Why Can't The Hot-dip Galvanized Screws Be Tested With Go-no Go Gauge?

The screws we use in our daily life have national standards, and the description of a screw is M to indicate the diameter, for example, M12 screw, which means the thread diameter is 12mm. All screws in the national standard are produced by the thread rolling machine, and the thread rolling template is also formulated according to the national standard. There is also a corresponding standard for the wire diameter of the screw before turning, otherwise the thread rolled out cannot pass the go-no go gauge test, and the thread go-no go gauge test is the national mandatory standard, which is the main test method to determine whether a screw is qualified.

Can the hot-dip galvanized screws be tested with go-no go gauge? We often encounter users who ask us about this problem. They are worried about the problem of the goods when purchasing. When signing the contract, they will ask to write the test standard. Many users said that after receiving the goods, they should carry out the thread go-no go gauge test. Here we need to explain that the hot-dip galvanized screw products can not pass through the go-no go gauge. This test method is only for standard screws, and can be used for screws without any treatment, However, the screws with surface treatment cannot use this detection method.

Don't mention the hot-dip galvanized screw. Even the galvanized screw can't pass the go/no go gauge sometimes. No matter how thick the galvanizing is, the general gauge adds another layer of protective film on top of the standard, and the hot-dip galvanized protective film is the last, so it is impossible to detect the thread through the go/no go gauge. How can we detect whether it is standard? In fact, it is only necessary to measure the thickness of zinc layer. Let's look at the standard thread parameters in the national standard:

There is no need to consider the small specifications above, and the screws of this specification are not used for hot plating. At most, zinc plating is used.

The above thread is the thread standard that can be used for hot galvanizing. Its parameters are the national standards used in normal production. These are the parameters that can pass through the go-no go gauge. After the production is completed, as long as the hot galvanizing treatment is carried out, these parameters will all change, and the parameters will all change. How can the go-no go gauge be tested again?

Even some pin shaft parts are produced according to the national standard before production, and all tolerance dimensions are within the scope of detection. However, as long as the hot galvanizing is completed, its detection method cannot be carried out according to the national standard. This is not a quality problem, but the method in practical application needs to be modified. Only screws made of stainless steel can be directly tested with go-no go gauge after production.