step Drill Bit is a drill bit that has the tip ground down to a different diameter. The transition between this ground diameter and the original diameter is either straight, to form a counterbore, or angled, to form a countersink.
The advantage to this style is that both diameters have the same flute characteristics, which keeps the bit from clogging when drilling in softer materials, such as aluminum;. Most of these bits are custom-made for each application, which makes them more expensive.
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Main parts maintenance 1. Compressor maintenance 1) The appearance of the compressor Inspection methods: Visual inspection standards: check the compressor inlet and outlet valve connection reliability, whether there is leakage; test should pay attention to the sound of the compressor to determine whether there is any abnormal 2) Voltage and current measurement and measurement tools: Clamp ammeter with a clamp ammeter operating voltage, operating current. The cable should be located in the center of the measurement loop when measuring the operating current. Measurement standards: Operating voltage range of 380V (± 10%), the operating current should not be greater than the rated input current of the motor nameplate. 3) Insulation resistance measurement Measuring tools: Megohmmeter Measuring method: In the case of unit cut off the power supply, with a megger to detect the compressor's three-phase resistance is in line with the standard. If the unit has not been activated for a long time, the crankcase of the unit should be electrically heated and heated to heat the oil chamber of the unit to evaporate Freon in the oil of the unit to improve the accuracy of measurement resistance. Note: Do not measure the insulation in vacuum , To prevent insulation breakdown caused by accident Measurement standards: Compressor motor insulation standards of not less than 500 megohms, the actual measurement should be greater than 100 megohms qualified, hot and cold insulation is greater than 8 megohm Allow to run. 4) Determination of oil: a small amount of refrigeration oil can be taken from the unit into the container, take a drop into the acid reagent bottle observed acidity, compared with the color chart. In line with the color of the color control card does not need to replace the frozen oil can be extracted from the unit a little frozen oil into the container, to minimize exposure time in the air, and then determine the acidity of the PH test paper. Meet the oleic acid requirements do not need to replace the frozen oil Check the impurities in the oil absorbent paper, if carbon precipitation or other impurities, should be replaced by frozen oil. 2. Condenser maintenance tools: pipe cleaners or chemical cleaning agents Maintenance: water-cooled condenser unit using shell and tube water-cooled condenser, condenser cleaning and maintenance work is very important, should maintain a good cooling water quality, cooling water should be regularly Chemical treatment, heat transfer tube to ensure non-scaling, maintenance can be divided into mechanical cleaning and maintenance and chemical cleaning (refer to chemical cleaning procedures). Mechanical cleaning method: 1) Close the cooling water inlet and outlet valves 2) Open the condenser front and rear cover 3) Clean the condenser cover, water chamber scaling and corrosion 4) Wash the heat transfer pipe 5 ) After rinsing with water rinse until it reaches the standard, and then cover the end cover Maintenance standards: After maintenance water chamber, heat transfer tube visual overall clean, pipe wall no significant scaling Note: 1) What way to clean, according to Condenser heat exchanger tube form to determine, to prevent damage to the inner rib tube. 2) chemical cleaning must be uniform 3) cleaning agent concentration and cleaning time should be in accordance with the factory instructions 4) rinse with water must be clean, thoroughly, do not have residue. 3. Evaporator maintenance 1) Check the chilled water quality and evaporator scaling, do a good job of sewage and water change work 2) Check the temperature difference between the water side and the refrigerant 3) maintenance should be open at the bottom of the evaporator drain valve dirt and impurities Mud discharge, if necessary, remove the blowdown valve in order to increase the sewage outfall 4) In particular, should be noted that winter is not in use to prevent freezing of water caused by vaporizer damage 5) to prevent the temperature of the package dropped to cause the induction temperature is air Temperature instead of the temperature of the evaporator, resulting in frequent low temperature alarm 6) maintenance of sewage work can refer to the following steps: (1) running the pump for 10 minutes (2) check the quality of water in the sewage outfall (3) (4) After cleaning, open the blowdown valve to the maximum, discharge the waste water (5) and then re-fill with clean water, run for 30 minutes and check the water quality again, if necessary Re-homework once