ME 186 Midterm

Tap and Die-Threading

Tap used to provide internal screw threads on an existing hole Die used to provide external threads Tools called a tap and a die Thread callouts: UNJF, ...., 2A vs. 2B

One Rule of Dimensioning

"Dimension the drawing so it is clear and not confusing to the reader"

Standard Engineering Sheet Sizes are:

- "A" size: 8.5" x 11" [Generally used for Specifications & Standard Part Drawings] - "B" size: 11" x 17" - "C" size: 17" x 22" - "D" size: 22" x 34" - "E" size: 34" x 44"

Standards:

- ASME Y14.1 Decimal Inch Drawing Sheet Size and Format - ASME Y14.1M Metric Drawing Sheet Size and Format - ASME Y14.34 Associated Lists • Print reader should start with Title Block which include information about: - Part number, part name, last revision date, construction materials, tolerance, etc.

Knurls

- Covered by ASME B94.6 - Called by pitch, type, diameter before and after knurl

Interchangeable Manufacturing

- Duplicate parts can fit and still function - Parts are manufactured within specified limits of size.

Extension Lines

- Extend from the part or the feature being dimensioned - A small gap must be left between part and extension line

Keys/Keyseats/Keyways

- Keys, type of fasteners used to prevent rotation of gears, pulleys and rocker arms on a rotating shaft - Keyseats, the cut on the shaft where the key will be placed - Keyway, cut in the hub where the key will slide

Counterdrill

- Note: the depth measurement on the callout are for the full‐diameter distance (i.e. does not include the angled portion)

Selection of Views:

- Only views clearly describing the shape of the object should be drawn - Select views containing the fewest hidden lines - Draw the object in the its functioning (operating position) - Draw the view best describing the shape of the object as the Front View

Reamed Holes

- Reamers are used to slightly enlarge an existing hole • Results in a very true hole with smooth finish and tight tolerance - To create a reamed hole • The hole is drilled slightly smaller (.010" to 0.025") • Then reamed to finish size

Title Block Elements

- Sheet area [D] (SHEET n OF x) - Size area [E](sheet size used in printing) - Weight area [F] - Scale area [G] = Expressed as "Paper : Real " • "FULL" means 1:1 • "HALF" means 1:2 • 2:1 means, every unit on the part is shown twice as big on the print • "As Noted" means there are several scales used on the drawing. - CAGE CODE [H] Commercial and Government Entity • It is a 5 digit alpha numeric code: - For example: 02AB3 • Not used by most commercial entities - Signature area [J] • Drawn engineer who created the drawing • Checked engineer who checked the drawing for Completeness, Clarity and Accuracy. • Approved additional approval • Issued the person who released the drawing

Purpose of a drawing is to show

- Size - Shape - Information on how to make part

Drawing sheet size chosen depends on the part's:

- Size & Complexity

Local Notes/Flag Notes

- Specific notes, callouts - Applies only to certain features or areas on the drawing - Positioned near the feature or the area, where a leader line is used to indicate the feature or the area - It may be listed along with "General Notes" but with a flag (triangle, hexagon, etc...)

Necks and Undercuts

- Surfaces for retaining rings - Transition between two features

Recommendations (might not be needed for exam)

- The first dimension should be 3/8" away from the view and subsequent dimensions should be another 1/4" or more beyond the previous one. - It is permissible for extension lines to cross each other - It is desirable that dimension lines don't cross each other - Line sub‐dimensions up with each others - Avoid crossing dimension lines with leader lines - Small dimensions create the need to break the dimension line into two pieces.

Tolerance

- The total amount by which a dimension can vary - Applied to size and location dimensions

Hidden Lines

- Thin, short dashes spaced closely together. - Used to show edges, surfaces, and features not visible in a particular view.

Title Block Elements CONT

- Tolerance area indicate the general tolerance valued for x.x, x.xx and x.xxx to be applied unless tolerance is called on the face of the drawing (within a dimension) - Finish area indicate general finish requirements such as paint. - Materials area indicate materials used to make the part. - Heat treatment area indicate heat treatment and hardness.

Notes on Engineering Drawings

- Type of the note is determined by the application of the note and how it is placed on the drawing - There are two types of notes defined by ASME Y14.100

Types and Locations of Tolerance Callouts

- Unilateral Tolerances ‐‐ Min / Max Tolerances - Bilateral Tolerances ‐‐ Title Block Tolerances • Equally Disposed • Unequally Disposed - Limit Tolerances

Countersunk Holes

- Used to provide a seating surface for conical screw heads

Counterbore Holes

- Used to recess a bolt or machine screw head below the surface of the part

Chamfered (beveled) edges

- Used to: • Remove burrs after machining operation • Provide for clearances in an assembly (prevent interferences between adjacent components) • Assist in ease assembly of cylindrical features (bolts guided into holes)

Spot-faced Holes

- Very shallow Counterbores • No need to include a depth callout! • Machinist removes sufficient material to achieve the diameter called out on the drawing - Provides a flat surface on a rough stock • Usually used on Castings or non‐flat surfaces (i.e. Cylindrical features) • For the purpose of bearing or seating a bolt head, washer, nut, gasket or fluid fitting

Dimension Lines

- parallel to distance dimensioned, - Arrowheads on both ends, - Broken in the middle for dimension values

Visible Lines (objective lines)

- thick, continuous line representing all of the edges and surfaces of an object that are visible in the view. - Gives the print reader the shape description of the object

Cutting-plane lines

-Short, thick dashed line, terminated with short line at 90 from the cutting plane with arrowheads in the direction of sight for viewing the section. -Each Section View is named with a letter in consecutive order i.e. Section A‐A or B‐B etc.

Extension Lines (witness lines)

-Thin continuous line. -Extends the edges of the object out away from the view

Leaders

-Used to point to a feature or drawing area to which a local note applies. -Used if there is insufficient room for dimensional values. -Always used for diameters of holes & radius of a round

Main 3 Demensions

-height -width -depth

Allowance

= MMC of internal feature - MMC of external feature - If allowance is positive clearance fit - If allowance is negative interference fit (press‐fit)

General Notes

A) General notes: - Placed in horizontal position above or left of the title block - Apply to the entire drawing globally, unless otherwise specified

US Standard

ASME (American Society of Mechanical Engineers Used to be American National Standard Institute (ANSI)

Dimension standards

ASME Y14.5‐2009 Dimensioning and Tolerancing

Dimension Lines

Between the extension lines to indicate the extend and direction of the part dimension. -Broken in the middle for the dimension value and terminated by arrowhead against the extension lines.

CAD stands for

Computer Aided Design

International Standard

International Organization for Standardization(ISO)

prints used for

Manufacturing-Assembly-Communication-Purchasing-QualityControl

Orthographic Projection

Orthographic ProjecƟon ≡ MulƟ‐View Drawings is a system of parallel lines used to project object into projection plane

Five Types of Fits

Running or Sliding Clearance Fit (RC) - Location Clearance Fit (LC) - Transitional Clearance or Interference Fits (LT) - Location Interference Fits (LN) - Force or Shrink Fits (FN) • These abbreviations NOT to be shown on industrial print (it is just away for internal communication)

Cylinder Demensions

The diameter of cylinder should be dimensioned in rectangular view - Not necessarily and not always!

Center Lines

Thin line with alternating long and short dashes. - Used to designate centers of holes, arcs, cylinders, spheres and other symmetrical features. - Used also to indicate paths of motion

Section Lines (hatching)(cross-hatching)

Thin, continuous lines created at an angle. -Indicate the surface of an object in a section view that was "cut" by "cutting plane" - Used both in detail drawings and assembly drawings

drawing

Universal language used by engineers, designers,technicians, and skilled workers to quickly andaccurately communicate necessary information (i.e.size,shape,tolerances,materials,finish,specialtreatmentorinstructions,etc.)tofabricate,assemble and service industrial products.

Leader Lines

Used to point to hole size, threads, or specific feature on the drawing

drawings can be an important part of

a contractual agreement

print is defined as

a copy of a drawing

visualization

ability to envision or "see" the 3D shape of the object from various 2D views shown on a print(paperorscreen).

all lines should be

black

Broken View

dimensions that cross the break lines are broken automatically

print=

drawing

Types of Section View Lines

full section view/half section view/offset section view/aligned section views/broken out section view/revolved section view/removed section view

Oblique Surface:

inclined and rotated with respect to all three planes - Not true shape and size in any projection.

Location Demensions:

indicates the location of the features

Size Dimensions:

indicates the size of the part and the size of its various geometric features

Reference Dimensions

not toleranced, not used in layout, machining, or inspection (quality control)

Normal Surface:

parallel to one plane and perpendicular to the other two planes - True size and shape in only one view - Appears as a line in the other two views

Inclined Surface:

perpendicular to one plane, but inclined to the other two planes - Appear as a line in one view - Appears as foreshortened shape in the other two views

Title Block

provides information that aids in identification and filing of the print, includes: - Name and Address of the company [A] - Drawing number [B] (part or assembly number) - Drawing title [C] (part or assembly name)

interpretation

understanding of lines, symbols, dimensions, notes, instruction and other information on the print.

Visualizing Print Readings:

understanding shape description - Multi‐view drawings - Sectional Views - Symbols screw threads

Interpreting Print Readings:

understanding size description dimensioning - Describes size and location - Choose which dimension to place and where?

a product description describes

what an object should look like when it is completed. As Design Engineers we don't tell manufacturing how to make the part. We just list the final requirements of the part

Break Lines

• "break out" or "break off" a portion of the view. •Short Break Lines •Long Break Lines

American Standard Tolerances

• ASME B4.1‐1967 (R1999) Preferred Limits and Fits for Cylindrical Parts

Baseline Dimensioning

• Also called - Datum dimensioning • Dimensions initiated from a common surface / plane - Known as a "Datum" • Why would we do this?? - Ease of interpretation - Ease of setup for machining and inspection - Doesn't result in tolerance accumulation

Parts List

• Appears immediately above the title block • Also called Bill Of Materials (BOM), List of Materials , materials list

Revision History Block

• As the drawing is revised, the changes must be captured: - Reasons for changes are: • Errors, Design Improvements, Change in Requirements, Customer Request, Producability Changes, etc. • There are two approaches: - On the drawing & in the upper right corner - As a detached Revision Record Document

Section View notes

• Can replace one of the views or be an additional view (auxiliary view). • Can not create a section view from an existing section view!

half section view

• Created for symmetric object, - ½ of the view shown as a section view - ½ of the view shown as a regular view - Notes: - Only one arrowhead - Center line dividing the section » "Not A Visible Line"

full section view

• Cutting plane passes through the entire part • Omit hidden lines, unless needed for complex part to avoid additional views.

Rib Rule

• Defined by the ASME Standard: "Leave web or rib without section lines, when the cutting plane is parallel to the thin material" • Not practiced in industry (We take exception to it!), since most CAD Packages are unable to comply with it very easily. • Acceptable in ME186 to skip the "Rib Rule"

Outline Section View

• For large sectioned area the section lines are drawn along the visible lines • Because fewer line make it easy to read the drawings • Not practiced in industry. Created for pre-CAD days, when a design engineer would use a drafting board to hatch a section

Main 3 Views

• Front View projected on the Frontal plane • Top View projected on the horizontal plane • Right View projected on the profile plane

Main 3 planes in solidworks

• Frontal Plane • Horizontal Plane • Profile Plane

Section Lines

• However, correct pattern may be used to represent the materials, the materials specification should be listed - Title Block - Materials Block - Notes

Part Identification

• Leader to identify parts by "Find Number" from BOM, attached to a Balloon (circular or oval).

Allowance Interference Examples

• Max Interference = 1.2500"‐1.2519"= ‐ 0.0019" • Min Interference = 1.2506" ‐1.2513"= ‐ 0.0007"

Broaching

• Moves a "multiple tooth" cutting tool linearly relative to work in direction of tool -Advantages: Good surface finish Close tolerances Variety of work shapes possible Cutting tool is called a broach

To Over Dimension Or Not to Over Dimensions?

• NEVER • Reference dimensions (x.xxx) - Given to assist in analyzing the design or - Assist machinist to locate features only (not to make it) - Shall not be used to inspect features

Arrow-less Dimensioning

• Ordinate dimensioning • Coordinate dimensioning • Datum dimensioning

Sections in Assembly Drawings

• Orient the section lines in each part at different angles and/or change the spacing • Change the lines slope from right to left in alternating manner • Fasteners and shafts are left uncut (generally!) • Rubber inserts, gaskets, thin plates appears shaded solid

Datum

• Origin from which location of features are established • Reference plane or axis to which geometric control is referenced.

Three Principles

• Principle 1: a flat surface is oriented perpendicular, parallel, or inclined to a plane of projection • Principle 2: All flat surfaces appears in drawing as: - A line, if oriented perpendicular to the plane - True size and shape, if oriented parallel to the plane - Foreshortened, if oriented inclined to the plane

Partial Section View

• Removed section to show details of an object without drawing complete views • It could be drawn at different scale to enlarge the view

Maximum Material Condition (MMC)

• Represent the feature when the most material is present (more material) - For an external feature MMC is the largest value - For an internal feature MMC is the lowest value • Advantage: determine the tightest fit between two parts

Section View Lines

• Section lines: • Shade the area of material cut by cutting-plane. • Different pattern can be used to indicate the type of materials • Usually drawn at 45 but can be drawn at any angle (not // or ⊥ to visible lines)

Two types of demensions

• Size = How big is the feature being described? • Location = Where is the feature being described?

broken-out section view

• Small portion of the part to show the interior construction • The section portion is separated by short break line • Hidden lines may be shown on the "non-section" portion of the view

Removed Section View (details section view)

• The section is out of projection with the other view. • May have different scale to clearly show the details

Basic Size

• The size determined by engineering and design requirements for a part or set of mating parts

Cutting-Plane Lines

• Thick lines, consist of series of medium dashes, or series of two short dashes and one long dashes. • Arrowheads are placed on each end indicating the viewing direction. • Capital letters are placed near the arrowheads.

Third Angle Projection:

• This projection is common throughout the United States • The symbol shown should appear in the title block

First Angle Projection:

• This projection is commonly used in Europe and other countries • The symbol shown should appear in the title block

Holes (thru/blind)

• Thru holes ‐ drill exits opposite side of work • Blind holes - does not exit work opposite side

aligned section view

• Used for cylindrical objects with odd number of features • The cutting-plane line is offset through the features such that they can be rotated to normal vertical or horizontal plane and projected.

Zoning

• Used to aid in locating details of parts or revision notes • Indicated outside of the border

Section Views

• Used to clearly show interior details of an object. • Is created by passing an imaginary cutting plane through the object and removing the part nearest to the observer. • ASME Y14.3 "Multiview and Sectional View Drawings"

Nominal Size

• Used to designate size of commercial product • May or may not express the true numerical size of the part or material.

revolved section view

• Used to show features such as construction cross-sectional area, wheel spoke • The cutting plane slices through the feature parallel to the line of sight, then the cut shape is revolved 90°

Chain Dimensioning

• Used to tie features to each other - Creates a "Relation" between features • Example: A D‐Sub connector cutout on your computer case - Will result in tolerance accumulation (be careful)

offset section view

• When essential details don't appear on one flat plane • The cutting plane line Is drawn offset through the object to include the desired features • Eliminates the need to create multiple section views to capture all internal features

Viewing plane line

• similar to cutting‐plane line but "floats" outside of the object instead of cutting the object.

Phantom Lines

• thin lines composed of long dashes alternating with pairs od short dashes. •Used to indicate alternate position of moving parts.