When it comes to difficult processes in processing, tapping should fall into the most difficult category. In general metal processing, it is usually the rapid removal of metal and the formation of a smooth surface, the process is ended, but the tapping is not exactly the same. First of all, the thread formed after tapping must meet the standard requirements and can be screwed with the matching fasteners. Secondly, it is very simple to exit the tool at the end of the general process, and the time it takes to exit the tap after tapping is completed. Threads take as much time. All of this makes tapping an indispensable and slow and annoying process. In addition to the above common problems, other factors will increase the difficulty of tapping: these factors can be mainly divided into two categories related to materials and operations. In any case, the correct choice of tap will have a very different effect on the tapping effect: attack a lot of holes, tap a hole or completely attack. The following is a brief introduction of some of the work that field technicians and tool manufacturing technicians have done to overcome the difficulty of tapping. Problem with workpiece material Tapping on difficult-to-machine materials can be a laborious and expensive task. Dan Gajolosik, engineering manager at Besly Products, points out that the main difficulty in tapping on difficult-to-machine materials is that the heat generated during cutting and the shrinkage of the workpiece material encase the tool. Titanium alloys are the most obvious in this regard. He suggested that when tapping on this material, the tap should have a larger toothed back and a reverse taper to prevent the tap from working. In addition, Gajolosik pointed out that the strength of the tap base is also important. Due to the high hardness and strength of the workpiece, the tip of the tap is often blunt. In this case, high-performance high-speed steel taps are recommended, which have high toughness, red hardness, and resistance to deformation and wear. Paul Motzel, a specialist in tap application at Guhring, says that when designing a tap for hard materials, it is critical to use a small rake angle, which allows for greater support during tap cutting. Stellite is a nickel-based superalloy that is one of the most difficult materials to process. Mike Brown is the owner of a computer integrated processing company and received a number of orders. This material is used to process the fan blades of aerospace engines. Each engine has 25 pieces, and each piece is to be machined with a screw-shaped through hole of 10~32UNF-2B, which is used for screwing into the top wire when the blade is removed. At the beginning, the company learned that this material has a strong "memory" function - the tendency to retract after processing. In order to overcome this shape problem, Brown first made the bottom hole bigger: the drawing specified the bottom hole to be 0.159′′ (4.0386mm) in diameter, actually drilled 0.161′′ (4.0894mm), which was 0.002′′ (0.0508mm). This can make the tapping work lighter. However, when the first tap test was conducted, it was found that only 1 or 2 holes were cracked. Brown found that the taps emitted high-pitched noise, just like the brakes on the bus. So I realized that there was something wrong with it. The taps used in the Brown test are priced at $18 each and can only be used for 1 or 2 holes. He tried to find a more suitable tap by repeatedly trying to make the number of holes processed a little more. Finally, it was determined that 4 holes could be processed using the high-speed steel Exotap type tap produced by OSG Tool and Die Co., Ltd. Brown said: "These taps cost $12 to $15 each, and they cost $3 to $4 per hole. The price is high. However, the cost of processing this material is not high, but if you use nearly $20. The tap, only one hole, is unacceptable." Is there any further use of carbide taps? Brown believes it is not feasible. He said: "For such workpieces, drilling with carbide tools is possible. But it is too hard, and the carbide taps are less tolerant of the processing conditions, so it is not suitable." However, this does not mean that the carbide tap is completely unworkable for the machining of the workpiece. In fact, after the Exotap tap is tapped, the workpiece is removed from the fixture. The second step is to manually correct the tapped hole with a $60 carbide tip. Brown believes that it is not a good thing to choose the right tap. It is also important to choose the right lubricant. At the suggestion of a craftsman friend, he changed the lubricant of the tap. Castrol's tap grease is currently used, and the grease is applied to the tap before each tapping. Dan Welter, the foreman of Diamond Tooling, provided another example of tapping difficult materials. The material is a super austenitic stainless steel Al 6XN, which has anti-oxidation and corrosion properties and is widely used for conveying liquid parts such as original parts. The material has high chromium, nickel and molybdenum contents (20%, 24% and 6%, respectively) and has a high hardness (HRB88) and a tendency to harden the work. This is a printer's ink delivery pump. Welter wants to tap six 4 to 40 threaded through holes on the part, three holes per side, and a hole depth of 6.35 mm. It is required to drill the bottom hole once on the workpiece and then tap. Initially, he used standard high-speed steel TiN coated taps, but the material hardness was too high, causing the tap to crack. After testing six different high-speed steel tapers, Welter finally abandoned the idea of ​​using standard taps to solve the problem and began to seek new solutions. 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