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Numerical control machining accuracy tolerance class

Views: 1     Author: Site Editor     Publish Time: 2022-04-15      Origin: Site

We deal with CNC processing every day, do you know car, milling, planing, grinding, drilling, boring respectively can achieve what kind of precision tolerance level?

The tolerance grade refers to the grade to determine the accuracy of the size, the NATIONAL standard is divided into 20 grades, from IT01, IT0, IT1, IT2 ~ IT18, the greater the number, the lower the tolerance grade (machining accuracy), the greater the allowable size variation range (tolerance value), the less difficult the processing.

According to the different functions of product parts, different processing accuracy needs to be achieved, and different processing forms and processes are selected. This paper introduces the machining accuracy of turning, milling, planing, grinding, drilling, boring and other common machining forms.

1. Turning

The workpiece rotates and the turning tool moves in a straight line or curve in the plane. Turning is generally carried out on a lathe to process the internalconstruction machinery cardan drive shaft - Xinsanming and external cylindrical surface, end surface, conical surface, forming surface and thread of the workpiece.

The turning accuracy is generally IT8~IT7, and the surface roughness is 1.6~0.8μm.

1)  Rough turning adopts large cutting depth and large feed to improve turning efficiency without reducing cutting speed, but the machining accuracy can only reach IT11, and the surface roughness is Rα20~10μm.

2)  Semi-finishing car and finishing car try to use high speed and small feed and cutting depth, machining accuracy up to IT10~IT7, surface roughness Rα10~0.16μm.

3)  The precision of non-ferrous metal parts can reach IT7~IT5, and the surface roughness is Rα0.04~0.01μm, which is called "mirror turning".

2.  Milling

Milling refers to the use of rotating multi - edge cutting tools to cut workpiece, is a high - efficiency processing method. Suitable for machining plane, groove, all kinds of forming surface (such as spline, gear and thread) and mold special surface, etc. According to the direction of the main motion speed in milling and the workpiece feed direction of the same or opposite, and divided into along milling and inverse milling.

The milling accuracy is generally up to IT8~IT7, and the surface roughness is 6.3~1.6μm.

3. Planing

Planing machining is a cutting method of horizontal relative straight reciprocating motion of workpiece with planer, which is mainly used for the shape machining of parts.

The machining accuracy is generally up to IT9~IT7, and the surface roughness is Ra6.3~1.6μm.

1)  The machining accuracy of rough planing can reach IT12~IT11, and the surface roughness is 25~12.5μm.

2)  The semi-finishing planing machining accuracy can reach IT10~IT9, and the surface roughness is 6.2~3.2μm.

3)  The precision of fine planing can reach IT8~IT7, and the surface roughness is 3.2~1.6μm.

4. Grinding

Grinding refers to the processing method of cutting redundant materials on the workpiece with abrasives and abrasives. It belongs to the finishing process and is widely used in the machinery manufacturing industry.

Grinding is usually used for semi-finishing and finishing, the accuracy can reach IT8~IT5 or higher, the surface roughness is generally grinding 1.25~0.16μm.

1) Surface roughness of precision grinding is 0.16~0.04μm.

2)  Surface roughness of ultra-precision grinding 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 processing. Drilling is often carried out on drilling machines and lathes, but can also be carried out on boring or milling machines.

The machining accuracy of drilling is low, generally can only reach IT10, 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 cutting tool to expand the hole or other circular contour of the inner diameter cutting process, its application range is generally from half rough machining to finishing machining, the tool is usually a single edge boring cutter (called boring bar).

1)  The boring accuracy of iron and steel materials can reach IT9~IT7, and the surface roughness is 2.5~0.16μm.

2)  The machining accuracy of precision boring can reach IT7~IT6, and the surface roughness is 0.63~0.08μm.

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  : +86 29 86033971
 : +86 29 86033972
  :  zhao.wanbao@dcsxsm.com
  : The Innovation Industrial Park, No.36, Jingwei Road ,Xi'an Economic and Technological Development Zone,Xi'an City,Shaanxi Province,China
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