(4:12) Create a Helix object (Create-Polygon Primitives-Helix)
(4:53) Adjust Helix object attributes as desired

• Coils: 10.6
• Height: 1.0
• Width: 1.015
• Radius: 0.05
• Subdivisions Axis: 3
• Subdivisions Coil: 50+
  
  

(7:55) Bevel the helix

• Double-click center edge of helix to select edge loop
• Bevel (Edit Mesh-Bevel)
• Fraction: 0.168
• Segments: 1
• Depth: 1
  
  

(9:40) Double-click the other edge loops to select. Translate and scale as desired to form the “trough” of the threads

• Control-click on the Y-Axis scale handle to proportionately scale on the X and Z-axes
  
  

(12:50) Delete the end caps of the helix object using Face Select mode
(13:10) Delete all inner faces of the helix object

• Shift-select one inner face of the helix, then double-click the face next to it to select a face loop
  
  

(13:50) Bridge both ends of the helix

• Shift-select 2 edges
• Shift-Right-click–Bridge
• Bridge Type: Linear Path
• Divisions: 0
  
  

(14:55) Bridge all gaps in the helix

• Double-click an inner edge to select the edge loop
• Control-select the ends to de-select
• Shift-Right-click–Bridge
• As long as there are an even number of edges selected, the bridge operation is smart enough to bridge all gaps in one action
  
  

(16:30) Add taper to the threads

• Double-click the end edge loop
• Press “B” to use Soft Selection mode
• Hold down B, Right-click and drag to adjust soft selection area
• Adjust tool settings in Tool Settings–Soft Selection
• Be sure to use Linear Falloff Curve
• Control-click on the Y-Axis of the scale tool to proportionately scale the X and Z-axes
  
  

(18:50) Cut the end

• Switch to top view and vertex mode
• Use the Multi-cut tool to slice across the mesh (Shift+Right-Click–Multi-Cut)
• Delete excess faces
  
  

(22:30) Cap the end

• Select edge loop
• Extrude (Shift+Right-click–Extrude)
• Fill Hole (Shift+Right-click–Fill Hole)
• Poke Face (Shift+Right-click–Poke Face)