D depiction of a screw thread can look quite real. The time spent on creating a realistic 3D model as well as the time needed to then print it with hidden lines removed is better spent on something productive.
Table 1: Representing screw threads in 2D.
Method 1: Not very realistic.
Fast. Just arrayed lines.
Method 2: Semi-realistic
Arrayed lines and zig-zag.
Method 3: Realistic
Teeth offset, then arrayed lines
Method 4: Real
Splines and overlaps. Lots of time. Really real
Actual model for comparison
My personal preference for representing threads in 2D is method 2 or 3.
The first example just doesn't look like threads.
It'll be a cold day when I use method 4 and use splines!
Showing Threads in Isometric Views
The standard flat drawings aren't appropriate all the time. Perspectives, assembly manuals, and presentations are a some of those times. One firm covered most of their bases by including an isometric view in each of their block drawings. Just the two isometric views -- when rotated or flipped -- can account for many different perspectives.
But