The hottest method to control the accuracy of dril

2022-10-03
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The method of controlling the accuracy of drilling position

drilling is a required test in the fitter operation assessment, and the score accounts for 1 of the whole assessment. Metallography mainly refers to the branch of material science/5 ~ 1/4 that analyzes and characterizes the microstructure, macrostructure and fracture structure of materials with the help of metallographic microscope and stereomicroscope, among which the requirements for the accuracy of drilling position account for more than 3/5 of this part. Therefore, controlling the accuracy of drilling position is the basic skill that fitters must master

The control of the position accuracy of the hole is essentially the mutual correct position control process of the drill bit and the workpiece in the drilling process. In order to assess the operator's operating skills, it is required that the hole position adjustment during drilling can only be a manual and dynamic control process, and drilling jigs and other fixtures are not allowed to be used. Therefore, the position of the hole this time Jinan new era Gold Testing Instrument Co., Ltd. wants to share with you is the concrete pressure. In addition, the structure and operating method accuracy of GA testing machine are subject to the scoring, machine tool accuracy, workpiece and bit clamping, bit grinding quality Due to the influence of some uncertain factors such as the adjustment of workpiece position and machine tool cutting parameters, plus certain processing skills and necessary assurance measures, serious out of tolerance will occur when the position accuracy of the hole is required to be high

how to effectively avoid and eliminate the out of tolerance of hole position is the key to control the hole quality during drilling. During the drilling operation, in addition to the correct marking, drilling the bottom hole, correcting the deviation in time and accurately, and filing the position of the bottom hole are the basis to ensure the position accuracy of the hole

scribe

since the position accuracy at the beginning of drilling basically depends on the position of the sample punching hole, the position accuracy of the dynamic control hole is transformed into the punching accuracy of the sample punching hole to a certain extent. Considering the important role of the punching hole in controlling the position accuracy of the hole, attention should be paid to the following during the specific operation: ① select a height ruler with a sharp knife head, so that the groove mark of the hole centerline on the machining surface is deep, and use the resistance of the groove mark of the hole centerline when the punching hole moves to determine the correct position of the punching hole. ② In order to reduce the size deviation between the center of the visual hole and the ideal position, the control circle or control box of each size hole should be drawn (due to the scoring accuracy, the method of drawing the control box is recommended), and the caliper measurement method should be used to ensure the position accuracy while visually inspecting during the drilling process. ③ Since the correction method of filing and drilling and expanding the bottom hole is transferred to the correction of the position deviation of the sample punching, the number of times of expanding and correcting the position of the bottom hole can be reduced more effectively, and the operation and processing time can be shortened. Therefore, after the sample punching, the position accuracy should be carefully checked and necessary correction should be made

clamping of workpiece and drill bit

because it is difficult to ensure the position accuracy only by visual inspection during the drilling process, vernier caliper and other measuring tools must be used for measurement. In order to facilitate measurement, the workpiece should be installed a certain size higher than the jaw of the machine vice. The clamping of the drill bit should be as short as possible to improve its rigidity and strength, which is more conducive to the guarantee of its position accuracy

drill bottom hole

the position of bottom hole is correct or the out of tolerance is small, which can effectively reduce the times of reaming and correcting the position of bottom hole, shorten the operation and processing time, and play a particularly important role in improving the processing accuracy and processing efficiency

step 1: selection of drill diameter. The drill diameter is too small, the strength is weak, and it is easy to break during processing; When drilling and expanding for deviation correction, the drill bit bends and deflects, resulting in processing in the opposite direction of the deviation to be corrected, which increases the position error of the original hole. The diameter of the drill bit is too large, the horizontal edge is long, and the centering performance is poor. The times of filing and drilling and expanding the position of the deviation correction hole are relatively reduced. If the hole diameter of the bottom hole is larger than that specified in the drawing, the out of tolerance bottom hole may not be eliminated. Therefore, the appropriate drill bit should be selected according to the actual situation, because the center drill can not only be well positioned, but also ensure sufficient stiffness and strength, so it is appropriate to select the center drill when drilling the bottom hole

step 2: align the sample punching hole. There are two methods to align the center drill with the sample punching hole. One is to rotate the drill chuck by hand and move the flat tongs or rotate the workbench of the bench drill to align the center drill with the sample punching hole. Second, the relatively regular workpiece is in a floating state as far as possible, and the workpiece position is slightly moved by the pulling of the drilling force, so that the drill bit and the sample punching hole are automatically aligned

step 3: detection. In order to improve the detection accuracy of the hole position, necessary corrections should be made to the detection results: first, measure the nearest and farthest points of the two hole walls and take the average value. The second is to insert the corresponding measuring rod after drilling, so as to reduce the influence of the non-linear factors of the vernier caliper measuring claw on the measurement results

position control of reaming

the position of the bottom hole is determined to be correct after detection, and effective measures should be taken to prevent new position deviation of the hole position in the process of reaming. First of all, the vertex angle of the drill used for reaming should be small, so as to reduce the radial eccentric force and vibration during drilling and increase the role and effect of automatic centering. Then turn the drill chuck by hand, and move the flat tongs or rotate the workbench of the bench drill, so that the two main cutting edges of the drill bit contact the hole wall of the end port of the drill bit of the original bottom hole at the same time, and then start the drilling machine to drill. This operation can basically ensure that the position of the original bottom hole remains unchanged

hole reaming and deviation correction

the out of tolerance of hole position is 0 For the bottom hole within 20mm, it can be solved by pushing the workpiece in the direction of deviation correction and gradually increasing the diameter of the drill bit. (Note: in order to weaken the role of automatic centering of the drill bit since it was first discovered in 2004, the vertex angle of the drill bit should be appropriately increased)

file correction

the out of tolerance of the position of the hole is greater than 0 20mm bottom hole, if the above method is still adopted, it is bound to increase the number of hole reaming and the occupation of drill bits with different specifications and sizes, and prolong the time of deviation correction. The problem can be solved by using the round file trimming technology to remove the excess offset allowance, and then drilling and expanding

step 1: relevant measurement and calculation: first measure the size error and shape and position error of the bottom hole, such as out of tolerance, relative to the ideal position, and calculate and analyze the position error value of the hole. Then, determine the direction of filing the bottom hole (the direction of filing the bottom hole, which is the connecting line direction from the location center of the actual hole to the center of the ideal position) and the shape of the filing hole (the shape of the filing hole should be close to the ellipse, the geometric center of the ellipse coincides with the center of the ideal position, the short axis of the ellipse is the diameter of the original bottom hole, and the minimum bottom hole diameter to eliminate the position error of the hole is the long axis of the ellipse)

step 2: select file and filing method. The diameter of the selected filing round file is slightly smaller than the diameter of the original bottom hole. If the diameter is too large or equal to the bottom hole diameter, the round file cannot be inserted into the bottom hole or it is difficult to file when filing. If it is too small, it is easy to file it into pear shape, so that the drill bit is under asymmetric force, and the position deviation error of new holes will occur when drilling. When repairing the file, you can manually repair the file on the bench vice, or you can clamp the round file in the drill chuck with the help of the rotary movement of the drilling machine spindle, move up and down, and push the workpiece for processing. File the sheet from one end of the bottom hole; When the workpiece is thick, the through hole should be filed from both ends of the bottom hole to reduce the non vertical error between the inner arc surface of the file and the end face of the orifice

step 3: ream. The diameter of the selected reaming bit should be greater than the size of the long axis of the ellipse in the middle plane of the workpiece thickness. Short drill bits, small top and back angles, and low-speed cutting should be used for reaming

step 4: inspect whether the dimensional accuracy and shape and position accuracy of the inspection hole are qualified. If it is unqualified, repeat the above process until it meets the technical requirements specified in the drawing

in the process of drilling, the principle of first datum and then general, first high precision and then general should be followed, that is, the holes on the datum position should be processed or guaranteed first, or the holes with relatively high dimensional accuracy and shape and position accuracy requirements

how to effectively avoid and eliminate the out of tolerance of hole position is the key to control the hole quality during drilling. However, due to many influencing factors, repeated intensive training is required to achieve the purpose of completely controlling the position accuracy of the hole. This is a long process of gradual improvement of accuracy. (end)

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