what different of hand tap and machine tap?

Another major difference between machine taps and hand taps is the material, because machine taps are usually installed on bench drills or machine tools, which belong to mechanical automatic cutting. For cutting some special material workpieces, there are multiple types of taps themselves. From materials with low hardness to materials with high hardness, there are suitable machine taps for processing and cutting. .
The raw materials of machine taps are usually HSS-E high-speed steel containing cobalt, which is a high-performance high-speed steel. Its hardness and wear resistance are stronger than ordinary HSS high-speed steel, and it is more suitable for mechanized work. Machine taps have a TIN titanium coating, which improves the wear resistance of the taps, reduces the friction coefficient, prevents adhesion, and enables faster cutting; there is also a VAP coating, which can also be understood as a tap specifically for stainless steel.
At present, there is an international method of distinguishing the materials suitable for machine taps by color, such as green ring machine taps, blue ring machine taps, white ring machine taps, black ring machine taps, orange ring machine taps, red ring machine taps, etc. Different colors represent different materials or different strengths, but the color division is not very uniform, so it is best to ask carefully and clearly in the selection to avoid making the wrong choice and causing unnecessary losses.
At work, we need to tap a thread on a plate or workpiece. First, we need to use a twist drill to drill a hole in the workpiece. Then we can use a tap to rotate inward along the hole. This rotation process can also be called tapping. By rotating inward, the inside of the smooth straight hole is cut into a thread. The tapping process is relatively simple, but the selection of tap specifications is very strict. The tapped thread must match the bolt we use, otherwise the thread will be scrapped.