(1) The general gauge is unqualified, but the thread diameter is too large and the product is unqualified.
(2) The gauge is qualified, the middle diameter is reduced, and the product is unqualified.
(3) Generally, the gauge can rotate freely at any position of the thread, and the gauge can be twisted for one to two or three turns (sometimes it may be twisted for one or two more turns, but the thread head has no ring gauge end face), so it cannot be twisted. At this time, it shows that the pitch diameter of the external thread you detected is just within the "tolerance zone" and it is a qualified product.
Extended data repair and maintenance
A, don't put the working faces of two gauges together, or the two working faces will stick together, and they will be unnecessarily damaged if they are separated by external force.
B. After the gauge is used up, clean it with clean cotton yarn or soft cloth, put it in a special wooden box, and then store it in the tool cabinet; Sheet gauge can also be hung in the tool cabinet. If the weather is wet or can only be used at intervals, apply a layer of acid-free vaseline or antirust oil after cleaning. The instrument must be stored in a dry place.
C, gauges should be inspected regularly, and the general inspection period is 6- 12 months.
D, both frequently used gauges and infrequently used gauges should be externally inspected regularly to see if there is any damage, corrosion or deformation. If it is found that the pressure gauge begins to rust, it should be soaked in gasoline for a period of time in time, then carefully cleaned and coated with antirust oil.
E, when using, put the gauge in an appropriate place, such as the countertop of the tool cabinet or the wooden mat of the fixed part of the machine tool, and don't put it on the tool rest or the guide rail of the machine tool to avoid damage.
Baidu encyclopedia-thread check gauge
Baidu Encyclopedia-General Rules