Short Answer:

Break lines are special lines used in engineering drawings to remove or shorten a portion of an object that is not necessary to show in full detail. They help in saving space and time while still showing the important features of the part. There are mainly two types: short break lines (zigzag) and long break lines (straight with zigzag or wave in between).

Break lines are important because they make the drawing clean, easy to read, and less crowded, especially for long or repetitive parts. They help the designer focus only on the critical features without drawing the entire part.

Detailed Explanation:

Break Lines and Their Use in Drawings

In mechanical engineering, many components are too long, repetitive, or symmetric to show fully on a standard-size drawing sheet. Drawing the whole part would not only waste space but also make the drawing difficult to read and understand. That’s why we use break lines—a simple and effective tool to shorten or cut out unimportant areas without affecting the meaning of the drawing.

Break lines are used to represent an interrupted view of a part, showing only the necessary features while skipping the middle portion or repetitive parts.

Types of Break Lines

There are mainly three types of break lines used in technical drawings:

1. Short Break Line
   • Used for small, irregular breaks.
   • Drawn as a freehand zigzag line.
   • Common in broken-out sections and small parts.
2. Long Break Line
   • Used for long objects like pipes, rods, shafts.
   • Looks like a straight line with a jagged or wavy middle section.
   • Cuts out a long middle portion to save drawing space.
3. Rectangular or Ruled Break Line
   • Sometimes used in rectangular or flat parts like plates.
   • Drawn with zigzag at the end of a straight line.
   • Suitable for uniform flat pieces.

These break lines help in removing non-essential areas without redrawing the full object.

Why Break Lines Are Used

1. To Save Drawing Space
   • Instead of drawing the full length, only the important areas are shown.
   • This allows the drawing to fit within the sheet.
2. To Improve Clarity
   • A clean and short drawing is easier to read and understand.
   • Avoids unnecessary repetition of same features.
3. To Focus on Key Features
   • Break lines help highlight critical parts like ends, holes, threads, grooves, etc.
   • Unimportant middle parts are removed.
4. To Avoid Redrawing Simple Repeats
   • If a pattern or section is repeating, one portion is drawn and break lines are used to show continuation.
5. To Show Internal Details
   • In some cases, break lines are used with section views to show cut surfaces clearly.

Standard Rules While Using Break Lines

• Break lines should be drawn clearly and differently from dimension lines or centerlines.
• Dimensions must be given for the actual full size, even if the drawing is broken.
• The break must not hide any important feature.
• When using break lines, it must be clear that the part continues beyond the visible area.

In CAD software like AutoCAD or SolidWorks, break lines can be added using specific commands or templates, and proper spacing and scaling are maintained automatically.

Examples of Use in Mechanical Drawings

• A long shaft with standard diameter → draw the ends and use a break line in between.
• Threaded rod or long bolt → show the threads at ends and break the middle part.
• Pipes or tubing → use long break lines to shorten view.
• Flat plates with repeated holes → show few holes and use break lines to indicate the rest.

Conclusion

Break lines are very useful in engineering drawings to shorten parts visually without removing any technical meaning. They help in saving space, improving clarity, and focusing attention on important features. By removing unnecessary portions from view, break lines make drawings simpler, cleaner, and more professional. Every mechanical engineer and drafter must know how and when to use break lines effectively.