Telecurso 2000 - Metrologia - 14 Verificadores

Understanding Indirect Measurement in Mechanics

Introduction to Indirect Measurement

• Jorge introduces the concept of indirect measurement using a ring template for measuring finger sizes, which is also applicable in mechanics.

• The previous teleclass focused on calibrators, while today's session will cover verifiers and their functions.

Types of Control Rulers

• Control rulers are essential tools for checking flat surfaces and can be made from steel or cast iron. They are categorized into two groups: rectified wire rulers and rectified or raked face rulers.

• The beveled ruler, made of carbon steel with a rounded edge, is used to check flat surfaces by observing light passing through when placed against the surface.

Using Rulers for Quality Checks

• For pieces with square holes where a beveled ruler cannot be used, a triangle ruler is recommended due to its design that accommodates various shapes.

• Both ground and raked face rulers help identify high points on flat surfaces that need scraping; the triangular ruler checks alignment at acute angles or warping in engine blocks.

Maintenance of Measuring Instruments

• Proper care involves avoiding pressure on the ground wire ruler during use and ensuring it does not come into contact with other instruments to prevent damage. Regular cleaning and lubrication after use are crucial for longevity.

• Rust should be removed carefully using stone, pumice, and oil; sandpaper is not advisable as it can cause further damage to the instrument's surface.

The Importance of Precision Squares

Functionality of Precision Squares

• Precision squares are vital for verifying 90º angles in mechanical work; they come in various types based on shape and size, including simple one-piece squares and those designed for tracing pieces effectively.

• The dimensions of squares (blade length L1 and base length L2) vary significantly, necessitating specific tables to standardize measurements according to ABNT standards.

Templates as Measuring Instruments

Understanding Verification Instruments in Mechanics

Overview of Templates and Jigs

• Templates are essential tools for performing checks, controls, and facilitating operations in mechanical work. They can be simple instruments made from carbon steel and may even be self-manufactured by mechanics.

• The shapes, types, and sizes of templates vary based on the specific tasks they are designed for. Commercial templates come in standardized forms such as radius checkers and fixed angle checkers.

Types of Checking Instruments

• A lightning checker is introduced as a tool to measure internal and external radii, with each blade stamped with its corresponding radius measurement (1 to 15 mm or 1/32 inches to ½ inch).

• The difference between concave and convex radius checking is explained; one side checks concave while the other checks convex radii. An angle checker is also mentioned for measuring surfaces at various angles (1º to 45º).

Measuring Thicknesses with Dies

• To determine the thickness of sheets used in part manufacturing, dies (or sheet/wire checkers) are utilized. These tools have notches that correspond to different wire diameters or sheet thicknesses.

• The process involves trial and error to find a groove that fits the material being checked. Specific tables help compare measurements adopted from England and the United States.

Threading Tools and Their Checks

• Templates for metric threads are necessary for checking threading tools on lathes. A thread checker measures threads per inch or pitch in millimeters through engraved markings on its blades.

• A drill angle checker is used to assess drill bit sharpness by measuring a specific angle (59º), ensuring proper maintenance of workshop tools.

Final Thoughts on Instrumentation

• The feeler gauge is highlighted as an instrument for checking lathe dovetail clearance; it consists of calibrated blades that can be replaced.

• The session concludes with a review emphasizing how understanding these verification instruments can enhance productivity without compromising quality, encouraging further study through provided exercises.