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Hydraulic valve main valve spool of slide valve and cone valve two kinds.With cylindrical shaft shoulder of valve core, moving along the axial direction to connect or disconnect oil cylinder valve usually refers to the slide valve.Through the change of valve opening, the flow changes, make traffic regulation.By changing the gaps between the cone valve core and valve seat, to connect or disconnect the oil valve, called the cone valve.Cone valve can be completely cut off the oil, the sensitivity of the impurities in the oil pollution is small, simple structure, easy.So as for the hydraulic valve cone valve and valve is one of the main structure.Because the two different kinds of structure, so the processing method has both similarities and also have differences.Are usually made by professional manufacturers.With the need of valve core on the valve body movement, so the size of the gap to ensure good sealing, and to ensure the smaller resistance movement.In actual production, generally adopt the method of parts with deputy research with each other to ensure that the small fitting clearance.But in batch and mass production, need the valve core are interchangeable, enhanced fit clearance will be appropriate at this time, this can cause the occurrence of leakage.For batch and mass production of tolerance and fit clearance of valve core and valve body, recommended as follows: hydraulic valve body and valve core mm nominal diameter tolerance and fit body tolerance of valve core tolerance minimum clearance maximum clearance 0.006 0 + 6 + 12 + 0-0.004 0.0025 0.0125 0.0075 0 + 0-0.005 0.0050 0.0175 0.010 0 + 20 + 0-0.006 0.0075 0.0233 0.0125 0 + 25 + 50 + 0-0.0075 0.0125 0.0325 0.015 0 + 0-0.010 0.020 0.045 0.020 0 + 75 + 100 + 0-0.0125 0.025 0.0575 0.020 0 + 0-0.0125 0.032 0.0645 0.025 0 + 125 + 200 + 0-0.015 0.043 0.083 0.030 0 + 0-0.020 0.050 0.100 for reciprocating or rotary movement of the valve body and valve core, suggest taking minimum clearance.Maximum clearance value is equal to the minimum clearance value plus the sum of two parts of tolerance.Minimum clearance value can be added in the name of the hole size, also can by size minus in the name of the valve core.Specific valve core processing need according to the number of products and the size of the factories to decide, specific requirements can refer to the manual parts process and other professional books.In short for processing and manufacturing of valve core must consider the following a few big problem, when it is necessary to test means, so as to ensure the high quality and high reliability of the valve core.(1) on the hydraulic valve core fluid power (on the slide valve fluid power, function in the axial force on the cone valve);(2) the pressure of the hydraulic valve core flow characteristic;(3) the flow coefficient of the hydraulic valve core;(4) the leakage of hydraulic valve core (mainly refers to the slide valve);(5) the stability of the hydraulic valve core;(6) the vibration of the hydraulic valve core,(7) air pockets of hydraulic valve core.