1、 Grinding method of thread
According to the different forms and feeding methods of grinding wheel used for thread grinding, there are three common processing methods:
1. Single line grinding wheel, longitudinal feed: the production efficiency is low, but the grinding thread accuracy is high, which is mainly used for single piece and small batch production.
2. Multi line grinding wheel, longitudinal feed: high production efficiency, commonly used in mass production.
3. Multi line grinding wheel, cut in feed: high production efficiency, commonly used in mass production.
For threads with a pitch greater than 3mm, the threads shall be pre machined before grinding; For threads with a distance of less than 3mm from the screw, the thread can be directly ground without pre machining. This method is suitable for machining workpieces with small screw pitch and thread length less than the width of the grinding wheel.
2、 Installation and use of grinding machine tools
1. Installation of machine tool
(1) Thread grinding is carried out on a special thread grinder. If processing single pieces and small batches of precision threads, the machine tool should be installed in a constant temperature room with the temperature controlled at 20 ± 1 ℃. If processing large batches of threads, the machine tool can be installed in an ordinary workshop with better conditions.
(2) The machine tool should be installed on a solid foundation and equipped with an anti vibration ditch, away from the external vibration source. The horizontal tolerance of machine tool installation shall be within the specified range of machine tool.
2. Use of machine tools
(1) It takes a certain time for the machine tool from Startup to thermal stability. It should be idled for more than half an hour during rough grinding and more than 1 hour during fine grinding; When grinding threads with high roughness, it should be idled for more than one and a half hours.
(2) The pressure adjustment of the tailstock center should be appropriate, which can be larger for thick and short workpieces and smaller for slender workpieces.
(3) In order to ensure the dimensional accuracy of parts, when grinding close to the final size, the transverse feed should not be too large, generally within 0.01mm.
(4) During fine grinding, grinding should be carried out from tailstock to headstock as far as possible to reduce pitch error.
(5) The universal thread grinder is equipped with a set of internal thread grinding device. The workpiece is clamped in the four jaw chuck, and the end face and inner hole of the workpiece are corrected to the specified accuracy with a table before grinding. When dressing the grinding wheel, the tooth angle of the grinding wheel can be corrected by trial grinding of thin steel sheets.
(6) Grinding multi head threads uses the indexing chuck attached to the machine tool. The number of teeth of the indexing chuck can be selected as required.
(7) During grinding, the grinding fluid must be fully sprayed in the grinding area to ensure rapid cooling of the workpiece and scouring of wear debris. It is especially important when grinding thread with multi line grinding wheel. The capacity of the grinding fluid tank should be large enough and equipped with a reliable filtration system to ensure the cooling and cleaning of the grinding fluid.