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Standard Ring Gauge Diameter and Thread Ring Gauge Grade

2019-02-23

The diameter dimension of the cross section of the ring gauge in the new manufacture and use is the diameter dimension of the inner hole of the ring gauge:


1. Verification method: First, hang the weight of the instrument (according to the path of the inner hole), select the appropriate hook and standard ring gauge according to the aperture size of the ring under test, and then determine the position of the right tailstock and the left body according to the aperture size of the ring gauge under test, and lock it in. (2) Loosen the fastening screw of the worktable and lower the worktable to a lower position. (3) Place the standard ring gauge on the worktable and let the two measuring hooks be exactly at the two notches of the standard ring gauge (that is, the measured point of the standard ring gauge passes through the measuring axis). At this time, lift the worktable to the height of the working face of the standard ring gauge 1/2 and lock the fastening screw of the worktable. (4) Loosen the fastening screw of the left body to move the left body freely to the left and right sides of the hook just in natural contact with the standard ring gauge working face. Turn the differential cylinder handwheel and find out the big turning point (diameter direction) and the small turning point (axis section) in the horizontal direction of the worktable. At this time, adjust the inner dimension line of the eyepiece so that the inner dimension line of the eyepiece is exactly 1/2 of the two helix lines, and then read it as D-mark reading. D-mark reading is zero reading with standard ring gauge. With the same method mentioned above, the inner dimension of the ring gauge under test can be read out. Hole diameter size, reading D is read.


2. Verification conditions: The indoor temperature of the ring gauge in use should be (20 +2)degrees Celsius. The relative humidity of indoor air should not be higher than 65%. Vibration, noise and drifting dust which obviously affect the verification work should be avoided.


3. Prepare before verification: Verify that the measuring instruments and standard ring gauges used are qualified and within the validity period. The tested ring gauge and standard ring gauge should be scrubbed clean. The measuring equipment, the tested ring gauge and the standard ring gauge shall be kept constant temperature at the same place at the same time until the same temperature, so that the measurement can be carried out.


4. Instruments used in verification: horizontal length measuring machine, roughness comparison sample, profilometer.


The accuracy grade of thread ring gauge is classified according to thread density. The smooth gauge used to inspect workpiece thread is called "thread smooth gauge" for short. This gauge is used to inspect the large diameter of external thread and the small diameter of internal thread. The smoothness gauge of the dimension of the above mark is the smoothness gauge (thread smoothness plug gauge) used for inspecting the small diameter of threaded holes. The dimensions and allowable tolerances of this gauge are calculated according to the method specified in Appendix A of GB3934 Standard for General Thread Gauges.


The tolerance TD1 of the small diameter of the inspected screw hole can be found in Table 2 of GB/T197-2003 General Thread Tolerance. Table 2 is related to the pitch and tolerance level of the inspected internal threads. Although the pitch is known, the accuracy level of the inspected internal threads should also be known. Threads have 6 precision grades of 4, 5, 6, 7, 8, 9, etc. For example, the correct labeling should be M14*1.25-6H. However, Article 8 of GB/T197-2003 Common Thread Tolerance stipulates that for internal threads, 5H is the one without marking accuracy grade when pitch is less than 1.4, and 6H is the one without marking accuracy grade when pitch is more than 1.6. So you can look up tables and calculate them according to M14 x 1.25-6H.


Thread ring gauge and thread plug gauge have three threading grades: in metric threads, the basic deviation of H and H threads is zero. The basic deviation of G is positive, and that of e, F and G is negative.


1. H is the common location of tolerance zone for internal threads. Generally, it is not used as surface coating or very thin phosphating layer. The basic deviation of G position thread is used in special occasions.


2. G is often used for plating 6-9um thin coating, and 6G tolerance belt is used for thread before plating.


3. Thread matching is well combined into H/g, H/h or G/h. For bolts, nuts and other refined fastener threads, the standard recommendation is 6H/6g matching.


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