Intronduction to Shop Prints


A presentation by professor Romel Cipriani

Classification of Engineering Drawings

What do you think is a working drawing?

A working drawing is an engineering drawing that provides all the information necessary to manufacture an object or a part and it is divided into two general classes: Assembly Drawings and Detail Drawings.

What information do you think has to be included on a working drawing?

  1. The full graphic representation of the shape of the object or part
  2. The figured dimension of the object or part
  3. Explanatory notes (both general and specific) on the object or part; for examples notes such as material, heat treatment, finish etc.
  4. There has to be a descriptive title on each drawing
  5. A description of the relationship of each part to the other in an assembly
  6. A parts list or bill of material.

Assembly Drawing

There are two types of Assembly Drawing: The main assembly drawing and subassembly drawing

MAIN ASSEMBLY DRAWING : the main assembly drawing shows a finished object, indicating all it component parts and how all the component part relate to each other. Note that only principle dimension dealing with assembly or installation are included on the main assembly drawing.

SUBASSEMBLY DRAWING : the subassembly drawing shows two or more parts joined together in the shop assembling procedure to form a unit of an object or piece of equipment, which is not itself a complete assembly.

DETAIL DRAWING : a detail drawing describes an individual part and contains all the information necessary to manufacture said part.

Standard Layout of a Blueprint

Standard Layout of a Blueprint

Title Block on a Working Drawing

Where is the Title Block located on a shop drawing?

A title block is necessary because an engineer or draftsperson must provide essential information without adding to the complexity of the drawing. This information is vital and must be place on the drawing where it can be accessed easily and clearly and this is where the title block becomes useful. Thus a title block contains information not directly related to the construction of an object, but which is necessary for its manufacture.

What kind of information do you think is contained in the Title Block of a drawing?

► Name of the company and location ► Name of part ► Part number, die number, forging number, etc. ► Drawing number assigned to the part ► Scale indicating the size of the drawing compared with the actual size of the part ► Drafting room info. Including names or initial of person responsible for project, date which the drawing was released etc. ► Material or material used in making the part ► Heat treatment information (if any) ► Final protective finish (if any) ► Tolerance (unless otherwise specified) that apply to all dimensions that do not have individual tolerance included with the basic dimension. ► Finished marks indicating which surfaces must be machine finish ► Shop notes (general or specific) which provide information and instruction that cannot be give conveniently by other mean ► Drawing revisions and/or changes made to the drawing

Example of a Title Block, a Material List and Revision Box

Example of a Title Block

Example of a Title Block

Example of a Material List

Example of a Material List

Example of a Revision Box

Example of a Revision Box

Understanding scale notation on a blueprint

  • A scale notation on a shop drawing allows for a comparison of between the drawing and the finished part
  • Large parts and assemblies may be drawn to a reduced scale to fit on paper
  • Very small parts may be drawn two or three times their actual size to show details clearly
  • The most common scales are full (actual), 2,4,1/2 and 1/4 times the actual size

Example of TYPICAL TOLERANCE

The following are typical decimal, fractional and angle tolerance values: Note you must always refer tolerance information and NEVER assume any tolerance.

Types of Projection

Central Projection:

  • In central projection, the projector converges to a point; this point represent the eye of the observer.
  • The result is that the size of the view varies depending on how far away the observer is for the object.
  • Because central projection distorts the actual shape of the object or part, it is not used in engineering drawings.
Central Projection

Central Projection

Parallel Projection:

  • Parallel projection does not have a converging point, instead the projector remains parallel to each other.
  • This type of projection gives the true size and shape of the object.
  • There are two types of parallel projection: Orthographic projection and Pictorial or oblique projection
  • Because the size of the object is not compromised in these types of projection they are primarily used in engineering drawings.
Parallel Projection

Parallel Projection

Orthographic Projection:

  • Orthographic projection show all the features of an object in their true shape
  • Orthographic projection are almost always used to make detailed drawings.
  • The three views of the object are usually give to show the three main dimension of the object: Length, Width and Height
Orthographic Projection

Orthographic Projection

Pictorial Projection:

  • Pictorial projection show all the feature of an object; however the image is greatly distorted
  • The basic purpose of a pictorial projection is to describe an object by showing all three of its dimensions in one view instead of three separate views like that of the orthographic projection
  • Because of it ability to distort objects pictorial projection are not often used in engineering drawings

Isometric Drawing:

  • Isometric drawings represent an object in three dimension (3D), about the three isometric axes that are 120 degrees apart
  • All lines that are parallel on the object are parallel on the drawing.
  • All vertical lines are shown as vertical
  • All horizontal lines are drawn at an angle of 30 degrees to horizontal
  • Isometric drawings may be dimensioned, but often do not have enough information to manufacture a part, thus they are used in conjunction with orthographic projection to clarify and aid in interpretation of a shop print
Isometric Drawing

Isometric Drawing

Oblique Drawing:

  • Oblique drawings also show an object in 3D
  • In an oblique drawing only the front of the object is shown in its true “size” and shape
  • The receding lines of the other two sides are drawn oblique at any angle–usually 30,45, or 60 degrees to the horizontal
  • Although the front view is shown in true “size” and shape, the receding sides are scaled less than their actual length— usually ¾ the scale of the front view
Oblique Drawing

Oblique Drawing

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