What Prototype Machining Accuracy can be Achieved by Turning, Milling, Planer Grinding, Drilling and Boring?
Machining accuracy is a term used to evaluate the geometric parameters of machined surfaces, which is mainly used to characterize the precision of products. Processing accuracy is measured by tolerance grade. The smaller the grade value, the higher the accuracy.
Tolerance level
There are 20 tolerance grades from IT01, IT0, IT1, IT2, IT3 to IT18. Among them, IT01 indicates that the part has the highest machining accuracy. IT18 indicates that the processing accuracy of this part is the lowest. Generally, the factory and mining machinery belongs to IT7 level, and the agricultural machinery belongs to IT8 level. According to the different functions of the product parts, the machining precisions that need to be achieved are different, and the selected processing forms and processing techniques are also different. This paper introduces the machining accuracy that can be achieved by several common machining forms such as turning, milling, planing, grinding, drilling and boring.
Machining tolerance scale
Turning
The workpiece rotates and the turning tool performs a straight or curved movement in the plane. Turning is generally carried out on a lathe to machine the inner and outer cylindrical faces, end faces, conical faces, forming faces and threads of the workpiece.
The turning precision is generally IT8-IT7, and the surface roughness is 1.6-0.8μm.
1) Roughing is to improve the turning efficiency by using large cutting depth and large feed rate without reducing the cutting speed, but the machining accuracy can only reach IT11, and the surface roughness is Rα20-10μm.
2) Semi-finish turning and finish turning should adopt high-speed and small feed and cutting depth as far as possible. The machining accuracy can reach IT10-IT7, and the surface roughness is Rα10-0.16μm.
3) High-speed precision turning of non-ferrous metal parts with fine-polished diamond turning tools on high-precision lathes. The machining accuracy can reach IT7-IT5 and the surface roughness is Rα0.04-0.01μm. This turning is called "mirror turning".
2. Milling
Milling refers to the use of rotating multi-edged cutting tools to cut workpieces, which is a highly efficient processing method. Suitable for processing planes, grooves, various forming surfaces (such as splines, gears and threads) and special shapes of the mold. According to the same or opposite direction of the main motion speed and the feed direction of the workpiece in milling, it can be divided into forward milling and reverse milling.
The machining accuracy of milling is generally up to IT8-IT7, and the surface roughness is 6.3-1.6μm.
1) Machining accuracy during rough milling IT11—IT13, surface roughness 5-20μm.
2) Machining accuracy during semi-finishing milling IT8—IT11, surface roughness 2.5-10 μm.
3) Machining accuracy during finishing milling IT16-IT8, surface roughness 0.63-5μm.
3. Planing
Planing is a cutting method that uses a planer to horizontally reciprocate the workpiece horizontally. It is mainly used for the shape processing of parts.
The precision of planing is generally up to IT9-IT7, and the surface roughness is Ra6.3-1.6μm.
1) The roughing processing precision can reach IT12-IT11, and the surface roughness is 25-12.5μm.
2) The precision of semi-precision machining can reach IT10-IT9, and the surface roughness is 6.2-3.2μm.
3) Precision planing processing can reach IT8-IT7, and the surface roughness is 3.2-1.6μm.
4. Grinding
Grinding refers to the processing method of removing excess material on the workpiece by using abrasives and abrasive tools. It belongs to the finishing industry and is widely used in the machinery manufacturing industry.
Grinding is usually used for semi-finishing and finishing, with an accuracy of IT8-IT5 or higher, and the surface roughness is generally 1.25-0.16μm.
1) Precision grinding surface roughness is 0.16-0.04μm.
2) Ultra-precision grinding surface roughness is 0.04-0.01μm.
3) The surface roughness of mirror grinding can be less than 0.01μm.
5. Drilling
Drilling is a basic method of hole machining. Drilling is often carried out on drill presses and lathes, or on a boring machine or milling machine.
Drilling has a low processing precision, generally only achieves IT10, and the surface roughness is generally 12.5-6.3μm. After drilling, reaming and reaming are often used for semi-finishing and finishing.
6. Boring
Boring is a kind of internal diameter cutting technology with tool to enlarge hole or other circular contour. Its application range generally ranges from semi-rough processing to finish processing. The tool used is usually a single-edged boring tool (called boring bar).
1) The precision of the boring of steel materials is generally up to IT9-IT7, and the surface roughness is 2.5-0.16μm.
2) The precision of precision boring can reach IT7-IT6, and the surface roughness is 0.63-0.08μm.
Tolerance level
There are 20 tolerance grades from IT01, IT0, IT1, IT2, IT3 to IT18. Among them, IT01 indicates that the part has the highest machining accuracy. IT18 indicates that the processing accuracy of this part is the lowest. Generally, the factory and mining machinery belongs to IT7 level, and the agricultural machinery belongs to IT8 level. According to the different functions of the product parts, the machining precisions that need to be achieved are different, and the selected processing forms and processing techniques are also different. This paper introduces the machining accuracy that can be achieved by several common machining forms such as turning, milling, planing, grinding, drilling and boring.
Machining tolerance scale
Turning
The workpiece rotates and the turning tool performs a straight or curved movement in the plane. Turning is generally carried out on a lathe to machine the inner and outer cylindrical faces, end faces, conical faces, forming faces and threads of the workpiece.
The turning precision is generally IT8-IT7, and the surface roughness is 1.6-0.8μm.
1) Roughing is to improve the turning efficiency by using large cutting depth and large feed rate without reducing the cutting speed, but the machining accuracy can only reach IT11, and the surface roughness is Rα20-10μm.
2) Semi-finish turning and finish turning should adopt high-speed and small feed and cutting depth as far as possible. The machining accuracy can reach IT10-IT7, and the surface roughness is Rα10-0.16μm.
3) High-speed precision turning of non-ferrous metal parts with fine-polished diamond turning tools on high-precision lathes. The machining accuracy can reach IT7-IT5 and the surface roughness is Rα0.04-0.01μm. This turning is called "mirror turning".
2. Milling
Milling refers to the use of rotating multi-edged cutting tools to cut workpieces, which is a highly efficient processing method. Suitable for processing planes, grooves, various forming surfaces (such as splines, gears and threads) and special shapes of the mold. According to the same or opposite direction of the main motion speed and the feed direction of the workpiece in milling, it can be divided into forward milling and reverse milling.
The machining accuracy of milling is generally up to IT8-IT7, and the surface roughness is 6.3-1.6μm.
1) Machining accuracy during rough milling IT11—IT13, surface roughness 5-20μm.
2) Machining accuracy during semi-finishing milling IT8—IT11, surface roughness 2.5-10 μm.
3) Machining accuracy during finishing milling IT16-IT8, surface roughness 0.63-5μm.
3. Planing
Planing is a cutting method that uses a planer to horizontally reciprocate the workpiece horizontally. It is mainly used for the shape processing of parts.
The precision of planing is generally up to IT9-IT7, and the surface roughness is Ra6.3-1.6μm.
1) The roughing processing precision can reach IT12-IT11, and the surface roughness is 25-12.5μm.
2) The precision of semi-precision machining can reach IT10-IT9, and the surface roughness is 6.2-3.2μm.
3) Precision planing processing can reach IT8-IT7, and the surface roughness is 3.2-1.6μm.
4. Grinding
Grinding refers to the processing method of removing excess material on the workpiece by using abrasives and abrasive tools. It belongs to the finishing industry and is widely used in the machinery manufacturing industry.
Grinding is usually used for semi-finishing and finishing, with an accuracy of IT8-IT5 or higher, and the surface roughness is generally 1.25-0.16μm.
1) Precision grinding surface roughness is 0.16-0.04μm.
2) Ultra-precision grinding surface roughness is 0.04-0.01μm.
3) The surface roughness of mirror grinding can be less than 0.01μm.
5. Drilling
Drilling is a basic method of hole machining. Drilling is often carried out on drill presses and lathes, or on a boring machine or milling machine.
Drilling has a low processing precision, generally only achieves IT10, and the surface roughness is generally 12.5-6.3μm. After drilling, reaming and reaming are often used for semi-finishing and finishing.
6. Boring
Boring is a kind of internal diameter cutting technology with tool to enlarge hole or other circular contour. Its application range generally ranges from semi-rough processing to finish processing. The tool used is usually a single-edged boring tool (called boring bar).
1) The precision of the boring of steel materials is generally up to IT9-IT7, and the surface roughness is 2.5-0.16μm.
2) The precision of precision boring can reach IT7-IT6, and the surface roughness is 0.63-0.08μm.
