Abstract: fitter is a technology with a long history, which can be traced back to 2000 years ago. With the development of science and technology. Many fixture processing jobs have been replaced by mechanical processing, but assembly fixture processing, as an indispensable process in mechanical manufacturing, still plays a very important role. For example, the assembly, maintenance and inspection of mechanical products all need the work of the fitter, and the fitter is also a necessary type of work for the final manufacture of all mechanical equipment, which shows the position of the fitter in mechanical manufacturing, so it is very important to master the technical points of the fitter for mechanical manufacturing.
Keywords: assembly file drilling and sawing assembly drawing
Introduction: The locksmith works by hand and uses various tools to finish the processing of parts. Compared with machining, locksmith has high labor intensity, low production efficiency and low manufacturing accuracy, but it is also an inconvenient and difficult type of work in machining, especially assembly locksmith, which is related to the dimensional accuracy, position accuracy and shape tolerance of products, that is to say, assembly locksmith is related to the quality of products and whether they are qualified or not. However, only by understanding the assembly process regulations can we improve labor productivity and ensure product quality. Only by strictly following the process regulations can we ensure the smooth assembly work, reduce the cost and increase the factory income. Therefore, as long as we know the precautions of assembly, we can give full play to our own strength in production, which is also the purpose of this paper.
A. Basic skills of assembly fitter
The basic skills of assembly fitter mainly include marking, drilling, filing, sawing, reaming, working thread and turning thread, as well as assembly, debugging, inspection and trial operation of mechanical parts. To be a qualified fitter, we should not only process qualified products, but also have the knowledge of safe and civilized production to adapt to the production slogan of "safety first, production second". The following are the basic skills and precautions of locksmith.
(a) crossing
Scribing is the operation process of drawing processing boundaries or drawing points, lines and surfaces as benchmarks on a blank or semi-finished product according to drawings and technical requirements. Marking requires clear and consistent lines. The fixed-length positioning size is accurate, and the marking accuracy is generally required to be between 0.25 mm and 0.5 mm. Marking can determine the machining allowance of the workpiece; Make the processing have obvious size restrictions; Can also find and deal with unqualified blanks.
Marking tools include marking needle, marking gauge, marking disk, steel ruler, sample punch, etc. The marking tool should be separated from the blank, so as to avoid the burr of the blank scratching the marking tool and affecting the accuracy of the tool. At the same time, it should be maintained in time to avoid rust of tools. Before scribing, first of all, we should understand the drawings and process requirements and make clear the scribing task; Check whether the blank and workpiece are qualified; Then, cleaning and painting the marked part; Determine the marking benchmark; Select the scribing tool for scribing.
The steps of marking are usually as follows:
1 read the drawings, know in detail the parts that need to be marked on the workpiece, clarify the functions and requirements of the workpiece and the marked parts, and understand the related processing technology.
2 Selected marker datum
3. Check the error of blank preliminarily and color the blank.
4 Correct installation of workpieces and selection of marking tools
5 underline
6 Check the accuracy of the marks in detail against foreign drawings to see if there are any omissions.
7 punch holes in the line
(2) filing
Filing is widely used, and it can file flat surfaces, curved surfaces, internal and external surfaces, grooves and other surfaces with complex shapes. The accuracy can reach 0,065,438+0mm, and the surface accuracy can reach r0,8um. Whether the file is held correctly or not has a certain influence on the quality of the file, the exertion of the file strength and the fatigue degree of people. The correct grip method is to hold the handle tightly with the right hand, hold the handle end against the palm of your hand, put your thumb on the upper step of the handle, hold it with the other four fingers of the middle finger of your left hand, hold the front end of the file with the ring finger, press the root of your thumb on the file head, and naturally close your index finger and little finger. The standing position of the file is similar to that of a chisel. It should be natural and easy to exert force to adapt to different filing requirements. The center of gravity of the body should fall on the left foot, the right knee should be straight, and the left knee should flex and stretch with the reciprocating motion of the file. When filing a plane, the file must keep a horizontal and straight filing motion. Before filing, the pressure exerted by the left hand changes from large to small, and the pressure exerted by the right hand changes from small to large. Generally, the file is filed about 40 times a minute.
Precautions for archiving:
1 File handling should be firm, and do not use files to handle cracked files.
It is not allowed to blow iron filings with your mouth, and it is not allowed to clean iron filings with your hands.
3 file placement shall not expose the clamping table.
4 When clamping the machined surface, protective sheets should be used, and wooden mats should be added for larger workpieces.
(3) sawing
Sawing is a processing method of cutting or sawing materials or workpieces with a saw. Skills and methods: Hold the handle of the saw bow with the right hand, press the thumb on the index finger, control the direction of the saw bow with the left hand, put the thumb on the back of the bow, and hold the index finger, middle finger and ring finger at the front end of the saw bow. The posture is basically the same as that of filing. The sawing method is that when moving forward, the left hand is tilted upwards, and the right hand is pressed downwards. When returning, the right hand is lifted upwards, and the left hand naturally follows backwards, about 40 times a minute.
Matters needing attention when sawing:
1 When the workpiece is about to be sawed off, reduce the pressure to prevent the foot from being hurt when the workpiece breaks.
2 when sawing, control the strength to prevent the saw blade from suddenly getting out of control and hurting people.
When sawing, the vertical line between the eyes and the saw blade coincides, and one side is crooked.
4 the saw jump is installed too tightly or moves too fast, and the pressure is too high, which is easy to break the saw blade.
(4) drilling
When drilling on a drilling machine, the rotary motion of the drill bit is the main motion, and the axial motion of the drill bit is the feed motion. When drilling, first draw the cross center line of the hole position at the drilling position, and punch the central sample hole. It is required that the drilling hole is small and the center of the sample hole coincides with the cross intersection. When tripping out, first make a small hole in the hole, observe whether the hole position is correct, and constantly correct it so that the shallow hole is coaxial with the scribing circle. When drilling small diameter holes or deep holes, when cutting is blocked, the feed speed will twist the drill bit. When the drilling hole is about to penetrate, the feed force must be reduced to prevent the drill bit from breaking due to sudden excessive feed, increase the cutting resistance, or cause an accident when the workpiece rotates with the drill bit. In order to cool the drill bit, reduce the friction between the drill bit and the hole, improve the life of the small drill bit and improve the quality of the empty surface, enough cutting fluid should be added when drilling.
Precautions:
1 Strictly abide by the operating rules of drilling rig, and it is forbidden to wear gloves.
When testing is needed during drilling, it must be stopped before testing.
3 When drilling, the handle end of the flat-nose pliers should be placed in the left direction of the drill floor to prevent the flat-nose pliers from falling to the ground and hurting people due to excessive torque.
4 when drilling a large hole, first use a small drill to drill the hole, and then use a big drill to enlarge the hole.
(5) worker thread
Precautions for power line:
Bevel the bottom hole orifice before 1 thread.
2 The clamping position of the workpiece should be smooth, so that the center line of the screw hole is in a vertical or horizontal position.
3 When the tap cuts into 1~2 turns, check and correct the vertical position of the tap in time.
When the hole is blocked, it is necessary to exit the tap frequently to discharge the iron chips in the hole, otherwise the tap will break due to the iron chips blockage or fail to meet the requirements of thread depth.
Common measuring tools for assembly and their assembly drawings
(1) measuring tools: commonly used measuring tools mainly include vernier measuring tools and dial indicators. Vernier measuring tools mainly include vernier calipers. It is impossible to assemble without vernier caliper, which is very important in product size and tolerance. Vernier caliper can measure length, thickness, outer diameter, inner diameter, hole depth, center distance and so on. Vernier calipers are divided into 0' 05 mm and 0' 02 mm vernier calipers, and their scoring principles are basically the same, such as 0. Take the marking principle of 02mm vernier caliper as an example: the length of each square of ruler body is 1MM, and the total length is 49mm, which is divided into 50 squares, and the length of each square of side vernier is 49/50=0. 98mm, the length difference between the ruler 1 and the cursor 1 is 1-0. 98=0。 02 mm, its accuracy is 0. 02mm. Reading method of vernier caliper: First read the integer at the edge of the zero line of the travel scale, and then see which line of the travel scale is aligned with a moment line of the scale from the zero line. The opportunity of the number and accuracy of the vernier line is the decimal part of 1mm, and finally the whole millimeter is added to the decimal to get the measured actual size.
Vernier caliper is an indispensable part in production, so we must pay attention to its accuracy. When measuring, the burr of the workpiece should be removed to avoid scratching the caliper. Put it in the designated position after use, handle it with care, and don't put it with the workpiece. When it is not used for a long time, we need to oil it to avoid slipping.
(2) Assembly drawing
Assembly drawing is a reflection of the designer's intention in mechanical design and an important technical basis for mechanical design and manufacturing. Assembly drawing is to express the working principle of machine or parts, the assembly relationship between parts, the main structural shapes of parts, and the dimensions and technical requirements required for assembly, inspection and installation. Therefore, when assembling, be sure to understand the performance dimensions and assembly dimensions in the drawings. Installation dimensions and overall dimensions.
However, the method steps of assembly drawing are as follows:
1 Look at the title bar first and get a glimpse of the parts.
Look at the title bar to know the name, material, quantity ratio, etc. In order to have a general understanding of the function of the parts. For unfamiliar and complicated assembly drawings, it is usually necessary to consult relevant technical data. For example, the assembly drawing of the parts where the parts are located, the related drawings of other parts and their technical specifications, etc. , so as to understand the function, structural characteristics, design requirements and ghost requirements of parts in machines or parts. Create conditions for looking at pictures.
2. Analyze the research viewpoint and clearly express the purpose.
Look at the front view, top view, left view, partial view, sectional view, etc. So as to understand the relationship between ideas and their expression purposes.
3 Analyze the view deeply and imagine the shape of the structure
Analyze all sizes and find out the size requirements.
According to the structural characteristics, design and manufacturing process requirements of parts, find out the size benchmark, analyze the design benchmark and process benchmark, and clarify the main forms of size categories. Analyze whether the functional dimensions that affect the performance are reasonable, whether the dimensions required for marking the structure meet the requirements, and whether other dimensions meet the process requirements.
5. Analyze technical requirements and fully understand the whole picture.
This paper mainly analyzes the requirements of surface roughness, dimensional tolerance and form and position tolerance of parts. First of all, it is necessary to understand the machining accuracy requirements of the mating surface or the main machining surface, understand the code meaning, then analyze the corresponding requirements of other machined surfaces and non-machined surfaces, understand the machining characteristics and functional requirements of parts, and then understand and analyze other technical requirements such as material heat treatment, surface treatment or modification, inspection and so on.
To sum up, fitters should not only pay attention to marking and filing in processing. Drilling, sawing, etc. It is not enough to understand the assembly drawing, improve labor production efficiency, ensure product quality and pay attention to safety production. We must constantly sum up and refine ourselves in the actual practice and production process, so as to process mechanical products that are beneficial to the efficiency of the factory in the future and not be eliminated by society.