Machining and CNC Technology Section 2 Shop Math Review Machining and CNC Technology

Overview Learning 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! Machining and CNC Technology

Machining and CNC Technology Section 2 Goals Unit 2-1 Understanding Precision > Say decimals inches using the language of the shop > Use measurements at one-thousandth of an inch or smaller. > Convert between Metric and Imperial Units. (Review) Unit 2-2 Self Evaluation > 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 > Check Your Baseline Math Skills > Decide if you are warm enough or need a bit of formal math review Final Review Problems > Did the review do enough to warm up the gray cells? > A second set just a bit harder than the first Machining and CNC Technology

Unit 2-1 Working With Precision Numbers In engineering and machining there are conventions we’ve adopted for working with precision numbers and measurements. They’re used by all, because we work with and communicate decimal numbers constantly. Machining and CNC Technology

Machinist’s 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. Machining and CNC Technology

Machining and CNC Technology 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! Machining and CNC Technology

Machining and CNC Technology Trade Tip Add zeros when the number doesn’t go to the third column 12.560 Mentally adding zeros helps to say the number to the third decimal place – the thousandth column. Machining and CNC Technology

Machining and CNC Technology Shop Talk Machinists might even shorten the decimal part to “Five-hundred, sixty thou” Machining and CNC Technology

Another Example 0.12 inches “One-hundred, twenty thousandths” Pronounce this decimal number: 0.12 inches It comes out in machinist lingo “One-hundred, twenty thousandths” Machining and CNC Technology

Machining and CNC Technology Dividing Thousandths For some extra-precise work, thousandths aren’t fine enough. For these situations we divide each thousandth into ten smaller parts – called “Tenths” in machinist lingo, 0.0001 Inch that’s 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. Machining and CNC Technology

Machining and CNC Technology 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 Machining and CNC Technology

Pronounce to the third column, then say “and X tenths” Trade Tip Pronounce to the third column, then say “and X tenths” Machining and CNC Technology

Advantages to learning the lingo You’ll learn to read precision tools like these, much faster and easier. In industry you’ll sound experienced. It promotes exact communication between machinists Machining and CNC Technology

It’s 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 Machining and CNC Technology

Machining and CNC Technology 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, don’t try this on your student CD! Machining and CNC Technology

Machining and CNC Technology A sheet of paper is Usually .003 inch Shop shortened to “Three thou” Just under .01 mm “One hundredth millimeter” or it’s OK to say “Point zero one millimeters” Trade Tip .003 in. can be a useful shim for setups and for measuring! Machining and CNC Technology

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 Machining and CNC Technology

Unit 2-2 Math 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! Machining and CNC Technology

Here’s two tips to help: First, if some of the terms are unfamiliar, look them up in the text. They aren’t part of the test. Second, be aware of a few built in traps in shop type problems – we call them predictable error points (PEPS) Machining and CNC Technology

Machining and CNC Technology 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! Machining and CNC Technology

Good Calculating on those problems! Conclusion Not to worry, if you haven’t been very successful in math in the past. Shop math is easy to learn because it’s relevant, all the facts are right there on the drawing – which leads us to Section 3 – getting those facts from the drawing. Machining and CNC Technology