How to solve the problem of stainless steel thread turning（2）

4. thread roughness of the reasons and countermeasures

CNC cutting thread surface roughness after bad, fish scales and corrugated corrugated stainless steel thread cutting phenomenon is the most commonly encountered phenomenon, resulting in these phenomena are:

(1) Thread cutting tool on both sides of the blade after the corner is too small, both sides of the blade and the rear surface of the screw surface friction surface deterioration, processing must consider the angle of rotation of the screw on both sides of the actual impact angle blade.

The front corner of the thread turning tool is too small, cutting edge is not sharp enough, the chip can not be successfully cut off, but is partially squeezed or torn down, will cause the thread surface is very rough. When the current angle is too large, the blade strength weakened and easy to wear, crack, knife, more likely to cause vibration of the thread surface ripple. Therefore, according to the different materials of stainless steel to choose the appropriate rake angle. Turning strong sulfuric acid with stainless steel thread should be less than turning 2Cr13 stainless steel thread with a small rake angle on both sides of the cutting edge should have a very narrow cutting edge to avoid the edge was quickly worn. Cutting 2Cr13, 1Cr17, 4Cr13, the cutting edge should be as sharp as possible, otherwise it is not easy to achieve the required good surface roughness.

Threaded blade blade blunt, in fact, the front horn, horn from the big smaller, the chip in the process of forming a serious squeeze, so that the cutting process increases the vibration of cutting force increased, the processing of serious deterioration of the surface. Therefore, turning stainless steel thread, you must always keep the blade sharp, timely replacement of the head.

Thread tool is not fixed, the knife out of too long, arbor rigidity is not enough, or poor machine accuracy, the spindle loose, loose parts and other factors will cause vibration, so that the surface of the thread ripple. Therefore, the operation must pay attention to the operation of machine tools, tools and workpiece, the system has sufficient rigidity. Install the turning tool, in addition to ensure the installation of a solid, can not have any loosening, the tool tip should be slightly higher than the workpiece center 0.2 - 0.5mm, must not be lower than the center, so as not to bar.

When turning the thread, avoid using the straight-in method. Since the chip contact length on the left and right sides is long, it is easy to generate vibration, increase the load on the tool nose, and cause vibration and increase the chip resistance. Therefore, the best choice for the processing of stainless steel thread cross-cutting thread method. This method of alternating lateral feed, especially for large pitch thread, viscous material cutting, vibration problems to solve the most effective measures. As the left and right cross cutting edge, so wear uniform, but also extend the life of the tool.

NC cutting thread in the process of matching the amount of cutting directly affect the processing efficiency. Cutting too small will cause the tool to exacerbate wear, excessive will cause the tool to produce crushing, so the number of knives and each knife feed will have a decisive impact on the turning thread. For optimum tool life, the diameter of the workpiece should not be greater than the thread diameter of 0.14mm, and should be less than 0.05mm per tool feed. The total cut should be set at about 0.1mm. The first cut should be 150--200% of the tool nose radius (R). The maximum cut should not exceed 0.5mm. For austenitic stainless steels Avoid cutting less than 0.08mm per blade, with a small tip radius of the blade with a small blade depth, cutting the number of times may be increased accordingly.

5.Reason and Countermeasure of Unstable Thread Size in CNC Machining
Thread processing, the use of threaded ring gauge external thread "through-end" can not get or inconsistency before and after the elastic and "stop" part of the phenomenon through. The causes of these ills:
Thread shape wrong. Even if the thread diameter has reached the required size, threaded ring, plug gauge may still be fixed.
Threaded teeth. When using the thread gauge measurement, often appear by the direction of the phenomenon of restriction, which is screwed from one end of the tight, and from the other end of the screw than loose, or even "through" and "end" but through phenomenon.
Threaded bottom diameter of the car is too small, or the external thread bottom diameter is too large, will make the screw thread does not screw into the regulation, this is due to turning tool wear blunt, cutting process has squeezed the phenomenon of the thread diameter or diameter Squeeze out the burr results.
Turning the smaller diameter of the internal thread, due to the size of the cutter bar by the limited rigid rigidity, turning the process prone to "knife", as well as four large size caused by partial tolerance.
Turning the elongated screw, due to the poor rigidity of the workpiece, turning deformation process, resulting in the size of the screw on the error.
Thin-walled workpiece turning, the external thread, the workpiece due to force and the impact of cutting temperature, resulting in local deformation, will have a thread of local tolerance. Therefore, to solve the "screw gauge can not get" problem, we must take the appropriate measures for the above reasons, mainly from the correct installation and the workpiece to install the appropriate card and so on.

6. sublimation of cooling lubricating fluid in NC cutting thread

Reasonable use of lubricating fluid can improve the cutting conditions to achieve a multiplier effect. CNC cutting stainless steel thread should pay attention to: to understand the special requirements of cooling lubricating fluid

Because of the toughness of stainless steel, cutting is not easy to be separated, so the cooling fluid requires a higher cooling performance to take away a lot of heat.

As the sticky, melting of large, in the process of cutting thread prone to BUE, it should make the cooling fluid has a high lubrication performance.

Requirements of the coolant has good permeability, can be cut into the metal in the micro-gap line, the chip easily broken.

But also have a certain washing function.

7. Several suitable coolants are recommended
Vulcanized oil has good cooling performance and lubrication function, according to the different preparation methods can be divided into two kinds of direct and indirect. Direct fluidized oil formulations: mineral oil 98 (percent), sulfur 2 (percent sign). Indirect vulcanized oil formulations are: mineral oil 78 (percent) - 80%, black oil, vegetable oil 18 (percent) - 20% (percent), sulfur 1.7 (percent sign).
F43 oil suitable for stainless steel cutting cooling lubricants, stainless steel thread on the car the best results. Its formula is: high-speed oil on the 5th 83.5%, calcium sulfonate 4%, petroleum barium phosphate 4%, petroleum oxide barium soap 4%, dioxane, Zinc thiophosphate 4 (percent sign), disulfide 0.5 (percent sign).
Vegetable oil such as soybean oil, in turning the thread is conducive to better thread surface roughness and extend tool life.