Math-in-CTE Lesson Plan Template
Lesson Title: Brake rotor measurement / Lesson # 8Author(s): / Phone Number(s): / E-mail Address(es):
Dale Winchell / 703-228-5749 /
Martha Byron / 571-239-8440 /
Occupational Area: Auto Tech- Brakes
CTE Concept(s): Brake rotor measurement
Math Concepts: Measurement with micrometer
Place value of decimals and vocabulary of basic units
Adding decimals
Lesson Objective: / Be able to perform brake rotor thickness measurements.
Be able to interpret results to determine if rotor is within specifications
Supplies Needed: / Micrometers, six items to measure in classroom, brake rotors, shop vehicle, smart board.
Copies of place value chart , pencils, deep throat micrometer.
The "7 Elements" / Teacher Notes
(and answer key)
1. Introduce the CTE lesson.
Question: How many of you have ever been in a car that rides smooth driving down the road, but when the brakes are applied the whole car shakes or the steering wheel shakes?
Have you ever thought to yourself, what could be causing this to happen?
Well I am going to show you how to diagnose this kind of problem.
There are two causes for this kind of problem.
1. Brake rotor thickness variation
2. Brake rotor run out.
Brake rotor thickness variation is where the brake rotor has become thin in one or two spots around the circumference of the rotor.
Brake rotor run out is the wobble in the rotor as it rotates on its axis.
Show illustration of Rotor run out and explain what happens.
One cause for these rotor problems is that the rotor has become too thin from wear and the rotor overheats. When the rotor overheats it warps, causing excessive run out or wobble.
What I am going to show you is how to perform rotor measurements using a micrometer to determine if the brake rotors are too thin.
In order to make measurements with a micrometer and interpret the results you need to understand how to read a micrometer and understand some things about decimals.
2. Assess students’ math awareness as it relates to the CTE lesson.
Has anyone ever used a micrometer?
Has anyone ever heard of a deep throat micrometer? Show them one and point out the differences such as deeper frame and pointed anvil to get into a groove in the rotor.
I have a little activity I want you to complete to see what you know about reading a micrometer.
Pass out place value sheets. Have students fill in the numbers from the board on their sheets.
Put up place value chart on smart board.
When students are finished filling in their numbers on their sheets, call on them to fill in one number on the board chart and have the students read the number aloud. Collect papers.
/ 0.500
1.250
125
0.0005
1.0015
Five ten thousandths
Seven hundred fifty thousandths
One inch and one hundred twenty five thousandths
One thousand
One thousandth or one one thousandth
3. Work through the math example embedded in the CTE lesson.
Hand out micrometers and show picture of micrometer parts on smart board. This is an outside micrometer. It can measure to one ten thousandth of an inch. Please be careful with it, if you drop it you will damage it. Explain what the parts are called. Put up picture of micrometer on smart board and explain how to use the micrometer to make measurements. To read a micrometer, follow these four steps:
1. Note the largest number on the sleeve. Each number equals .100
2. Count the number of graduated lines to the right of the sleeve number. Each full sleeve graduation equals .025 (two lines equal .050)
3. Note the thimble graduation aligned with the horizontal sleeve line. Each thimble graduation equals .001 (round off when the sleeve line is not directly aligned with a thimble graduation.
4. Add the decimal values from steps 1,2, and 3. Make sure to line up the decimal point when adding. The sum is the micrometer reading in inches. Using your micrometer, measure the six items given and write down your measurements. Help students come up with the numbers to add up that were taken from the micrometer. Add the numbers together to get readings.
Group students to share micrometers and work together.
Have students practice measuring six items and write their measurements down in the order that they read them from the micrometer. There are three values that need to be added together to get the sum measurement. Show teacher results.
/ Use example of a micrometer reading on smart board to walk them through each step.
Pre measure the six items listed below:
Paper clip
Textbook cover
Wooden pencil
Whiteboard marker
Student desk top
Nut or washer
4. Work through related, contextual math-in-CTE examples.
Give instructions to measure for rotor thickness variation by taking measurements from six different places around the circumference of the rotors at the marks made on the rotors.
Practice measuring the rotors on the bench, and write down the three values from each of the six measuring marks. Show results to teacher.
Work in same groups. / Pre-measure rotors and mark them Rotor A, Rotor B, etc. Make six evenly spaced marks on each rotor to indicate where they are to measure for thickness variation.
5. Work through traditional math examples.
Using the three values from each of your six rotor measurements, practice lining up decimals and adding the three numbers together to get the final rotor measurements. Then find the largest number(measurement) and the smallest number(measurement) between your six measurements and subtract the smaller number from the larger number to determine the difference between the two. This difference is called thickness variation and can be compared with the specification. Generally less than .0005 or Five tenthousandths of an inch. / Specs. can be found in Alldata Online service info. Database.
6. Students demonstrate their understanding.
Measure rotors on a shop vehicle and compare readings to the minimum thickness specification in the service information. Determine if the rotor can be reused on the car, or has to be replaced. / Specs. can be found in Alldata Online service info. database.
7. Formal assessment.
Final exam on brakes including the following questions.
1. A 1998 Chevrolet Cavalier’s steering wheel shakes when the brakes are applied. What is the most likely cause?
2. A brake rotor is measured at .315 and the specification for brake rotor discard thickness is .322, can this rotor be reused?
3. You are replacing the front brakes on 2001 Honda Civic. You notice that the brakes were pulsating when you drove the car in the shop. You measure the rotors at .789 and the minimum thickness specification after machining is .760, what do you do? / 1. Rotors are out of true.
2. No, it is thinner than specification.
3. Reface the rotor and re measure it to make sure it is still within spec.
NOTES: