Machining through holes is simpler than blind holes. Criterion for through holes and blind holes.It is recommended that this type of hole be machined with bits with cutting inserts at first or bored. Pre-made holes in castings or forgings are characterized by an uneven surface with high roughness, which contributes to faster wear of the twist drills. Criterion for machining in solid material or pre-made holes in the blank (figure 2).Holes for fastening screws do not require high accuracy and are made in the workshop accuracy class (IT14-15). Qualitative criterion (accuracy of geometric dimensions and surface roughness): inaccurate, accurate and very accurate holes.Most of them are usually classified simultaneously into several types. We distinguish the following criteria for the division of hole types. There are holes in almost every construction of machine parts and devices regardless of the class of parts. The hole should be machined in accuracy class 8 and the outer surface in 6. In figure 1 we can see that the Ø40H8 hole is the basis for the radial runout tolerance of the outer surface of Ø50h6. An example design of a part of the sleeve class. This article addresses issues related to drilling and reaming.įig. From a technological point of view, hole machining methods (drilling, drilling, reaming, boring, grinding, EDM) are characterized by significantly better quality effects than machining of cylindrical outer surfaces. The selection of production equipments, including machine tools, manufacturing techniques and specific machining methods depends on the usage and quality requirements (accuracy of geometric dimensions and surface roughness and hardness of the surface layer). Figure 1 shows an example of the sleeve design. How to read discussed the basics of reading a technical drawing from a technologist’s point of view. In the article Structural drawing and technology. Information about roughing holes is given in the article under the same title: Roughing holes. Selected problems of hole machining are presented below. When we pay attention to the general technological processes of these parts, in the case of classic technological processes, the general technological process of the sleeve class parts with hole-based is used. Machining holes in the sleeve and disc class parts plays an important role.
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