How do you read a drum brake micrometer?
Place micrometer inside the drum across the greatest diameter to be measured. Hold anvil steady and move dial back and forth against the braking surface to obtain the highest reading. The micrometer is calibrated at the factory. Check the calibration using a No.
How do you measure brake drums?
Always measure the inside of the brake drum before deciding to discard or machine on a lathe. Use a drum micrometer or an equivalent tool to retrieve these measurements. Compare them to the diameter stamped on the outside of the drum. If the drum is scored or grooved, place the tool into the deepest part of the groove.
What is the minimum allowable measurement for scoring of a brake drum?
SCORED DRUMS NOTE: WHEN CHECKING BRAKE DRUM DIAMETER FOR WEAR, THE DIAMETER SHOULD NOT EXCEED . 120″ OVER THE ORIGINAL DIAMETER. WHEN REBORING BRAKE DRUMS, THE FINISHED DIAMETER SHOULD NOT EXCEED . 080″ OVER THE ORIGINAL DIAMETER.
How do you measure brake drums to replace?
Steps for Measuring Brake Drums Properly
- Remove the bolts or retaining clips from drums that hold everything together.
- Use a drum puller to pull off the drum from the wheel.
- Now, search for the maximum diameter in the cast. Most of the time, the diameter is on the rotor on the external surface.
What is measured with a drum micrometer?
A drum micrometer is a single-purpose instrument, used to measure the inside diameter of a brake drum. A drum micrometer has two movable arms on a shaft. One arm has a precision dial indicator ; the other arm has an outside anvil that fits against the inside of the drum.
What is the diameter of a brake drum?
Inner Brake Drum Height: 48,5 mm. Support plate diameter: 59 mm.
What is the maximum brake drum diameter?
Brake drums have a wear limit which is the maximum inside diameter the brake drum is allowed to be. This number is often cast on the outside of the drum it’s allowed to be 422.1 millimeters or sixteen point six two inches. This is for your standard American trailer brake drum or drive axle drum.
What causes brake drums to crack?
Cracked drums can be caused by excessive heating and cooling of the brake drum during operation. You will see a crack extending through the entire wall when inspecting your brake drum if yours is cracked. You should not operate your vehicle at all if you have a cracked drum.
What is the maximum allowable brake drum diameter?
What is the minimum allowable lining thickness?
An air braked commercial motor vehicle shall not be operated with brake lining/pad thickness less than 6.4 mm (1⁄4 inch) or to the wear indicator if the lining is so marked (measured at the shoe center for drum brakes); or less than 3.2 mm (1⁄8 inch) for disc brakes.
Which part of the micrometer has the increments on the bottom?
The micrometer in the illustration has them on the bottom. The thimble of the micrometer has increments of .01 millimeters. Note that there are 50 divisions of .01mm on the thimble of a metric micrometer. The micrometer on the top is set to 6.50 mm.
What size micrometer do you use for reading?
Reading a Micrometer Quiz On all the following questions PAY CLOSE ATTENTION to which micrometer size is being used. 1) Reading #1 Using a 0 to 1 INCH MICROMETER. Shown in the photo is the reading from a 0 – 1 inch micrometer.
What is a metric micrometer and how does it work?
Metric micrometers are similar to standard micrometers. There are markings on the sleeve and the thimble. Notice the sleeve of a metric micrometer has markings on the top and the bottom. There is a handle lock and a ratcheting end to ensure that the same pressure applies to all readings.
What are the markings on the sleeve of a micrometer?
There are markings on the sleeve and the thimble. Notice the sleeve of a metric micrometer has markings on the top and the bottom. There is a handle lock and a ratcheting end to ensure that the same pressure applies to all readings. Whole number increments are on one side of the sleeve, and half-millimeter increments are on the other.