The bottom hole of the screw hole is too large
A. The material of the parts, for different parts, the size of the bottom hole Q is also selected with a certain deviation. For example, if the part you put is stainless steel, if you strictly follow the bottom hole size recommended in the table above, it is true When tapping the thread, the thread pusher is easy to fatigue or break, which is not suitable for the cost and efficiency of processing, so it can be appropriately compromised, and under the premise of ensuring the strength of the parts, the bottom is appropriately made larger. Holes, of course this is for unimportant parts, if it is for important parts, this quality compromise is not allowed.
If the parts you are processing are aluminum parts or copper parts, when making the bottom hole, you must strictly follow the bottom hole size recommended in the table above, because the hardness of the material itself is not high, and the rigidity is not good. , If the bottom hole is also made larger, the screw teeth basically have no strength, which is very easy to slip.
B. The precision of the machine tool. In fact, the diameter of the bottom hole drill is recommended in the table above. When we are actually machining, we cannot choose this too strictly, because now the processing equipment of the enterprise has processing precision. Especially in the drilling machine processing, if it is the kind of drilling machine that is in disrepair, the spindle swing is already very large, usually a φ5,2 drill bit may punch a 5.4 hole, so in this case, it is still strict If you choose according to the recommended drill size, the bottom hole is very easy to make large, and this is also very easy.The main reason why the multi-machined pits are easy to slip.
C. The screw holes of the parts are rounded. Although this kind of love brother is rare, it does exist. Either the bottom hole is rounded, or the tapping is misaligned, which leads to the contact surface of the screw. Uneven, this case is also easy to slip teeth.