ix End-of-Unit Content End-of-unit material provides an opportunity for review and application of concepts. A concise Summary provides an additional review tool and reinforces key learning objectives. This helps you focus on important concepts presented in the text. Know and Understand questions enable students to demonstrate knowledge, identification, and comprehension of unit material. Critical Thinking questions develop higher-order thinking and problem solving, personal, and workplace skills. Apply and Analyze questions extend learning and help you analyze and apply knowledge. 108 Machine Trades Print Reading Copyright Goodheart-Willcox Co., Inc. ■Reference dimensions are dimensions without tolerances that only give basic measurement information. A reference dimension is placed between parentheses. ■ A tolerance is an allowable variance of a dimension for a part or feature. It controls the size, form, orientation, location, shape, function, and movement of a part or any of its features. ■Direct tolerancing refers to applying tolerances directly to dimensions or features. Limit dimensioning and plus and minus tolerancing are direct tolerancing methods used to apply tolerances to dimensions for features of size. ■Limits are the maximum and minimum sizes allowed for a dimension. The high limit is the maximum value given to a dimension, and the low limit is the minimum value given to a dimension. The difference between the high limit and the low limit is the tolerance. ■ A single limit dimension is a variance on a dimension that refers to either an absolute maximum value or an absolute minimum value. Single limits are only used when other geometry in the design controls the unspecified limit. ■ Plus and minus tolerancing is a method of tolerancing that specifies a dimension’s variation in a positive and negative direction. The plus symbol (+) indicates a tolerance in the positive direction and the minus symbol (–) indicates a tolerance in the negative direction. ■A unilateral tolerance is a variance from a dimension in only one direction. A bilateral tolerance is a variance from a dimension in both directions. ■A specified tolerance is any tolerance directly applied to a dimension. ■An unspecified tolerance is a tolerance that applies to a dimension that does not have a specified tolerance. Unspecified tolerances appear in a general note. SUMMARY ■A dimension is a measurement of definite value of the distance between two given points on an object. It describes the size and shape of a part and the location of its features. ■Decimal inch dimensions are measurements based on decimal inches. A decimal inch is the decimal equivalent of a fraction of an inch. ■Fractional dimensions are measurements based on fractional numbers. Common fractional values on a drawing are 64ths, 32nds, 8ths, 4ths, and halves. ■Metric dimensions are measurements based on metric units. The millimeter is the most common metric unit of linear measurement used on engineering drawings. ■Angular dimensioning is a system of dimensioning angles that measures the angle of a line or surface from a given reference point. The degree is the unit of measurement for angles and is based on 360 divisions of a circle’s circumference. ■A degree can be broken down into minutes and seconds. There are 60 minutes in one degree and 60 seconds in one minute. ■Dual dimensioning is a dimensioning system in which both US Customary and metric units are used for dimensions. The dominant system appears first, followed by the alternate system. ■Tabular dimensioning is a dimensioning system that uses letters or numbers referenced to a table instead of dimension lines. It is a common method for dimensioning parts that are produced multiple times and have the same shape but different sizes. ■Rectangular coordinate dimensioning without dimension lines is a dimensioning system that specifies coordinate values in reference to an origin. The origin is established by two or three intersecting reference planes. ■ Polar coordinate dimensioning is a dimensioning system that locates a point, line, or surface with a linear distance and an angular measurement from a fixed point of two intersecting perpendicular planes. It is commonly used to locate features on circular parts. Ch07.indd 108 4/23/2020 10:11:34 AM Unit 1 Drawings and Prints 7 Copyright Goodheart-Willcox Co., Inc. Name ______________________________________________ Date ________________ Class _________________ Unit Review KNOW AND UNDERSTAND Answer the following questions using the information provided in this unit. ______ 1. The two primary phases of the manufacturing process are the _____ phase and the production phase. A. drawing B. design C. prototyping D. assembly ______ 2. On a design team, a(n) _____ is responsible for creating the design documents and ensuring the product meets the design criteria. A. engineer B. inspector C. machinist D. accountant ______ 3. Which of the following is a potential use for a 3D part model? A. 2D drawings B. Computer simulation and analysis C. Creating a prototype D. All of the above. ______ 4. True or False? Manual drafting skills have no value in today’s manufacturing industry. ______ 5. _____ drawings provide all the information needed to manufacture an individual part. A. Assembly B. Prototype C. Detail D. Manual ______ 6. True or False? Print reading skills are not valuable to a QC inspector. CRITICAL THINKING 7. Compare additive manufacturing and subtractive manufacturing and name an example of each. __________________________________________________________________________________________________________ __________________________________________________________________________________________________________ __________________________________________________________________________________________________________ __________________________________________________________________________________________________________ __________________________________________________________________________________________________________ 8. Name a manufacturing occupation that interests you and explain how print reading skills are used by the occupation. __________________________________________________________________________________________________________ __________________________________________________________________________________________________________ __________________________________________________________________________________________________________ __________________________________________________________________________________________________________ __________________________________________________________________________________________________________ Ch01.indd 7 4/23/2020 10:38:12 AM 110 Machine Trades Print Reading Copyright Goodheart-Willcox Co., Inc. Name ______________________________________________ Date ________________ Class _________________ Apply and Analyze ACTIVITY 7-1 Snap Ring Refer to Activity Print 7‑1. Study the drawing and familiarize yourself with the dimensions, title block, and notes. Read the questions, refer to the print, and write your answers in the blanks provided. 1. What is the part number? 2. Name the type of material used to make the part. 3. State what change was made by revision D. 4. What is the scale of the drawing? 5. Who released revision A for production? 6. What size is the drawing? 7. Who created the drawing? 8. What is the ring thickness? 9. What is the required width of the blue paint stripe? 10. What tolerance is specified for angles? 11. Who was responsible for making revision B? 12. What is the name of the part? 13. Dimensions .280, 3.835, .134, and .334 are examples of what type of limits? 14. What tolerance is used for one-place decimal dimensions? 15. What is the minimum allowable size on the .136 diameter dimension? 16. What is the tolerance for the ring thickness? 17. The ring should be made from what existing part? 18. What is the tolerance for the ring width opposite the gap? 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. Ch07.indd 110 4/23/2020 10:11:35 AM Unit 7 Dimensions and Tolerances 111 Copyright Goodheart-Willcox Co., Inc. Goodheart-Willcox Publisher Activity Print 7-1. Snap Ring. Ch07.indd 111 4/23/2020 10:11:35 AM