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1. Selection of grinding wheel
The characteristics of the grinding wheel are determined by five factors: abrasive, particle size, hardness, binder and structure.
1) Abrasives, commonly used abrasives are oxide, carbide and high-hard abrasive systems. Aluminium grinding wheels and silicon carbide grinding wheels are commonly used on ships and factories. Alumina grinding wheel has low hardness (HV2000-HV2400) and high toughness. It is suitable for sharpening high speed steel turning tools. The white one is called white corundum and the taupe is called brown corundum.
The abrasive grain hardness of the silicon carbide grinding wheel is higher than that of the alumina grinding wheel (Hv2800 or more). It is brittle and sharp, and has good thermal conductivity and electrical conductivity. It is suitable for sharpening hard alloy. Commonly used are black and green silicon carbide grinding wheels. The green silicon carbide grinding wheel is more suitable for sharpening carbide turning tools.
2) Particle size: The particle size indicates the extent of the abrasive grain size. The number by which the abrasive particles can pass through the number of perforations per inch is used as a symbol. For example 60
Particle size refers to a screen in which the abrasive particles are just passed through 60 per inch of length. Therefore, the larger the number, the finer the abrasive grains. The rough grinding turning tool should select the grinding wheel with a small number of grinding grains, and the grinding wheel should be selected with a large number of grinding wheels (ie fine grinding grains). The medium- or medium-hard grinding wheel commonly used on ships is No. 46-Taiwan No. 0.
3) Hardness: The hardness of the grinding wheel reflects the difficulty of the abrasive grains falling off the surface of the grinding wheel under the action of grinding force. The grinding wheel is hard, that is, the surface abrasive grains are hard to fall off; the grinding wheel is soft, indicating that the abrasive grains are easy to fall off. The hardness of the grinding wheel and the hardness of the abrasive grains are two different concepts that must be clearly distinguished. Soft or medium-soft grinding wheels should be selected for sharpening high speed steel turning tools and carbide turning tools.
In addition, the bonding agent and structure of the grinding wheel should also be considered when selecting the grinding wheel. Ceramic binders (code A) and medium-sized grinding wheels are generally used on ships and factories. In summary, we should use the grinding wheel correctly according to the tool material. When sharpening high speed steel turning tools, soft or medium soft alumina grinding wheels with a size of 46 to 60 should be used. When sharpening carbide turning tools, soft or medium-soft silicon carbide grinding wheels with a size of 60 to 80 should be used.
2. The steps of sharpening the turning tool
Grinding the main flank face while grinding the main yaw angle and the main back angle;
Grinding the flank of the knives while grinding the secondary declination and the secondary relief angle;
Grind the front and grind the front corner at the same time;
Grind the knives and tips.
3. The posture and method of sharpening the turning tool
(1) The person stands on the side of the grinder to prevent the debris from flying out when the wheel breaks;
(2) The distance between the two hands holding the knife is released, and the two elbows are clamped to the waist to reduce the jitter during sharpening;
(3) When sharpening the knife, the turning tool should be placed in the horizontal center of the grinding wheel, and the cutting edge should be slightly tilted upward by about 3°~8°. After the turning tool contacts the grinding wheel, it should be horizontally moved in the left and right direction. When the turning tool leaves the grinding wheel, the turning tool needs to be lifted up to prevent the sharpened blade from being injured by the grinding wheel;
(4) When the flank is ground, the tail of the arbor is inclined to the left by an angle of a main declination; when the flank of the turret is worn, the tail of the arbor is inclined to the right by an angle of a declination;
(5) When sharpening the edge of the knife edge, usually use the left hand to hold the front end of the turning tool as the fulcrum, and use the right hand to turn the tail of the turning tool.
4. Sharpening safety knowledge
1) Before sharpening the tool, first check whether the grinding wheel has cracks, whether the grinding wheel shaft nut is tightened, and use it after trial rotation, so as to avoid the grinding wheel from breaking or flying out and hurting people.
2) The sharpening tool can't be too strong, otherwise it will slip the hand and touch the grinding wheel surface, causing work accidents.
3) Wear protective glasses when sharpening the knife to prevent the gravel and iron filings from flying into the eyes.
4) When grinding the knife, do not stand in the direction of rotation of the grinding wheel to prevent accidents.
5) When grinding a small cutter head, the small cutter head must be loaded into the cutter bar.
6) The gap between the grinding wheel bracket and the grinding wheel should not exceed 3mm. If the inlet is too large, it should be adjusted properly.
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