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Shop safety (p. 19) Shop math (p. 23) Introduction to blueprint reading (p. 39)

Lesson Topics. Shop safety (p. 19) Shop math (p. 23) Introduction to blueprint reading (p. 39) Tolerance interpretation (p. 44) Measuring devices (p. 50).

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Shop safety (p. 19) Shop math (p. 23) Introduction to blueprint reading (p. 39)

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  1. Lesson Topics • Shop safety (p. 19) • Shop math (p. 23) • Introduction to blueprint reading (p. 39) • Tolerance interpretation (p. 44) • Measuring devices (p. 50) 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: Shop math practice Shop math quiz Blueprint reading quiz Tolerance interpretation review and practice Tolerance interpretation quiz Drawing for exercise 1

  2. Shop safety • 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 • 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

  3. Shop math • 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

  4. Most CNC operator work can be done with the four basic arithmetic operators: Add (+): Subtract (-): Multiply (X or *): Divide (/): 3 + 4 = 7 7 - 4 = 3 2 * 9 = 18 20 / 2 = 10 Entries into CNC machines are done in decimal format (fractions are never used) 1/8 = 0.125 3/16 = 0.1875 But don’t hesitate to use your calculator if you’re in doubt 125.352 - 13.837 = ? Shop math • Arithmetic operations You may be able to do some calculations in your head 20 / 2 = ? (20 divided by 2) 2.5 + 0.5 = ? 3.0 - 0.25 = ? 5.25 + 8.75 = ? 109.75 - 3.5 = ? Next topic: Blueprint reading

  5. Answer Question Shop math • Arithmetic expressions An expression is a math question to be answered… 3 + 4 = 7 4 + 6 – 2 = ? 7 – 3 + 5 = ? 10 * 2 / 5 = ? (10 times 2 divided by 5) Next topic: Blueprint reading

  6. 16 3 Shop math • Priority of arithmetic operations Consider this expression: 4 + 12 / 4 = ? 4 + 12 / 4 = ? What answer did you come up with? 4 plus 3 is 7 16 divided by 4 is 4, right? Which answer is correct? But wait a minute – there is another way to do this… Next topic: Blueprint reading

  7. 3 Shop math • Priority of arithmetic operations With no other math “punctuation”… … division has a higher priority than addition 4 + 12 / 4 = ? 4 plus 3 is 7 The correct answer is 7 Next topic: Blueprint reading

  8. Shop math • Priority of arithmetic operations Order of arithmetic priorities: Parentheses can be used to specify operation order • Anything in parentheses • Functions (like square root, sine, cosine, tangent) • Multiplication • Division • Addition • Subtraction ( ) (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. 3 * (4 + 2) = ? 5 + 0.5 / 2 = ? (8 + 2) / 5 = ? 7 + 9 / 2 = ? 4 + 1 / 2 - 2 = ? 8 * (2 + 3) / 2 = ? Next topic: Blueprint reading

  9. Shop math • Using a formula With this formula, consider this situation: A formula is an arithmetic expression that contains variables You need to drill a 0.5 in diameter hole and the cutting tool manufacturer recommends 80 surface feet per minute. rpm = 3.82 * sfm / tool diameter rpm = 3.82 * 80 / 0.5 • rpm represents spindle revolutions-per-minute • sfm represents speed in surface-feet-per-minute • tool diameter represents the diameter of the cutting tool What rpm will you use? Next topic: Blueprint reading

  10. How big is an inch? How big is a millimeter? A deck of playing cards is about ½ an inch The thickness of a quarter-dollar is about one millimeter Shop math • Measurement systems Other companies use the Metric system (the Metric system is used almost exclusively in other countries) Some companies in the United States use the Imperial system 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 One inch = 25.4 millimeters One millimeter = 0.0397 inches (about one-twenty-fifth of an inch) Next topic: Blueprint reading

  11. Shop math • Measurement systems To convert inches to millimeters: To convert millimeters to inches: inches = millimeters / 25.4 millimeters = inches * 25.4 How many inches is 350 millimeters? How many millimeters is 3.5 inches? Next topic: Blueprint reading

  12. There are three decimal places to the right of the decimal point Shop math • Decimal places Consider this real number: A whole number is called an integer 5.436 A number containing a portion of a whole number is called a real number 4, 5, 8, 44, 103, 3,373, and 26,252 are examples of integers 3.274 is an example of a real number With most CNC machines… Metric system allows up to three decimal places In a real number, the values to the right of the decimal point are called decimal places Imperial system allows up to four decimal places Next topic: Blueprint reading

  13. 13/16 Pronounced as “thirteen-sixteenths” Shop math • Fractional format Consider this fraction: When using the Imperial measurement system (not the Metric system)… Some values may be specified with fractions But a CNC machine cannot accept fractional format Divide 13 by 16 0.8125 (the result) is the decimal format of 13/16 Fractions must be converted to decimal format To convert a fraction to decimal format, divide the numerator (top or left number) by the denominator (bottom or right number) Next topic: Blueprint reading

  14. Shop math • 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” 0.001 : “one-thousandth of an inch” 0.0001 : “one tenth” (even though this value is really one ten-thousandth of an inch) More examples: 0.047 : “forty-seven thousandths” 0.250 : “two-hundred-fifty thousandths” 0.684 : “six-hundred-eighty-four thousandths” 1.455 : “one inch, four-hundred-fifty-five thousandths” 4.3723 : “four inches, three-hundred-seventy-two thousandths, and three tenths” Next topic: Blueprint reading

  15. Shop math • 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” 0.001 : “one micron” More examples: 0.047 : “forty-seven microns” 0.250 : “two-hundred-fifty microns” 0.684 : “six-hundred-eighty-four microns” 1.455 : “one millimeter, four-hundred-fifty-five microns” Next topic: Blueprint reading

  16. Shop math • Polarity All values have a polarity (plus or minus) 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: -0.003 (negative three thousandths of an inch) When you subtract a number from a smaller number, the result will be negative 5.002 - 5.006 = -0.004 Next topic: Blueprint reading

  17. Shop math • Summary Most calculations required of setup people and operators are pretty simple The trick lies in doing simple calculations – over and over again – with out making any mistakes! Mistakes will, of course, result in scrap parts – or worse Next topic: Blueprint reading

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