{"id":2657,"date":"2026-09-25T18:13:33","date_gmt":"2026-09-25T18:13:33","guid":{"rendered":"https:\/\/endlfh.com\/2657\/"},"modified":"2026-09-25T18:13:33","modified_gmt":"2026-09-25T18:13:33","slug":"processing-knowledge-what-is-the-accuracy-tolerance-level-of-turning-milling-planing-grinding-drilling-and-boring","status":"publish","type":"post","link":"https:\/\/endlfh.com\/zh\/2657\/","title":{"rendered":"[Processing Knowledge] What Is The Accuracy "tolerance Level" Of Turning, Milling, Planing, Grinding, Drilling, And Boring?"},"content":{"rendered":"

[Processing knowledge] What is the accuracy "tolerance level" of turning, milling, planing, grinding, drilling, and boring?<\/p>\n

I come into close contact with CNC equipment every day. I have never quite understood the meaning of the tolerance grade code IT followed by the number in the Boring Encyclopedia<\/strong> . For different processing methods such as turning, milling, grinding, drilling and boring, what is the specific accuracy limit that they can achieve?<\/p>\n

If you don't understand these specific technical details, you can only make decisions based on guesswork when filling in the documents<\/strong> for the process flow. This will result in the rate of product rework never being able to be effectively reduced.<\/p>\n

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The larger the tolerance level number, the lower the accuracy.<\/h2>\n<\/p>\n

The national standard divides dimensional accuracy into 20 levels. The specific levels are from IT01, IT0 to IT18. Among them, the size of the number is inversely proportional to the width and tightness of the tolerance range. That is to say, the smaller the number corresponding to the level, the stricter the tolerance limit it represents, which will lead to an increase in the difficulty of processing.<\/p>\n

It should be noted that when the basic size value in question is less than 1 mm, within the five specific accuracy levels from IT14 to IT18, these levels actually do not exist.<\/p>\n

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In the process of production practice, what is the accuracy "tolerance level" between the IT7 level and the IT10 level? [Processing knowledge] turning, milling, planing, grinding, drilling, and boring? , there are often as many as three to four process flow gaps. Because of this<\/strong> , the two are in completely different orders of magnitude in terms of material costs and costs incurred by machine running time.<\/p>\n

When you look at the tolerance requirements marked on the drawings, you first need to confirm whether these markings are actually written in accordance with the international tolerance level, which is the so-called IT system. Never take the incorrect behavior of reading or understanding matching labels like H7 or f7 directly as IT levels.<\/p>\n

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How far can turning go from rough turning to mirror turning?<\/h2>\n<\/p>\n

The turning operation is completed on the lathe. Its main goal is to process the internal and external cylindrical surfaces, end surfaces, taper surfaces, forming surfaces and threads. In terms of conventional accuracy, its numerical range is from IT8 to IT7, and the surface roughness requirements are from 1.6 microns to 0.8 microns.<\/p>\n

When carrying out the rough turning process, the focus is on production efficiency, so a larger depth of cut and a larger feed rate are used. The accuracy achieved at this time is only as low as IT11, and the roughness is only between 20 microns and 10 microns.<\/p>\n

When finishing this process, the main cutting speed should be set very high, the feed amount should be controlled relatively small, and the radial depth of cut should also be kept within a small range. In this way, the processing accuracy can reach the range of IT10 to IT7, and the surface roughness value can be controlled between 0.16 and 10 microns. If you need to continue to improve accuracy and surface quality, you need to use diamond tools.<\/p>\n

\"\u8f66\u524a\u52a0\u5de5\u7cbe\u5ea6\u7b49\u7ea7_\u6570\u63a7\u52a0\u5de5\u516c\u5dee\u7b49\u7ea7\u8868_\u9557\u524a\u52a0\u5de5\u767e\u79d1\u5168\u4e66\"<\/p>\n

This combination allows diamond tools to be used to process non-ferrous metal parts on high-speed lathes. After such processing, the dimensional accuracy can reach IT5 level. At this time, the microscopic surface roughness can be as low as 0.01 micron. In our actual production workshop, everyone is accustomed to calling this processing method mirror turning.<\/p>\n

\"\u6570\u63a7\u52a0\u5de5\u516c\u5dee\u7b49\u7ea7\u8868_\u9557\u524a\u52a0\u5de5\u767e\u79d1\u5168\u4e66_\u8f66\u524a\u52a0\u5de5\u7cbe\u5ea6\u7b49\u7ea7\"<\/p>\n

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The accuracy of milling is slightly different between forward and reverse milling.<\/h2>\n<\/p>\n

The tool used in milling is a rotating tool with multiple cutting edges. The types of workpieces that can be processed by this tool include planes, grooves, splines, gears, as well as threads and mold shaped surfaces. Under conventional machining accuracy requirements, it can reach the standard level of IT8 to IT7, while the surface roughness range is controlled between 6.3 and 1.6 microns.<\/p>\n

In actual machining, the tool feeding methods are mainly divided into two categories: down milling and uphill milling. These two different tool feeding directions will have a significant impact on the service life of the tool and the quality of the final machined surface.<\/p>\n

The machining accuracy of rough milling is in the range of IT11 to IT13, and the surface roughness value is between 5 and 20 microns; during semi-finishing milling, the machining accuracy is adjusted to the level of IT8 to IT11, and the surface roughness is reduced to the range of 2.5 to 10 microns; when the fine milling process is involved, the machining accuracy is further raised to the IT8 level, and the surface roughness can reach a minimum level of 0.63 microns.<\/p>\n

The final finishing work of the mold cavity is basically completed by the process of precision milling.<\/p>\n

\"\u8f66\u524a\u52a0\u5de5\u7cbe\u5ea6\u7b49\u7ea7_\u9557\u524a\u52a0\u5de5\u767e\u79d1\u5168\u4e66_\u6570\u63a7\u52a0\u5de5\u516c\u5dee\u7b49\u7ea7\u8868\"<\/p>\n

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Planing and grinding each pipe<\/h2>\n<\/p>\n

The process of planing refers to a horizontal reciprocating linear cutter. Its purpose is mainly to cut the shape of parts. If it is rough planing, the accuracy level is probably between IT11 and IT12. Corresponding surface roughness values \u200b\u200bare in the range of 25 to 12.5 microns.<\/p>\n

If we talk about fine planing, the accuracy level can be improved to IT8 to IT7. At this time, the surface roughness value will become smaller, ranging from 1.6 to 3.2 microns. It is used less in new factories now. However, in the renovation work of old parts and the processing tasks of large flat plates, this method is still indispensable.<\/p>\n

The cutting method of grinding with a grinding wheel is a finishing process. It is the most widely used process in the machinery manufacturing industry. It can generally reach the accuracy level of IT8 to IT5, with a roughness value of 1.25 to 0.16 microns. Precision grinding can achieve a surface requirement of 0.04 microns. Ultra-precision grinding can achieve a roughness of less than 0.01 microns. Products such as bearing rings and gauges follow this technical route.<\/p>\n

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Don\u2019t confuse drilling and boring accuracy<\/h2>\n<\/p>\n

\"\u8f66\u524a\u52a0\u5de5\u7cbe\u5ea6\u7b49\u7ea7_\u9557\u524a\u52a0\u5de5\u767e\u79d1\u5168\u4e66_\u6570\u63a7\u52a0\u5de5\u516c\u5dee\u7b49\u7ea7\u8868\"<\/p>\n

Drilling, as the first step in hole processing, can be performed on equipment such as milling machines, lathes, boring machines, and drilling machines. However, its processing accuracy is usually only maintained at the IT10 level, and the surface roughness value fluctuates in the range of 6.3 microns to 12.5 microns. In view of the fact that after drilling is completed, it is often not possible to directly meet the matching process requirements, so subsequent finishing processes must be carried out again through additional means such as enlarging processes and reaming processes to meet standards.<\/p>\n

\"\u9557\u524a\u52a0\u5de5\u767e\u79d1\u5168\u4e66_\u8f66\u524a\u52a0\u5de5\u7cbe\u5ea6\u7b49\u7ea7_\u6570\u63a7\u52a0\u5de5\u516c\u5dee\u7b49\u7ea7\u8868\"<\/p>\n

The boring process uses a single-edged boring tool to enlarge the inner hole. This processing method can cover the entire process from semi-roughing to finishing. When steel parts are processed with conventional precision, their dimensional tolerance levels are usually between IT9 and IT7, and surface roughness values \u200b\u200bgenerally range from 2.5 microns to 0.16 microns.<\/p>\n

If the precision boring method is used, the dimensional tolerance level can be raised to the IT6 level and the surface roughness can be reduced to 0.08 microns. The hole inside the engine crankshaft will ultimately use this process to complete the final closing process.<\/p>\n

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Before choosing a process, check the function of the parts first<\/h2>\n<\/p>\n

\"\u8f66\u524a\u52a0\u5de5\u7cbe\u5ea6\u7b49\u7ea7_\u9557\u524a\u52a0\u5de5\u767e\u79d1\u5168\u4e66_\u6570\u63a7\u52a0\u5de5\u516c\u5dee\u7b49\u7ea7\u8868\"<\/p>\n

For the same part, when the required tolerance levels of the sealing surface, mating surface and positioning surface differ by two levels, the feel during assembly will become completely different. It is recommended to first observe what function the part plays in the complete equipment, and then determine its tolerance level. Never set the standard to IT5 level from the beginning, otherwise the cost and delivery cycle will be unbearable.<\/p>\n

When selecting processes such as turning, milling, grinding, drilling, and boring, the overall process route needs to be determined based on specific functional requirements. The relevant identification of the IT level should be clearly marked on the drawings, so that the production workshop can perform processing tasks according to the drawings, thus truly reducing the rework rate.<\/p>\n

Don't wait until the product jams during the assembly process before going back and modifying the process, because the resulting rework costs are enough to purchase two new tools.<\/p>\n

\"\u8f66\u524a\u52a0\u5de5\u7cbe\u5ea6\u7b49\u7ea7_\u6570\u63a7\u52a0\u5de5\u516c\u5dee\u7b49\u7ea7\u8868_\u9557\u524a\u52a0\u5de5\u767e\u79d1\u5168\u4e66\"<\/p>\n

May I ask which IT level is most likely to get stuck in your workshop work? You are welcome to post your geographical location information in the comment area. At the same time, please click the like and favorite buttons. Next time you need to write a process sheet, you can read it out for reference, so that you can avoid asking the master for advice again.<\/p>\n

\"\u6570\u63a7\u52a0\u5de5\u516c\u5dee\u7b49\u7ea7\u8868_\u9557\u524a\u52a0\u5de5\u767e\u79d1\u5168\u4e66_\u8f66\u524a\u52a0\u5de5\u7cbe\u5ea6\u7b49\u7ea7\"<\/p>\n","protected":false},"excerpt":{"rendered":"

Tolerance level refers to the level that determines the degree of dimensional accuracy. The national standard stipulates that it is divided into 20 levels, from IT01, IT0, IT1, IT2 to IT18. The larger the number, the lower the tolerance level, the greater the range of allowable changes in size, and the less difficult the processing.<\/p>","protected":false},"author":1,"featured_media":2658,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28],"tags":[689,447,759,2321,757],"class_list":["post-2657","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-machining","tag-grinding","tag-machining-accuracy","tag-milling","tag-tolerance-classes","tag-turning"],"_links":{"self":[{"href":"https:\/\/endlfh.com\/zh\/wp-json\/wp\/v2\/posts\/2657","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/endlfh.com\/zh\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/endlfh.com\/zh\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/endlfh.com\/zh\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/endlfh.com\/zh\/wp-json\/wp\/v2\/comments?post=2657"}],"version-history":[{"count":0,"href":"https:\/\/endlfh.com\/zh\/wp-json\/wp\/v2\/posts\/2657\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/endlfh.com\/zh\/wp-json\/wp\/v2\/media\/2658"}],"wp:attachment":[{"href":"https:\/\/endlfh.com\/zh\/wp-json\/wp\/v2\/media?parent=2657"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/endlfh.com\/zh\/wp-json\/wp\/v2\/categories?post=2657"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/endlfh.com\/zh\/wp-json\/wp\/v2\/tags?post=2657"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}