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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Shop safety (p. 19)Shop safety Shop math (p. 23) Introduction to blueprint reading (p. 39) Tolerance interpretation (p. 44) Measuring devices (p. 50) Lesson Topics Shop math practice Shop math quiz Blueprint reading quiz Tolerance interpretation review and practice Tolerance interpretation quiz Drawing for exercise 1 Special note: Any one of these topics could fill an entire course by itself. We only scratch the surface of each topic. Our intention is simply to provide enough information about basic machining practices so that students can understand upcoming presentations. More things to do for this lesson:

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 A machine shop is a dangerous place! We cannot prepare you for every dangerous situation You must always be alert Safety equipment Protective eyewear Clothing Hearing protection Safety shoes Helmets Gloves Respirators and facemasks First aid kits Fire extinguishers Cranes and hoists Warning signs Shop safety Safety practices When in doubt, ask! Raw material handling Heavy, sharp, greasy, slippery, dirty, sharp edges, chip residue, awkward shape Finished workpiece handling In addition to raw material handling: Hot Spring Tightening and loosening fasteners Getting around in the shop Behave in a professional manner No horseplay! Machining-center-specific safety issues Safety interlocks, guarding, signs, safe operating procedures Next topic: Shop math

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Calculator recommendations Keep it simple Watch out for trick functions Avoid solar powered calculators Big buttons-big display Clear entry button Next topic: Blueprint reading Shop math

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Arithmetic operations Most CNC operator work can be done with the four basic arithmetic operators: Add (+): Subtract (-): Multiply (X or *): Divide (/): = = 3 2 * 9 = / 2 = 10 Entries into CNC machines are done in decimal format (fractions are never used) 1/8 = /16 = You may be able to do some calculations in your head 20 / 2 = ? (20 divided by 2) = ? = ? = ? = ? But don’t hesitate to use your calculator if you’re in doubt = ? Shop math Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Arithmetic expressions An expression is a math question to be answered… = 7 Question Answer – 2 = ? 7 – = ? 10 * 2 / 5 = ? (10 times 2 divided by 5) Shop math Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Priority of arithmetic operations Consider this expression: / 4 = ? What answer did you come up with? divided by 4 is 4, right? But wait a minute – there is another way to do this… / 4 = ? 3 4 plus 3 is 7 Which answer is correct? Shop math Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Priority of arithmetic operations With no other math “punctuation”…… division has a higher priority than addition / 4 = ? 3 4 plus 3 is 7 The correct answer is 7 Shop math Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Priority of arithmetic operations Parentheses can be used to specify operation order ( ) (4 + 12) / 4 = ? This makes it clear that 4 must be added to 12 first. Then the result (16) is divided by 4. The answer is 4. Order of arithmetic priorities: 1)Anything in parentheses 2)Functions (like square root, sine, cosine, tangent) 3)Multiplication 4)Division 5)Addition 6)Subtraction 3 * (4 + 2) = ? / 2 = ? (8 + 2) / 5 = ? / 2 = ? / = ? 8 * (2 + 3) / 2 = ? Shop math Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Using a formula A formula is an arithmetic expression that contains variables rpm = 3.82 * sfm / tool diameter rpm represents spindle revolutions-per-minute sfm represents speed in surface- feet-per-minute tool diameter represents the diameter of the cutting tool With this formula, consider this situation: You need to drill a 0.5 in diameter hole and the cutting tool manufacturer recommends 80 surface feet per minute. rpm = 3.82 * 80 / 0.5 What rpm will you use? Shop math Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Measurement systems Some companies in the United States use the Imperial system Other companies use the Metric system (the Metric system is used almost exclusively in other countries) The inch is the most basic unit of distance in the machine shop The millimeter is the most basic unit of distance in the machine shop How big is an inch? A deck of playing cards is about ½ an inch How big is a millimeter? The thickness of a quarter- dollar is about one millimeter One inch = 25.4 millimetersOne millimeter = inches (about one-twenty-fifth of an inch) Shop math Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Measurement systems To convert millimeters to inches: To convert inches to millimeters: inches = millimeters / 25.4millimeters = inches * 25.4 How many inches is 350 millimeters?How many millimeters is 3.5 inches? Shop math Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Decimal places A whole number is called an integer Consider this real number: 4, 5, 8, 44, 103, 3,373, and 26,252 are examples of integers is an example of a real number Shop math A number containing a portion of a whole number is called a real number In a real number, the values to the right of the decimal point are called decimal places There are three decimal places to the right of the decimal point With most CNC machines… Metric system allows up to three decimal places Imperial system allows up to four decimal places Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Fractional format When using the Imperial measurement system (not the Metric system)… Consider this fraction: But a CNC machine cannot accept fractional format Fractions must be converted to decimal format Shop math Some values may be specified with fractions To convert a fraction to decimal format, divide the numerator (top or left number) by the denominator (bottom or right number) 13/16 Pronounced as “thirteen-sixteenths” Divide 13 by (the result) is the decimal format of 13/16 Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Saying numbers out loud in a machine shop In the Imperial measurement system: 1.0 : “one inch” 0.1 : “one-hundred-thousandths of an inch” 0.01 : “ten-thousandths of an inch” : “one-thousandth of an inch” : “one tenth” (even though this value is really one ten-thousandth of an inch) Shop math More examples: : “forty-seven thousandths” : “two-hundred-fifty thousandths” : “six-hundred-eighty-four thousandths” : “one inch, four-hundred-fifty-five thousandths” : “four inches, three-hundred-seventy-two thousandths, and three tenths” Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Saying numbers out loud in a machine shop In the Metric measurement system: 1.0 : “one millimeter” 0.1 : “one-hundred microns” 0.01 : “ten microns” : “one micron” Shop math More examples: : “forty-seven microns” : “two-hundred-fifty microns” : “six-hundred-eighty-four microns” : “one millimeter, four-hundred-fifty-five microns” Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Polarity All values have a polarity (plus or minus) Shop math With CNC machines, plus is always assumed If no polarity sign is specified (+ or -), the value is assumed to be positive All values shown to this point have been positive To specify a negative value, the minus sign (-) is used: (negative three thousandths of an inch) When you subtract a number from a smaller number, the result will be negative = Next topic: Blueprint reading

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HomeLesson topics CNC Turning Center Setup and Operation Lesson 1: Basic machining practices required for turning centers Copyright 2010 Summary Most calculations required of setup people and operators are pretty simple Shop math The trick lies in doing simple calculations – over and over again – with out making any mistakes! Next topic: Blueprint reading Mistakes will, of course, result in scrap parts – or worse

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