[Abstract] According to the characteristics of students in technical schools, the practical problems existing in students' production practice are solved, and the accurate positioning method of file handle in the palm is explored. Using thrust points to promote the formation of sawing skills. Teaching students in accordance with their aptitude enables them to master a skill and become useful talents for the four modernizations of society.
[Keywords:] The formation of file handle thrust point saw technology
Filing and sawing are the basic operating skills that locksmith students in technical schools must master. The learning of file saw skills is restricted and influenced by many factors, such as grip, standing posture, body movements, power points and so on. Traditional grip method (such as p35 in locksmith's production practice, Figure 4.2, grip method of large plate file; P59, as shown in Figure 5.2, the holding position of the hand saw slightly deviates from the palm after holding the file handle. When filing, the handle of the file gradually moves backward, and the "grip" becomes "grasp", which leads to insufficient pushing force of the file; The thrust point of holding the saw handle completely is about 30mm higher than the center of the saw blade mounting hole. The high thrust point is easy to cause the saw bow to swing to both sides, which leads to the fracture of the saw blade and the skew of the saw seam.
Based on this, the author discusses how to improve the grip of file and saw combined with years of teaching practice.
A, reasonable reference, improve the file handle grip.
Filing is one of the basic skills that every fitter must master. In the process of learning skills such as sawing, filing and chiseling, many students think that filing skills are easy to master. In fact, the precision of filing plane, parallel plane and vertical plane is very high. To achieve the processing accuracy of filing, we must master solid basic skills, and the grip of the file is the key to the formation of basic skills of filing.
1, the traditional method of grabbing large files and its existing problems
Holding method of large file: hold the file handle with the right hand, with the handle end resting on the palm of the thumb root, the thumb batch resting on the upper part of the file handle, and the rest fingers holding the file handle from bottom to top [see p35, (Figure 4.2)]. This is beyond reproach. But most students think that filing operation skills are easy to master and there is no danger. Therefore, when the practice instructor explains and demonstrates, the students are careless and can't grasp the essentials of holding the handle, resulting in 2/3 students holding the handle slightly out of their palms. When filing, the handle moves backward gradually, and the "grip" becomes "grip" (as shown in figure 1). Because the handle of the file is not supported on the palm of your hand, the pushing force of the file is insufficient, the balance of force cannot be controlled by both hands, and the action is uncoordinated, so the processed surface of the file is uneven.
2, improve the file processing method
In order to solve the problem that students' file handles are prone to tilt, they often put the file handles on the palm of their hands and press them repeatedly, so that the file handles are accurately aligned with the palm of their hands, and various attempts are made to seek accurate positioning. In the attempt, it was found that after hooking the middle finger of the right hand, the gear handle was placed on it, and after grasping the gear handle, the abutting part was closer to the palm. On this basis, the grasping order of each finger is adjusted to make the file handle hold the palm more accurately. In the process of hooking the middle finger of the right hand, it is found that if the ring finger and the little finger are closed, it is consistent with the gun shape of the child's hand when playing. When this method is applied to teaching, the file handle can be accurately positioned on the palm of your hand. The specific method is as follows:
A) The right hand comes out first, as shown in Figure 2(a). If the right hand raises the gun in this position, it is easy to attract students' attention.
B) The right hand is shaped as shown in Figure 2(b), and the right hand is in this position to make the file consistent with the filing direction after being held.
C) Place the file handle at the bend of the middle finger and keep it in the palm position [as shown in Figure 3(a)].
D) Hold the file handle with your thumb. Move the pressing handle with the middle finger slightly loose, and hook the pressing handle with the index finger relative to the thumb, so that the pressing handle abuts against the palm position (as shown in Figure 3(b)). Please note that the file is placed horizontally.
E) In the filed state, the relative position of human body should be adjusted to ensure that I, II and III are in a straight line [as shown in Figure 4 (a) and (b)]. If three o'clock is in a straight line, the direction of document advancement will be fine. Because the file can move in a straight line during the propulsion process, the surface of the file workpiece can meet the flatness requirements and improve the quality of the machined surface.
Through the "game" of image technique, students' thinking can be inspired, students' interest in learning can be stimulated, classroom learning atmosphere can be activated, skills can be improved rapidly, and the surface quality of filing processing can be improved accordingly, forming a virtuous circle, which greatly promotes the formation of filing skills.
Second, skillfully use thrust points to promote the formation of seesaw skills.
Saw seems to be as easy to use as file, but most students are prone to the phenomenon of too fast speed (80 times/minute) and skewed kerf when learning saw. Without studying hard and studying the grip of the saw bow and the position of the power point, it is difficult to turn skills into skills.
Most practice coaches teach "hand saw grip and saw posture, pressure and speed grip" according to p58 figure 5. 1 grip and textbook content. It turns out that the right hand fully holds the saw handle and the left hand gently holds the front end of the saw bow, which plays a key role for students to master the sawing skills. However, if students simply continue to practice according to the traditional sawing method, they will not concentrate on studying the grip and stab points, and their skills will gradually improve. Moreover, due to the limitation of the action points of both hands, it is difficult to form skills, and the quality and flatness of the sawing surface are difficult to meet the accuracy requirements.
When the original right hand holds the saw handle completely, the thrust point acting on the saw handle is about 30mm higher than the center position of the saw blade mounting hole [Figure 5(a)]. Because the stress point is not in a straight line with the saw blade, the high stress point is easy to cause the saw bow to swing to both sides, the saw blade is easy to break, and the saw seam is skewed, which leads to the consumption of the saw blade and the flatness of the saw section, and the machining quality is affected. Except the right hand pricking point (grip posture), the pressing position of the left thumb has a great influence on the downward pressure of the saw bow. If the pressing pressure at the front end is insufficient, it will easily lead to imbalance before and after the push-out, which will lead to a large up-and-down swing during sawing, affecting the movement route of the saw blade and the clarity of saw marks on the section.
Assuming that the center of the mounting hole is a fixed point and the thrust point 1 is 30mm above it, the offset of the saw bow to one side is B (Figure 6). If the point moves down 20mm, when the thrust point 2 is higher than the fixed point 10mm[ (Figure 5 (b)) and the thrust point is close to the center of the saw blade mounting hole, that is, when the thrust point directly acts on the saw blade movement, the offset of the saw bow to one side is B/3. (Note: the thrust point 2 is the limit position for completely grasping the saw handle). In addition, the thumb is hooked, and the saw bow is buckled with the inside of the joint, so that the downward force can be increased by about 1 time. Due to the increase of the downward force at the front end, the imbalance problem caused by the moment of pushing out can be solved. Of course, the body should cooperate to complete the whole sawing action, and pay attention to that the pushing force of the right hand is greater than the downward force of the front end, so that the saw blade can move forward without breaking. In other words, we must master the correct method, study hard, let the movements coordinate naturally, and naturally get the best sawing efficiency.
With the increase of downward pressure at the front end and coordinated movements, the sawing speed will naturally slow down, and people will not be easily tired during operation, which is very conducive to the "protracted war" of sawing. After the improvement, because the reciprocating speed can generally be lower than 40 times/minute, there is more time to pay attention to the position of the saw seam and the drawn processing boundary, thus improving the plane quality of the saw section. Due to the improvement of sawing quality, students feel the joy of skill progress, improve their interest in learning, and shorten the learning time from skill to skill by about 1/3.
To sum up, in the grip method of file handle, because it is entertaining, it stimulates students' interest in learning, mobilizes their initiative in learning, solves the problem that the file handle is opposite to the palm, improves students' enthusiasm in learning, improves the quality of processed surface and promotes the formation of filing skills; In the sawing method, due to the change of the action point of two-handed force, the direction of the right-handed thrust point is close to the forward direction of the saw blade, which reduces the push swing of the saw bow, improves the downward force of the left hand, ensures the balance before and after the push moment, improves the sawing efficiency and the quality of the sawing surface, and shortens the time for transforming skills into skills. The improvement of these two technologies has played a very good role in promoting production practice teaching.