For the measurement of the diameter of the inner hole of steel pipes, precision steel pipes, and some mechanical parts, there are measurement methods such as direct measurement, indirect measurement, and comprehensive measurement.
First, direct measurement: the most commonly used measurement method. This method is often used in the production and inspection process of our precision steel pipes.
The method of directly measuring the aperture using two or three points of positioning is also the most commonly used aperture measurement method. Depending on the accuracy level, size, and quantity of the apertures being measured, general length measurement tools that can measure apertures can be used, such as vernier calipers (see calipers), tool microscopes, universal length ratiometers, and horizontal length measuring instruments (see length measuring machines), horizontal optical meter (see comparator) and pneumatic measuring instrument, etc.; special aperture measurement tools can also be used, such as inner diameter micrometer, inner diameter dial indicator and dial indicator, inner diameter micrometer, electronic plug gauge and the use of pneumatic, Aperture measuring instruments based on optical, electrical and other principles.
① Using lever mechanism to measure holes: This method is often used in hand-held hole diameter measurement tools, such as inner diameter dial indicators, mechanical or electrical inner diameter micrometers, etc. The difference between the measured aperture size and the calibration ring gauge aperture is read from a dial indicator, or mechanical or electrical micrometer through a lever mechanism. The measuring aperture range of this type of hole-measuring tool is generally 10 to 800 mm, and the measurement accuracy of the inner diameter micrometer can reach 3 to 5 microns.
② Using the inclined wedge principle to measure holes: This method is also commonly used in hand-held aperture measuring tools. Among them, the inner diameter dial indicator used to measure small holes can measure holes as small as 0.5 mm in diameter. When the measured aperture compresses the probe and moves the measuring rod with the cone, the aperture error can be read from the dial indicator or micrometer. The three-point positioning method is suitable for measuring holes with a diameter of more than 3 mm. When the measuring rod rotates, the fixing nut moves the measuring rod forward, and the cone with the spiral boss on the top of the measuring rod causes the three measuring heads to move outward and contact the hole being measured. Read the measured aperture size from the scale on the fixed sleeve and micron cylinder. Such aperture measuring tools include three-jaw inside micrometers.
③The measurement of the high-precision aperture by a seat-type aperture meter made of pneumatic, optical, electric, and other principles must be carried out under constant temperature conditions close to 20°C. The light wave interference aperture measuring instrument measures the aperture in a range of 1 to 50 mm, with an accuracy of ±0.5 microns.
Second, indirect measurement: When there is a dispute between the supplier and the demander about the size of the steel pipe, we will consider using this method to verify the accuracy of the measurement data. First measure the function related to the aperture, and then convert the aperture size. There are mainly two methods:
①Use the principle of three points to determine a circle, measure the coordinate values of any three points on the circumference of the hole to be measured, and then find the coefficients D, E, and F in the equation x2+y2+Dx+Ey+F=0, and then the diameter of the hole to be measured can be obtained according to the calculation formula. This method is generally used on coordinate measuring machines with electronic computers;
② Use a roller with a known diameter to roll against the wall of the hole to be measured, measure the circumference of the hole to be measured, and then calculate the hole diameter. This method is suitable for measuring holes with a diameter greater than 500 mm and a continuous surface. The measuring tool that applies this method is called a large-diameter measuring instrument and is also commonly used to measure the outer diameter of large workpieces. (However, this measurement method is not very accurate. Some scholars have studied methods such as multi-roller measurement and computer simulation calculations to improve accuracy.)
Post time: May-23-2024