Telecurso 2000 - Metrologia - 06 Leitura no Sistema Inglês

Summary

This video lesson explains how to use a caliper to take precise measurements in the imperial system, focusing on inches and their fractions. It covers both reading decimal inches (milesimal) and fractional inches, using examples to illustrate the process. The tutorial emphasizes the importance of understanding both the main scale and the micrometer scale (nonius) of the caliper, and provides a step-by-step guide to performing measurements. Tips for quickly reading fractional inches are included, along with practice exercises for mastering the technique. By the end of the video, users are equipped with practical skills for accurate measurement in inches.

Takeaways

• 😀 Understanding how to read a caliper in the English system is important for professionals in the field of measurement.
• 😀 The most commonly used unit in the caliper is millimeters, but knowledge of inches and fractions of an inch is equally essential.
• 😀 In the English system, a caliper with a thousandth-inch scale divides each inch into 40 parts, each part representing 1/40th of an inch, or 25 thousandths of an inch.
• 😀 The resolution of a caliper in thousandths of an inch is calculated by dividing the smallest unit on the fixed scale by the number of divisions on the nonius.
• 😀 For example, a caliper with 25 divisions on the nonius and 25 thousandths of an inch on the fixed scale results in a resolution of 1 thousandth of an inch.
• 😀 The reading procedure for the English system is similar to that of the metric system, but requires counting fractions of an inch on both the fixed scale and the nonius.
• 😀 To read a measurement, count the number of thousandths of an inch to the left of zero on the nonius and add the matching value from the fixed scale.
• 😀 A caliper can also be used to measure fractional inches, where each division corresponds to a fraction of an inch (e.g., 1/8th, 1/16th, etc.).
• 😀 In fractional inch readings, calculations require selecting the correct fraction based on the denominators of the fractions on both the fixed scale and the nonius.
• 😀 A simple rule for fractional inch measurements: select a fraction from the fixed scale with the same denominator as the nonius, multiply the number of divisions by the numerator, and add the result to the nonius reading for the final measurement.

Q & A

What is the key focus of the video script?

The video focuses on teaching how to read a caliper in the English measurement system, specifically in inches, and how to interpret measurements in both decimal and fractional inches.

How is the resolution of the micrometer in the English system calculated?

The resolution of the micrometer is calculated by dividing the smallest division on the fixed scale by the number of divisions on the Vernier scale. In the case of the milesimal caliper, the smallest division is 25 thousandths of an inch, and the Vernier scale has 25 divisions, resulting in a resolution of 1 thousandth of an inch.

What is the procedure to read the measurement on a caliper in inches?

To read a caliper in inches, count the number of divisions on the fixed scale before the zero of the Vernier scale. Then, look for the division on the Vernier scale that coincides with a line on the fixed scale. Add the two values together to obtain the final measurement in inches.

How are fractional inches measured using a Vernier caliper?

For fractional inches, the fixed scale is graduated in inches and their fractions. The Vernier scale helps refine the measurement by adding further fractions of an inch. The total reading is found by adding the reading from the fixed scale and the fractional measurement from the Vernier scale.

What is the significance of the fractions used in the English system of measurement?

Fractions in the English system are essential for more precise measurements, especially in fields like metalworking. The caliper helps to read these fractions, such as 1/128 or 3/16 of an inch, by aligning the Vernier scale to a corresponding division on the fixed scale.

What common mistake should be avoided when reading a caliper in the English system?

A common mistake is failing to correctly add the fractions from the Vernier scale and the fixed scale. It's important to ensure that the correct fraction is identified and added accurately to avoid measurement errors.

What is the role of the Vernier scale in measuring fractional inches?

The Vernier scale plays a crucial role in providing finer measurements for fractional inches. It refines the reading on the fixed scale, allowing for the measurement of small increments such as 1/128 or 3/64 of an inch.

How do you perform the calculation for fractional inches using the Vernier scale?

To calculate fractional inches, you first identify the fraction on the fixed scale, then look at the Vernier scale for the corresponding fraction. Multiply the number of divisions on the fixed scale by the numerator of the fraction and add it to the Vernier scale's reading.

Why is it important to understand the English system when working with calipers?

Understanding the English system is important because many industries, particularly in mechanical and metalworking fields, still use inches and fractional inches for precise measurements. Knowledge of both systems allows professionals to interpret measurements correctly and avoid errors.

What does the term 'milesimal' refer to in this context?

The term 'milesimal' refers to measurements in thousandths of an inch. A milesimal caliper allows for the precise measurement of increments as small as 1 thousandth of an inch, providing a higher level of detail compared to regular calipers.