THREADS & FASTENERS - Drawing Screw Threads

Lecture content

There are three methods of representing screw threads on a drawing.

 

  • Detailed
  • Schematic
  • Simplified

 

Screw thread representation present in this chapter is in accordance with the ASME Y14.6-2001 standard.

 

Detailed Representation

 

A detailed representation is a close approximation of the appearance of an actual screw thread.

 

What do you think the pros and cons are for this type of representation? (Add interactivity)

 

Detailed threads

 

Lecture content

Schematic Representation

 

The schematic representation uses staggered lines to represent the thread roots and crests.

 

What do you think the pros and cons are for this type of representation? (Add interactivity)

 

Schematic External

 

Schematic Internal

 

Lecture content

Simplified Representation

 

The simplified representation uses visible and hidden lines to represent the major and minor diameters.

 

What do you think the pros and cons are for this type of representation? (Add interactivity)

 

Simplified External

 

 

Simplified Internal

 

Lecture content

Drawing Screw Threads

 

Thread tables in the appendix of the Engineering Graphics Essentials book can be used to look up value for the;

 

  • Pitch
  • Minor diameter
  • Tap drill diameter

 

If screw thread tables are not available, the minor diameter can be approximated as 75% of the major diameter.