Letter from the Sub-Branch of the Machine Tool and Automation Specialty
(December 6, 1960)
Sub-Branch Committee of the Machine Tool and Automation Specialty,
Department of Mechanical Engineering, Harbin Institute of Technology, CPC

Comrades:
We have read with great pleasure your article published in the Guangming Daily on November 25, 1960,[1] and we have reprinted it in our journal. We only regret that the article is rather brief; after reading it, several of the six conclusions remain somewhat unclear. Might you consider writing another, longer article,[2] say between fifteen thousand and twenty thousand words, to explain these six conclusions in greater detail? We would also appreciate a separate analysis of the characteristics of lathes, milling machines, grinders, planers, and drills. We very much enjoy reading this kind of work from you. Your discussion of the contradictions inherent in mechanical motion has aroused considerable interest, and we should like to understand it even better. If you could satisfy this request of ours (and of the general public), we would be most grateful.
Editorial Department of Red Flag Magazine
December 6, 1960
[!]
This letter was originally written by Mao Zedong on January 28, 1960.
On December 6, he revised it in the name of the Editorial Department of Red Flag Magazine, making corresponding changes in certain parts of the text as well.
[2]
The article was authored by the Sub-Branch Committee of the Machine Tool and Automation Specialty
of the Department of Mechanical Engineering at Harbin Institute of Technology, CPC,
entitled “On the Laws Governing Internal Contradictory Motion in Machine Tools—A Case Study of ‘Modular Machine Tools.’” The article describes how the Harbin Machine-Building Machinery Plant, using spare parts from old machine tools, automobile gearboxes,
I-beams, and railway tracks, assembled various modular, mobile machine tools tailored to specific workpieces. This approach overcame the difficulty faced by small factories in manufacturing large-scale equipment, resulting in a sevenfold increase in the plant’s output value. Our faculty and students have spent the past two years studying, summarizing, and refining this experience. Machine tools are devices used for cutting and machining, and they operate under a fundamental contradiction between the cutting tool and the workpiece. It is this very contradiction that drives the development and transformation of machine tools—in lathes, milling machines, drilling machines, planers, and grinders alike. Generally speaking, the workpiece system tends to be the principal aspect of this contradiction; however, under certain conditions, the principal aspect can shift to the tool system. In conventional large machine tools, the larger the workpiece, the larger the machine must be. Modular machine tools address this contradiction by separating the workpiece and tool systems, fixing the former immovably on the ground while eliminating the need for workpiece movement. As a result, the tool system becomes independent of the size of the workpiece, allowing smaller machines to handle tasks typically reserved for larger ones and thus overcoming the shortage of big equipment. From this perspective, modular machine tools conform to the laws of machine-tool evolution: they effect a shift in the principal aspect of the machining contradiction from the workpiece system to the tool system, representing a universally significant direction in machine-tool development with far-reaching implications for future practice.
The main points are as follows:
(1) Based on our understanding of the basic contradiction in the cutting process, further research could focus on standard and specialized modular components for such machines, thereby creating conditions for their mass production.
(2) The key difference between precision, special-purpose, and ordinary machine tools lies in their working parts. By linking these tools to modular machine designs and developing specific working attachments, it would be possible to manufacture precision and special-purpose machines in ordinary machine-tool plants.
(3) Further study of modular machine tools that enable “small machines to do big jobs” holds great significance for solving problems related to the machining of large components.
(4) Many new machining methods, which simultaneously alter the properties of the workpiece during processing, are bound to trigger a further revolution in machine-tool technology.
(5) The principle of assembling machine tools from standardized drive and support components combined with specialized working parts is also applicable to other types of machinery.
(6) Recognizing the contradictory dynamics of machine tools not only clarifies the direction of our research but also strengthens our resolve to undertake a thorough reform of machine-tool education.
Red Flag Magazine reprinted this article in its twenty-fourth issue of 1960.
[3]
In its ninth and tenth combined issues of 1961, Red Flag Magazine published a more extensive article titled “Further Discussion on the Laws Governing Internal Contradictory Motion in Machine Tools and the ‘Modularization’ of Machine Tools,” drafted through collective deliberation by teachers of the Machine Tool and Automation Specialty at the Department of Mechanical Engineering, Harbin Institute of Technology, with Hou Zhenbing among the principal authors.
On December 9, 1960, Mao Zedong and others went to the airport to greet the Chinese Party and government delegation returning from a visit to the Soviet Union, led by Liu Shaoqi.