The mounting hole is a hole designed on the part for the installation of the part.MechanicsMost of the upper parts need to be designed with mounting holes.The size of the installation hole shall be generally larger than the size of the largest part of the equipment, and should be taken as a multiple of 0.5.The holes shall be marked on the design drawingsSurface roughness。Surface roughness refers to the size characteristics of micro geometric shapes with small spacing and small peaks and valleys on the machined surface.
The mounting hole is a hole designed on the part for the installation of the part.Most parts of the machine need to be designed with mounting holes.The size of the installation hole shall be generally larger than the size of the largest part of the equipment, and should be taken as a multiple of 0.5.The holes shall be marked on the design drawingsSurface roughness。
hole
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staytoleranceAndmeasureIn the foundation, holes mainly refer tocylinderThe inner surface of theparallelplaneOr the containment plane formed by the tangent plane).staymechanical principleIn other disciplines, there are perfect regulations on hole size and deviation.[1]
Holes are cylindrical internal or external surfaces, including those defined by a single dimension in other internal surfacespart。
Generally speaking, hole refers to the missing and closed part of an entity.
The dimensions of the holes respectively represent a single dimension of the inner surface.Dimensional toleranceIs a kind ofbasicOftolerance, whichTolerance zoneIt is one dimension, for example, a circular hole can be determined by one diameter;The square holemustDecompose Anmen intoTwoSingle size, namely length and width, and hole size and tolerance in length and width direction are given respectively according to the inner surface.
When a part has a fit relationship, the relationship between the hole and the shaft is shown asInclusionThe relationship with being contained, that is, holes areContainment surface, the axis is the contained face.Those without such fit relationship can be regarded as length dimensions.
Technically, with the increase of cutting amount, the size of the hole increases continuously.In terms of measurement method, the dimensions of holes and shafts are also different.
Evaluation criteria - surface roughness
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Surface roughnessIt refers to the degree of unevenness of the machined surface of the object.Due to the friction between the cutting tool and the workpiece surface during machining, the plastic deformation of the surface layer material during chip separation, the cutting speed and feed rate, the high-frequency vibration of the process system, and other reasons, the micro geometric shape difference consisting of peaks, valleys and spacing is formed on the surface of the parts to be machined, that is, the surface roughness is different from each other.Controlling the surface roughness of parts plays an important role in the reliability and stability of parts matching, reducing friction and wear, improving contact stiffness and fatigue strength, reducing vibration and noise, and extending the service life of parts.There are nearly 30 kinds of surface roughness evaluation parameters, including height, spacing and shape parameters.The measurement of surface roughness includes comparison method, light cutting method, light wave interferometry, needle tracing method, laser holographic interferometry, spot method, light scanning method, etc., which are respectively applicable to the measurement of different evaluation parameters and different roughness ranges.In recent years, junction computer, laser, image recognition technology and measurement methods have developed greatly.[2]
Processing method
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Reaming
stayforging and pressingIn the process, reaming is to reduce the wall thickness of the annular billet forged on the flat forging machine, crankshaft forging press or forging hammer and other equipment in the special equipment - reaming machine, so that the inner diameter and outer diameter can be expanded at the same time. This process is called reaming. It is realized by two roll rolling, so it is also called "rolling reaming", or "ring expanding".After reaming, the sectional shape of the forging blank is close to the sectional shape of the part, the geometric accuracy of the ring is greatly improved, and the utilization rate of the flat forging machine is improved.The reduction of tolerance allowance and residual block (diameter tolerance △=± 1) can save 13~17% of metal and reduce cutting time by 15~25%. Reaming is most widely used in modern bearing industry.In addition, the processing method of reaming is also used for the rims of locomotive wheels, annular parts on aeroengines, and gear blanks on trucks and tractors.
Reaming is to process the drilled, cast, forged or punched holes with a reamer, which is often used as the preparation process before reaming. It can improve the accuracy of the hole and correct the deviation of the center line of the hole.The reaming accuracy can reach IT9. This is because the reaming drill generally has 3~4 cutting edges, no transverse edge, shallow chip holding groove, larger rigidity of the tool than the drill, better cutting conditions than the drill, and better guidance than the drill, so the cutting process is stable and the machining accuracy is higher than the drill.
Sometimes it is necessary to use other types of reamer (spot facer) to process countersunk holes, tapered holes or boss planes at the hole ends.
In addition, the reamer is often combined with other tools (such as drill) to form a combined tool, so that different jobs can be carried out in one stroke, which not only improves productivity, but also ensures the mutual position requirements between the machined surfaces.[3]
Broaching hole
Use broaching method to process the hole of workpiece.
Broaching is characterized by high productivity.Since there are calibration teeth behind the tool, these teeth bear little load and seldom wear, so the workpiece hole after broaching has high accuracy and good surface roughness.The best can reach IT6.
Non ferrous metal workpieces should not be grinded, but broaching is the most appropriate method. Broaching cannot process through holes, and it is difficult to process large diameter holes or long holes.Moreover, the cost of the tool is high, the precision is not high, the batch is too small, and the use of broach is uneconomical in cost, which limits the wide application of broaching.
Boring
Enlarge the hole of the workpiece by boring.Boring is one of the most commonly used hole processing methods. It can be used as rough machining or finish machining. It can process holes of different sizes on various parts. For holes with large diameters, boring is the only processing method.
There are three boring methods:
(1) When the workpiece rotates, the cutter does not rotate and makes feed motion - boring on lathe type machine tools.
(2) The workpiece is fixed, the cutter rotates and moves in feed - boring on boring machines.
(3) When the tool rotates, the workpiece does not rotate and does feed motion - boring of special equipment in mass production is all in this way.
In order to improve the boring accuracy, floating boring cutter block can also be used, that is, the boring cutter block is loosely mounted on the cutter bar, and the cutter can be automatically adjusted. Therefore, the center of the cutter is determined by the machined hole during boring, and the hole will not be enlarged due to inaccurate installation on the cutter bar or deflection of the cutter center.
Boring is the process of enlarging the existing hole on the workpiece with boring bar and boring cutter on a boring machine, lathe or other machine tools.When boring, the workpiece is fixed on the workbench, and the boring cutter is mounted on the boring bar for rotating movement. At the same time, the workbench or boring bar makes axial movement for cutting.
