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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Lines and Their Uses in Orthographic Projection

A presentation by professor Romel Cipriani

Lines and Their Uses in Orthographic Projection

Family of Lines

Family of Lines

Object Line: Object lines are thick, solid lines that outline all surfaces visible to the eye

Hidden Lines: Hidden or invisible lines, consist of short evenly spaced dashes, outline hidden or invisible surfaces.

Center Line: Centerlines consist of alternating long and short evenly spaced dashes, with a long dash at each end and short   dashes at point of intersection.

Phantom Lines: Phantom lines are thin lines used to indicate alternate position of the parts of an object, repeated detail, or the   location of absent parts.

Dimension Lines: Dimension lines are short, solid lines that indicate the distance between two point on a drawing.  They terminate   with arrowheads at each end, and are broken to insert dimension.

Extension Lines: Extension lines are short, solid lines used to show the limits   of dimensions.  They may be placed inside or outside the   outside the outline of an object. They extend from an outline or surface, but do not touch it

Leaders: Leaders or leader lines indicate the part or area of a drawing to which a number, note, or other reference applies.  They are thin, solid lines and usually terminate in a single arrowhead.

Break Line:  Brake lines indicate that a part is broken out or removed either to (1) show more clearly the part or parts that lie directly   below the broken out part (2) to reduce the size of the drawing of a long part having uniform cross section so tat it   can be shown on a smaller sheet.

Section Lines: Section lines or crosshatch lines distinguish between two separate parts that meet a given point.  Having said this, section lines are used to depict a particular type of material. In assembly drawings, where many kinds of material may be used, individual parts may be crosshatched with the symbol for a particular material.

Cutting Plane Line: a cutting plane line consists of a heavy dash followed   by two shorter dashes.  At each end, it has a short   line at right angles to the cutting plane line terminating with arrowheads pointing in the direction from which the cut surface is viewed.

Section Lines

Section Lines

External and Internal Threads

External and Internal Threads

Sectional Views

A presentation by professor Gord Basa

  • Objective: Full Section, Half Section, Broken-Out or Partial Section, Rotated or Revolved Section, Auxiliary Sections, Assembly Sections, Offset Sections, Angular Sections, Sectioning Rules, and Sectional Symbols

A sectional view is obtained by imagining that a portion of the object has been cut away to expose internal lines and surfaces.  The path of the cut is considered the cutting plane.

  1. Full section: A view obtained by passing the cutting plane across the entire object exposing the whole inner surface.
  2. Half Section: A half section view is obtained by passing a cutting plane at right angles to each other along the centerlines of symmetrical axes of the object; thus exposing one-half of the inner surface.
  3. Broken-Out or Partial Section: At time it is necessary to show a single detail, or a related detail which exist in the interior of the object.  If only these details (internal) are all that is needed then the broken-out section view is used.
  4. Rotated or Revolved Section: A rotated section is made directly on one of the principle exterior outline view of the object, these may be bars, ribs, webs etc.  Note the cutting plane passes perpendicular to the centerline of the part to be sectioned.  The resulting section is then revolved 90 degrees into the plane of the paper.
  5. Removed or Detail Section: These view are similar to rotated section but are detached from the object and positioned along the center line of the object.
  6. Offset Section: When a single cutting plane is not possible to produce a sectional view, then several cutting planes are employed in different directions to cut through the object.
  7. Angular Section: Angular section show detail of an object where the cutting plane used is not 90 or 180 degrees.
  8. Single Auxiliary View: A single auxiliary view is made by projecting the inclined surface in a plane parallel to it and perpendicular to one of the regular plane.  This enables the viewer to see the surface as it actually appears when from 90 degree angle.

Sectioning Rules

  • Thin sections, such as sheet metal, structural shapes, packing gaskets, etc. are shown as solids in a sectional view.  That is they have narrow spaces left between the thickness of these parts.
  • When a part is sectioned in more than one place, the spacing and direction of the cross-hatching is the same in all sectioned area.
  • When two adjacent parts are shown in sectional view, their cross-hatching are in opposite direction.
  • When three adjacent parts are in section, two of them will have 45 degree cross-hatching in opposite direction.
  • If cross-hatching using standard angles would appear nearly parallel to an object line of the part, then different angles must be used.
  • If cross-hatching using standard angles would appear nearly parallel to an object line of the part, then different angles must be used.
  • Invisible object line and details behind the cutting plane are not shown on sectional views unless they are needed to clarify the drawing.
  • When a cutting plane passes through a rib, web, or similar parallel portion of the object the cross-hatching is omitted from those portions.  In such cases, the cutting plane is seen to pass just in front of the rib or web.
  • Sectional view reveal an object’s inner detail by graphically removing portions of the surface.  This is done in a standard way by using a cutting plane line or brake line.  Either way, the purpose of sectional views is to simplify the drawing be elimination hidden lines (Garvey, Lonny. New How to Read Shop Prints & Drawing.  National Tooling and Machining Association, United States of America, 2002. pg. 61)

Introduction to Jigs and Fixtures

A presentation by professor Gord Basa 

What is the definition of a machine tool?

  • A machine tool is defined as a piece of equipment driven by an electrical motor.

What is the definition of a cutting tool?

  • A cutting tool is defined as a high alloy steel machined to a form which will facilitate metal cutting.

The designer must satisfy the following 7 objectives:

  1. Provide simple, easy to operate tools for maximum efficiency.
  2. Reduce manufacturing expenses by producing parts at the lowest possible cost.
  3. Design tools that consistently produce parts of high quality.
  4. Increase the rate of production with existing machine tools.
  5. Design the toll to make it foolproof and to prevent improper use.
  6. Select material that will give adequate tool life.
  7. Provide protection in the design of the tools for maximum safety of the operator.

What is a “Production Plan”?

  • A production plan is an itemized list of the manufacturing   operations and the sequence of the operation chosen by the   process planning engineer.

What do you think are the requirement to become a tool designer?

  • The ability to operate machine tools, read blueprints and is able to make mechanical drawings to full scale.

Jigs and Fixtures

  • Jigs and fixtures are production workholding devices used to manufacture duplicate parts accurately
  • They maintain the position and alignment between cutting tools and workpieces
  • Jigs and fixtures are closely related and are often confused with one another
  • A jig is a device that guides a cutting tool used in a machining operation.  It can hold or support a workpiece if necessary.
  • A fixture is a device that locates, holds and supports a part so that machining operations can be performed

There are two classes of jigs:

  • Boring jigs are used to bore holes that are too large to drill, or must be made an odd size
  • Drill jigs are used to drill, ream, tap, chamfer, counterbore, countersink, reverse spotface or reverse countersink.

Types of Jigs

  • There are two general types of jigs, open and closed Open jigs are simple and only used on one side of the part Closed, or “box” jigs are used when the machining is done on more than one side
  • Template jigs are normally used for accuracy, but not speed.  They fit over or onto the workpiece, but are usually not clamped.  They are inexpensive and simple, and may or may not have bushings.
  • Plate jigs are like template jigs, but have built-in clamps to hold the work.  Plate jigs sometimes have legs and are then called table jigs.
  • Sandwich jigs are like plate jigs, but with a back plate.  This is advantageous to keep thin materials from warping.  They may or may not have bushings and may have locating pins to locate the plates to one another.
  • Angle-plate jigs hold parts that are machined at right angles to their mounting locators
  • Modified angle-plate jigs hold parts at angles other than 90 degrees.
  • Box jigs, or “tumble jigs” totally surround the part and allow the part to be machined on every surface without repositioning the jig.
  • Channel jigs are “C” shaped.  They hold a part on two sides and allow machining on the third side.
  • Leaf Jigs are small box jigs with a hinged leaf to allow for easier loading and unloading.

Classification of Fixtures

  • Fixtures are classified according to the machine on which they are used.  A fixture designed for use on a milling machine is a milling fixture.  A fixture designed for use on a straddle mill is a straddle-milling fixture.

Types of Fixtures

  • Generally speaking, fixtures are larger, heavier and stronger than jigs.
  • Plate fixtures are made from flat plates with locators and clamps.  They are simple, adaptable and very popular.
  • Angle-plate fixtures are a variation of plate fixtures where the part is machined at a right angle to the part locators.
  • Modified angle-plate fixtures can be used when other angles are needed.
  • Vise-jaw fixtures are used for small parts.  Standard vise jaws are replaced with jaws formed to fit the part.  These are the least expensive type of fixture to make.
  • Indexing fixtures are similar to indexing jigs.
  • Multistation fixtures are used for high production runs where the machining cycle must be continuous.  The simplest type of multistation fixtures are duplex fixtures and are designed to hold two parts.  As one part is being machined, the other can be reloaded.  Duplex fixtures can be made to rotate between cycles.
  • Profiling fixtures are used to guide tools around irregular contours.

The key to jigs and fixtures is the alignment between the cutter and other tools relative to the part that has to be machined.

Jigs and fixtures are designed to hold, locate and support parts ensuring that the part is drilled or machined to specifications.

Basic Blueprint Reading and Tolerancing

What is a Blueprint?

  • A blueprint is a technical drawing, or a paper reproduction of a technical drawing, documenting an architecture or an engineering design.
  • In the machining industry it details the design of machined or manufactured parts. Generally, “blueprint” is the term used that refers to any detailed plan.

What’s in a Blueprint?

  • The Title Block: Contains general information about the part
  • Company name • Part Name •Part Number • Drawing Revision Number • Scale • Grid • Tolerancing Standards • Materials List • Drawing Date • Approvals and Signoffs
  • Standard Tolerances Unless Otherwise Specified
  • It is impossible to manufacture to exact sizes, so tolerances are specified in the title block

Tolerances

  • Upper Tolerance Limit: A given dimension with the “+” tolerance added to it.
  • Lower Tolerance Limit: A given dimension with the “-” tolerance subtracted from it
  • Bilateral Tolerance:  A tolerance given as a “+” and “-” dimension. Bilateral tolerances do not have to be equal in each direction.
  • Unilateral Tolerance:  A tolerance given in either the “+” or the “-” direction.

Line Types: Different lines have different meanings.

  • Object Lines: Heavy, solid lines to indicate visible edges.
  • Hidden Lines: Short dashes to indicate hidden features.
  • Dimension Lines: Thin, solid lines with arrow heads showing the distance being measured.
  • Extension Lines: Thin, solid lines that extend from a feature without touching it.
  • Center Lines : Thin, alternate long and short dashes.  Not part of the object, it indicates the centre position of a feature.
  • Leader Lines: Similar to a dimension line, it points to a surface and calls out a dimension.
  • Break Lines: Used to remove redundant information to save space on blueprints.
  • Freehand Break Lines: Used to indicate short breaks.
  • Ruled/Z Lines: Used to indicate longer breaks and are the more common of the two.
  • Curved Break Lines: indicate cylindrical breaks

Symbols: Different symbols have different meanings.

  • Diameter (ø): Indicates the diameter of a round feature.
  • Radius (R): The letter “R” is used to indicate the radius of a round feature.

Dimensioning

  • Chamfers: Note that when indicating a 45º chamfer, the distance given is the distance from the edge of the part to the start of the chamfer.
  • Counterbore
Couterbores

Counterbore

  • Countersink
Coutersinks

Countersink

  • Standard Threads: Ex) ½ – 13 UNC – 2B – LH x .88 DEEP : ½ = The major diameter of the thread, 13 = TPI, threads per inch, UNC = Unified Coarse Thread standard, UNF = Unified Fine Thread standard, 2B = Thread class (for “fit”), LH = Left Hand, .88 DEEP = Full Thread Depth

Views in Blueprints

1. Isometric:

  • Represents the part in a three-dimensional view.
  • Aids the blueprint reader in interpreting the drawing.

2. Orthographic:

  • This is a means of representing a part with separate, two-dimensional views.
  • A basic blueprint can have a top, front and side view as indicated in the illustration.
  • More views can be added, such as bottom, left and back views.
  • Orthographic views, when properly done, are “hinged” as is the home drawing to the left.
  • Within this exists the textbook “Top, Front, Right” views that serve as a basis for many Blueprints.

3. Auxiliary Views

  • An auxiliary view is a view that represents the true size and shape of an inclined surface.  Auxiliary views are added to drawings when it is impossible to show true shapes in standard, orthographic views.

4. Partial Auxiliary View

  • A partial auxiliary view is an auxiliary view in which only the details of an inclined surface are represented.

5. Primary and Secondary Auxiliary Views

  • A secondary auxiliary view can be projected from a primary auxiliary view to show true shapes and locations of part features.
  •  Secondary auxiliary views are often required when there are two or more inclined surfaces in a blueprint.

Sections

Full Sections

  • A full section view results from an imaginary cut through the entire length of a part.
  • The imaginary cut is the cutting plane line, labeled as “AA” to the right.
  • Sectioned surfaces are indicated by a series of solid, slanted lines.

Half Sections

  • A half section view results from an imaginary cut through a portion of a parts length.