Selection of Measuring Tools
Before each measurement, it is necessary to select the measuring tool based on the specific characteristics of the part being measured. For instance, for dimensions such as length, width, height, depth, outer diameter, and step differences, calipers, height gauges, micrometers, and depth gauges can be chosen; for shaft diameters, micrometers and calipers can be selected; for holes and slots, plug gauges, block gauges, and feeler gauges can be used; for measuring the straight angles of parts, a square ruler can be used; for measuring R values, an R gauge can be used; for parts with tight fit tolerances, high precision requirements, or when calculating geometric tolerances, a 3D or 2D coordinate measuring machine can be used; for measuring the hardness of steel, a hardness tester can be used.
Application of Calipers
Calipers can measure the inner diameter, outer diameter, length, width, thickness, step difference, height, and depth of an object. They are the most commonly used and convenient measuring tools, with the highest frequency of use in the processing site.
Digital Calipers: With a resolution of 0.01mm, they are used for measuring dimensions with tight fit tolerances (high precision). Before using calipers, they should first be cleaned with a clean piece of white paper to remove dust and dirt (place the external measuring surface of the calipers on the paper and then pull it out naturally, repeat 2-3 times).
When measuring with calipers, the measuring surface should be as parallel or perpendicular as possible to the surface of the object being measured.
When measuring depth, if the object has an R angle, it is necessary to avoid the R angle but stay close to it, and the depth gauge should be kept as vertical as possible with the measured height.
When measuring a cylinder with calipers, it is necessary to rotate and measure in sections to take the maximum value.
Due to the high frequency of use of calipers, maintenance work must be done well. They should be wiped clean and placed in a box after use each day, and their accuracy should be checked with a gauge block before use.
Before using a micrometer, it should first be cleaned with a clean piece of white paper to remove dust and dirt (place the measuring contact surface and screw surface of the micrometer on the paper and then pull it out naturally, repeat 2-3 times), then twist the knob, and when the measuring contact surface and screw surface are about to touch, use fine adjustment. When both surfaces are in full contact, set to zero, and then start measuring.
When measuring hardware parts with a micrometer, adjust the knob, and when it is about to contact the workpiece, switch to fine adjustment. Stop when you hear three clicks, and read the data from the display or scale.
When measuring plastic products, the measuring contact surface and screw should just lightly touch the product.
When measuring shaft diameters with a micrometer, measure in at least two directions and take the maximum value in sections. The two contact surfaces of the micrometer should always be kept clean to reduce measurement errors.
Application of Height Gauges
Height gauges are mainly used to measure height, depth, flatness, perpendicularity, concentricity, coaxiality, surface vibration, tooth vibration, and depth. Before measuring with a height gauge, check for any looseness in the measuring head and connecting parts.
Application of Feeler Gauges
Feeler gauges are suitable for measuring flatness, curvature, and straightness. Flatness measurement:
Place the part on the platform and measure the gap between the part and the platform with a feeler gauge (note: keep the feeler gauge in tight contact with the platform without gaps during measurement). Straightness measurement:
Rotate the part on the platform for a full circle and measure the gap between the part and the platform with a feeler gauge. Curvature measurement:
Place the part on the platform and select the appropriate feeler gauge to measure the gap between the sides or the middle of the part and the platform. Perpendicularity measurement:
Place the straight angle of the measured part on the platform, let the square ruler tightly contact the other side, and measure the maximum gap between the part and the square ruler with a feeler gauge.
Application of Plug Gauges (Rod Pins):
Suitable for measuring internal diameter of holes, slot width, and clearance. When the part's hole diameter is large and there is no suitable pin gauge, overlap two plug gauges and measure in the 360-degree direction. Fix the plug gauge on a magnetic V-block to prevent loosening and facilitate measurement.
