Part A. With the items correctly assembled draw, twice full size, in either first or third angle orthographic projection: (1) a sectional front view on the cutting plane A – A; (2) a plan. Do not show hidden detail of the nut. Part B. Print, using block capital letters: (1) the title LEVER SUB-ASSEMBLY; (2) the scale used for your drawing; (3) the projection you have used. Insert on your drawings six main dimensions in accordance with the standard method of dimensioning (Fig. 6). Assume any details or dimensions not given. Southern Regional Examinations Board
The Correct Answer and Explanation is:
Certainly! Your question relates to a classical mechanical drawing exercise, specifically creating an orthographic projection of a lever sub-assembly with sectional views and dimensioning. Let’s break this down carefully.
Part A: Drawing Instructions
What is required:
- Draw twice full size — The scale is 2:1 (twice the actual size).
- Orthographic projection — You may choose first angle or third angle projection. (These are standard conventions used internationally.)
- Two views:
- Sectional front view on cutting plane A – A
This means you imagine a “cut” along plane A–A, remove the front portion and show the internal features in that sectional view. - Plan view (top view)
- No hidden details of the nut — So when drawing the nut, do not show hidden lines (edges not visible from that view).
Part B: Annotations and Dimensions
You must print on the drawing:
- Title: LEVER SUB-ASSEMBLY (in block capital letters)
- Scale: e.g., “Scale 2:1”
- Projection used: State either “First Angle Projection” or “Third Angle Projection”
Also, insert six main dimensions using the standard method of dimensioning (such as those shown in the figure referenced).
Explanation of the Drawing Process (300 words):
Orthographic projection is a fundamental technique in technical drawing, where a three-dimensional object is represented by several two-dimensional views. The two most common projection methods are first angle and third angle projections:
- First Angle Projection: The object is placed between the observer and the plane of projection. It’s mainly used in Europe and Asia.
- Third Angle Projection: The plane is between the observer and the object, commonly used in the USA and Canada.
In this exercise, you are tasked with producing two views of the lever sub-assembly: a sectional front view along a specified cutting plane and a plan (top) view. The sectional front view means you have to imagine the object is sliced along plane A–A, and the front part removed to expose the internal components (such as the lever’s interior and perhaps the bolt or pin assembly). This is essential in mechanical drawings to reveal internal details that cannot be seen externally.
The plan view is the direct top-down view, showing the layout and overall shape without internal cutting.
Since the nut’s hidden details are omitted, when you draw the nut, you only show visible edges, avoiding unnecessary complexity in the drawing.
The drawing must be scaled twice full size (2:1), meaning all dimensions should be doubled compared to actual size to improve clarity.
Dimensioning follows international standards (ISO, ANSI), ensuring the placement of dimension lines, extension lines, and numerical values clearly and unambiguously communicates the size and location of features. Dimensions should be chosen to convey the critical sizes required to manufacture or inspect the part—such as length, width, hole diameters, thicknesses, and distances between features.
Finally, the title block information (title, scale, and projection method) ensures that the viewer understands what the drawing represents, the scale for measuring, and the projection method used to interpret the views correctly.
Summary: What to produce
- Sectional front view (cut along A–A, show internal details)
- Plan view (top view)
- Scale 2:1 (twice full size)
- Projection method noted (first or third angle)
- Title: LEVER SUB-ASSEMBLY
- Six main dimensions added per standard dimensioning practice
- Nut hidden details omitted
If you want, I can help you create a detailed sketch or CAD-style diagram based on a lever assembly you describe or provide a sample lever drawing template for practice. Would you like that
