Section 2 Shop Math Review Overview Learning Manufacturing

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Section 2

• Shop Math Review

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OverviewLearning Manufacturing Means Math

• Nearly every action or decision made by
  machinists, is based on numbers.
• And each is often calculated in some way.

A calculator is as common in the modern tool box
as a micrometer!
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Section 2 Goals

• Unit 2-1 Understanding Precision
• gt Say decimals inches using the language of the
  shop
• gt Use measurements at one-thousandth of an inch
  or smaller.
• gt Convert between Metric and Imperial Units.
  (Review)
• Unit 2-2 Self Evaluation
• gt A Pre-Test using typical shop problems. If
  you can do the problems, skip to the Section 2
  Final Review. If not, go to Unit 3 to study the
  solutions then proceed to the Final Review to see
  if your memory has been jogged..
• Unit 2-3 Detailed Answers
• gt Check Your Baseline Math Skills
• gt Decide if you are warm enough or need a bit of
  formal math review
• Final Review Problems
• gt Did the review do enough to warm up the gray
  cells?
• gt A second set just a bit harder than the first

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Unit 2-1 Working With Precision Numbers

• In engineering and machining there are
  conventions weve adopted for working with
  precision numbers and measurements.
• Theyre used by all, because we work with and
  communicate decimal numbers constantly.

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Machinists Lingo for Decimal Numbers

• While we work with inches or millimeters, our
  base units are much smaller.
• For metric units, pronunciation is the same as in
  the rest of the world tenths, hundredths and
  sometimes thousandths of a millimeter.
• But when pronouncing decimal inches, our base
  unit is the thousandth of an inch and we
  pronounce our numbers based on the thousandth
  it has become our adopted base unit.

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For Example

• How would you pronounce this,
• 12.56 inches?
• As odd as it may seem at first, machinists would
  say either
• Twelve inches, five hundred sixty thousandths
• or
• Twelve and five-hundred, sixty thousandth inches

Both would be perfectly understood by fellow
machinists!
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Trade Tip Add zeros when the number doesnt go
to the third column
12.560

• Mentally adding zeros helps to say the number to
  the third decimal place the thousandth column.

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Shop Talk

• Machinists might even shorten the decimal part to
• Five-hundred, sixty thou

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Another Example

• Pronounce this decimal number
• 0.12 inches
• It comes out in machinist lingo
• One-hundred, twenty thousandths

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Dividing Thousandths

• For some extra-precise work, thousandths arent
  fine enough.
• For these situations we divide each thousandth
  into ten smaller parts called Tenths in
  machinist lingo, 0.0001 Inch thats our tenth.
• 0.0001 is called one ten-thousandth in the
  regular math world but not in a machine shop.
• Not tenths of an inch but tenths of our basic
  unit, the thousandth of an inch.

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For Example

• Pronounce this number 3.0998 Inch
• Three inches, ninety-nine and eight tenths
• thousandths
• or
• Three and ninety-nine thousandths inches
• and eight tenths

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Trade Tip

• Pronounce to the third column, then say
• and X tenths

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Advantages to learning the lingo

• Youll learn to read precision tools like these,
  much faster and easier.
• In industry youll sound experienced.
• It promotes exact communication between machinists

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Its also important to get a feel for the size of
precision

• Just how big is a thousandth of an inch?
• A millimeter or hundredth of one?

It helps to relate these units to things
around us
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CD thickness must be closely controlled so that
the read/write beam bounces back perfectly. So
how thick do you estimate them to be?

• .047 in.
• 1.2 mm

Please, dont try this on your student CD!
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A sheet of paper is

• Usually .003 inch
• Shop shortened to
• Three thou
• Just under .01 mm
• One hundredth millimeter
• or its OK to say
• Point zero one millimeters

Trade
Tip .003 in. can be a useful shim for setups and
for measuring!
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How about these common items how thick?

• Nickel
• 0.070 to .080 in.
• 1.78 to 2.0 mm
• Pen
• .32 (three-hundred, twenty thou)
• ?8 mm

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Unit 2-2Math Self Evaluation

• In Unit 2, you will find two sets of problems
  typical of shop work.

• They will help refresh you math skills, getting
  ready for lab assignments
• They will also help determine if a bit of math
  review is in order to be successful in the lab
  and trade.
• The best hint is (as always) read the
  instructions and hints before starting!

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Heres two tips to help

• First, if some of the terms are unfamiliar, look
  them up in the text. They arent part of the
  test.
• Second, be aware of a few built in traps in shop
  type problems we call them predictable error
  points (PEPS)

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A Typical PEP
When spaces or divisions occur, be cautious of
how many there are!
Remember this small trap, it may come up in the
problems!
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Good Calculating on those problems!
Conclusion
Not to worry, if you havent been very successful
in math in the past. Shop math is easy to learn
because its relevant, all the facts are right
there on the drawing which leads us to Section
3 getting those facts from the drawing.