There is no end to learning the skills of a trick, and the most ordinary trick does not require high skills. It can be divided into 5 types of tricks, which are the most common in society today.
1. General mechanical tower
It’s simple and easy to learn. It is better to find a lathe machining department than to learn it at school.
2. Mold turning, especially precision plastic mold turning
The requirements for cutting tools are strict and precise. The finish of the car should be good and easy to polish to a mirror effect. You need to have a 4 prong plastic mold base. Typically, several models are added together to the car. of plastic mold wires! The difficulty is higher!
3. Tool turning
Processing tool shanks of reamers, drills, alloy cutting heads and other cutting tools. This type of filming is the simplest, easiest and most tiring. It is usually produced in large quantities. The most commonly used are double center points, turning cone and flow modulus. This is the quickest and easiest way to reduce tool wear to a minimum, since the hardness of this type of turning product is high. no better than your white knife. How much lower is the steel knife! How well you sharpen your alloy knife will completely affect your results!
4. Large equipment tower
This type of car operator must have experienced skills, and young people basically dare not drive! Learn more when using a vertical car. For example: when rotating a crankshaft, you need to read the drawing n times to determine which part should be turned first and which part should be turned last, whether it is the amount of grinding, or whether it must be machined directly to size, and whether the threads are forward or backward.
5. CNC lathe
This type of tour is the simplest but also the most difficult. First of all, you must be able to read the drawings, the program, the conversion formulas and the application of the tools! As long as you master the theory of lathe and have some knowledge of mathematics, mechanics and CAD, you can learn it quickly.
Let’s talk about 27 tips from practical tour experience
1. Problems that need to be paid attention to when rotating thin shafts at high speed
“Rooks are afraid of tower rods.” This statement reflects the difficulty of spinning thin rods. Due to the characteristics and technical requirements of thin shafts, defects such as vibration, multiple edges, bamboo joints, poor cylindricity and bending are likely to occur during high-speed turning. If you want to drive it smoothly, you must pay full attention to the problems encountered in the process.
(1) Adjustment of the machine tool. The line connecting the center lines of the lathe spindle and tailstock should be parallel to the top, bottom, left and right of the large guide rail of the lathe, and the tolerance should be less than 0.02mm .
(2) Installation of the part. When installing, try not to position too much. When tightening one end with a chuck, do not exceed 10mm.
(3) Tools. Use an offset tool with Κr=75°~90° and pay attention to the secondary draft angle α′0≤4°~6°, which should not be too large. When the tool is installed, it should be slightly above center.
(4) The tool holder must be cut after installation. The cutting method can be grinding, boring, reaming and other methods, so that the arc surface R in contact with the tool holder claw and the workpiece is ≥ the radius of the part and must not be smaller than the radius of the part to prevent the appearance of polygonal edges. When adjusting the tool holder claws, just make sure the claws are in contact with the workpiece. Do not use force to avoid bamboo knots.
(5) Auxiliary support. When the aspect ratio of the workpiece is greater than 40, auxiliary supports should be added during the turning process to prevent the workpiece from vibrating or bending due to centrifugal force. During the cutting process, pay attention to the tip adjustment. It is appropriate to simply cover the part, not too tight, and adjust it at any time to avoid thermal expansion, deformation and bending of the part.
2. Points to pay attention to when turning thin rods with reverse cutting tools
There are many ways to turn thin rods. Generally, the tool holder is used for forward or reverse turning. However, reverse tool turning has many advantages over forward tool turning and is mainly used.
Two problems tend to occur when filming. One is the polygonal shape, which is mainly caused by the large back angle of the tool, which does not match the R of the tool holder claw and the diameter of the workpiece; the other is the bamboo problem. It involves following the knife holder to the mouth of the shelf, then placing and moving the knife. When the cutting surface is reached, the cutting depth increases from minimal to sudden, which causes the cutting force to change outward and the diameter suddenly becomes larger. As the tool holder moves to a larger diameter, the diameter of the cut increases. even smaller and cycle like this to give the piece a bamboo shape.
In order to avoid the formation of a bamboo shape, when the frame mouth in section B is machined, carefully follow the knife holder, and then move the knife back after aligning the knife. When the tip of the knife is close to point A, use it. handle of the center carriage, then cut deeper (0.04～0.08)mm, but it should be controlled flexibly according to the cutting depth.
3. Rolling straightening method
In mechanical processing, rolling processing is often used to improve the surface hardness, fatigue resistance and wear resistance of the workpiece, reduce the surface roughness of the workpiece, and extend the service life of the workpiece. the room. At the same time, the plastic deformation of metal under the action of external force during the rolling process can also be used to change the internal stress to straighten shafts and rods with good rigidity.
During the part rolling process, the rolled part bends due to the uneven hardness of the surface layer under the action of external force. The high position of the curved rotation center bears strong rolling pressure and produces significant plastic deformation, which further increases the bending degree of the workpiece. This phenomenon is more marked when using rigid rolling tools.
The rolling and straightening method is to check the workpiece for runout after rolling it for the first time, mark the recess, and use a four-claw chuck to adjust the workpiece recess to the height of the center of rotation of the machine tool. , in proportion to the bending size of the workpiece, roll for the second time, then use a dial indicator and adjust the claws of the four-jaw chuck to correct the workpiece. Then use a dial indicator to check the bending situation. If it is still bent, use the method above to adjust the part and roll for the third time until the required straightness of the part is achieved. The length of the knife movement after the second time should be based on the specific situation. It is not necessary to cover the entire distance and the reverse motion of the knife should be used.
Rolling straightening is usually carried out during the part rolling process. Not only does it not damage the surface of the workpiece, it can also roll the outer surface of the workpiece evenly without causing dead bends and is easy to use.
4. Screw extrusion straightening method
For screws with larger diameters, longer lengths and multiple bends, extrusion straightening works well.
(1) Operating principle. A straightening tool is used to press the bottom surface of the screw under the action of external force, causing plastic deformation on the surface and extending axially, changing the internal stress state of the screw and making it RIGHT.
(2) Straightening method. First, measure the bending position and direction of the screw on the lathe or platform, then move the curved concave side up and the convex side down to contact the support plate metallic. In the range of the recess (200~300)mm, use a special flat shovel and hand hammer to hit the bottom of the screw teeth to deform the metal with a small diameter of the screw to achieve the recovery objective. During the whole straightening process, the bending state is detected, and the flat shovel is hit and pressed alternately until the screw is straightened. This method is simple and easy to implement. It is not only suitable for large and small screws, but also for straightening shaft blanks. It is not easy to recover after straightening.
(3) Issues to note. The size R of the special flat shovel used for straightening should be greater than half of the thread bottom diameter, b is smaller than the thread bottom width, and α is smaller than the thread angle; the workpiece must be ground in an arc; after straightening, use a file to smooth the pressed bottom of the tooth.
5. Processing of rubber threads
Since the hardness of rubber is very low, its modulus of elasticity is only 2.35 N, which is equivalent to 1/85,000 of carbon steel. It is easily deformed under the action of external forces and is difficult to cut. In particular, it is more difficult to process some special-shaped wires.
In order to process rubber threads, a grinding head capable of arbitrarily adjusting the helix angle is installed on the lathe, or when the thread accuracy is not high, a pneumatic grinding head can be used to the place. The grinding wheel uses white corundum grinding wheel with a diameter of Φ60mm~Φ80mm and a grain size of 60#~100#. After the wheel is installed, use a diamond pen to cut the shape of the wheel. The shape of the grinding wheel is the normal shape of the thread cross section.
The thread is small and has a lathe nameplate, which can be obtained by directly turning the lathe handle. When the turn does not appear on the nameplate, the required sprung wheels must be calculated. Generally, you can consult the manual or use calculation methods to find and make the required sprung wheels.
Generally, when the thread feed is greater than 300mm, the spindle speed should be reduced to avoid affecting the thread grinding quality due to the high spindle speed, and also making the operation strained or damage the parts of the power supply box. Deceleration methods include: changing the diameter of active and passive pulleys; adding a reducer to the outside of the lathe.
The splitting method is the same as the multi-start thread rotation method.
Grinding rubber wires on a lathe is a high-efficiency and high-quality processing technology. The grinding methods are successively used to process single-head and multi-head rubber wires with a feed of (1.5~1280)mm, and their quality meets the requirements. .
6. Step-by-step deep hole turning method
When turning a hole with an aspect ratio greater than 4 on a lathe, due to the poor rigidity of the tool holder, the tool holder vibrates during cutting, which affects the cutting efficiency and the quality of the machined surface, making turning difficult. Especially when the hole diameter is large, the hole is deep and there are steps, processing is more difficult due to the influence of the rigidity of the tool holder and machine tool. In order to improve the quality and processing efficiency of parts, special tooling is designed and manufactured for turning deep holes, and the effect is very good.
First, install the workpiece on the lathe with a chuck and a center frame, use an inner hole cutter to process the short holes at both ends of the workpiece, and equip each with a sleeve and a tool holder special. When turning a long hole in the middle, first insert the support sleeve at the left end into the hole of the workpiece, then install the workpiece on the lathe, adjust the extended length of the tool head on the tool holder and install the holder. sleeve at the left end into the inner hole of the workpiece, use the tool wedge to adjust the height of the tool bar, and fix the tool bar on the square tool table of the lathe so that the bar d The tools can slide freely in the sleeve, then the workpiece can be rotated and the tool can be cut to the longitudinal depth of the workpiece. When the workpiece has finished rotating, move the large carriage to the opposite direction and remove it from the workpiece with the support sleeve and tool bar at the right end, then the workpiece can be unloaded. When processing the second workpiece, first install the left end support sleeve, tighten the workpiece, then extend the toolbar into the left end support sleeve of the workpiece, install the support sleeve d right end, then start turning the second piece.
Tooling Features: Support sleeves are used at both ends to support the cutter shank, which greatly increases the rigidity of the cutter shank, making cutting without vibration and ensuring the roughness of the machined surface. supports the cutting rod to rotate, ensuring smoothness between holes. Easy-to-use position accuracy and efficiency is more than 5 times higher than the traditional hole expansion method.
7. How to adjust the center frame when turning large hollow parts
When turning the inner hole and end face of a hollow workpiece of relatively large length and diameter, a center frame is required. If the center frame is not adjusted well and the center line of the workpiece axis does not coincide with the center line of the machine tool spindle, errors in end face depression, Bulging and tapering of the hole will occur during processing. In severe cases, the workpiece may come out of the chuck, causing an accident.
When installing this type of part, a three-jaw chuck or four-jaw chuck is used on one end of the part and the other end is placed on the center frame. Then insert a piece of wood into the hole of the part or glue a piece of paper with butter to the end face of the part. Place the tip of the tailstock against the wooden board or paper. Use a lower spindle speed to rotate the part. room for a week or two. At this time, a circle is drawn by the tip on the board or paper, and then the three supports of the central frame are adjusted so that the center of the circle is aligned with the tip of the tip. . This essentially aligns the centerline of the workpiece with the spindle axis of the machine tool. After semi-finishing, if the end face flatness and hole cylindricity are measured to be out of tolerance, make slight adjustments to the three middle frame supports to eliminate them.
8. Cleverly remove the center drill tip which is broken in the center hole.
When drilling the center hole, due to the inconsistency between the center of the lathe tailstock and the rotation center of the workpiece, excessive force, high plasticity of the workpiece material and clogging chips, the center drill often breaks in the center hole and is difficult to remove.
If the center hole enlargement method is adopted, the center hole will change its original size and the quality requirements will not be met. At this point, simply use a piece of sharpened steel wire, insert the tip into the chip groove of the drill tip in the center hole, turn it a few times and when the drill tip moves, use a magnet or a magnetic counter base to suck it up and snap it into the center hole. The tip of the center drill inside is removed.
9. How to eliminate defects when turning thin shafts
(1) Belly shape. That is to say, after turning, the diameter of the workpiece is small at both ends and large in the middle. The reason for this defect is that the slender shaft has poor rigidity, the tool holder support claws are not in solid contact with the workpiece surface, and wear creates a gap when turning toward the middle part, due to the radial force. the turning tool The rotation center of the workpiece is pressed to the right side of the spindle rotation center, which reduces the cutting depth. However, the rigidity of both ends of the workpiece is better, and the cutting depth basically does not change. The thin stem becomes domed due to the “knife flex” produced in the middle.
elimination method. When following the tool holder claws, make sure the surface of the claws is in solid contact with the workpiece surface without any gaps. The main deflection angle of the turning tool should be chosen between 75° and 90° to reduce the radial force. For the tool holder, it is advisable to select a cast iron offering better wear resistance.
(2) Bamboo shape. The shape resembles a bamboo joint, and its pitch is approximately equal to the distance between the supporting claw of the tool holder and the tip of the turning tool, and it appears in cycles. The reason for this defect is that because the gap between the large carriage and the middle carriage of the lathe is too large, the centrifugal force caused by the bending and rotating of the blank and the “knife yielding” when the tool is connected to the lathe. base of the tool holder support, causing the The diameter of the turned section is slightly larger than the reference section. Continue to rotate with the tool holder, and the claw of the tool holder holder contacts the larger diameter section of the workpiece, causing the center of rotation of the workpiece to be pressed toward the side of the workpiece. the turning tool and the diameter of the turned part decreases. In this way, the tool holder cyclically presses on different diameters of the workpiece, causing the workpiece to leave and approach the turning tool, forming a regular bamboo shape. Additionally, when the tool holder claws are used during tool movement, excessive force is applied, resulting in pressure from the center of rotation of the workpiece toward the turning tool, reducing the diameter of the turning tool if the tool continues to move. , and this cycle occurs, bamboo joints will also form.
elimination method. Adjust the clearance between different parts of the machine tool to improve the rigidity of the machine tool. When following the claw of the tool holder, the surface of the claw should be in solid contact with the workpiece without using too much force. Add more cutting depth (0.05~0.1)mm at the cutting point to eliminate the “knife” phenomenon when cutting. The size of cutting depth should be controlled flexibly by mastering the rules of the machine tool.
10. Reverse knurling
In traditional forward-spin knurling, chips easily seep between the workpiece and the knurl during the rolling process, causing excessive stress on the workpiece and resulting in random patterns and ghosting. If you reverse the pin, you can effectively avoid the disadvantages mentioned above and roll out patterns with clear lines.
11. Methods to prevent center drill bit from breaking when drilling small center holes
When drilling a center hole with a diameter of less than 1.5 mm on a lathe, the center drill bit can easily break. In addition to being careful and diligent in removing chips when drilling, do not lock the tailstock when drilling and allow friction between the weight of the tailstock and the guide rail of the machine tool carry out the drilling. When the drilling resistance is too great, the tailstock moves back on its own, thus protecting the center drill bit.
12. Set of small eccentric parts
Using a sleeve to clamp the workpiece eccentrically, the clamping efficiency is 6-8 times that of a four-jaw chuck.
Knowing the eccentricity e and the outer diameter of the workpiece Φ2, the inner diameter of the clamping sleeve Φ1 can be found, Φ1 = 2e+Φ2. When processing the inner diameter of the fixing sleeve Φ1, be sure to pay attention to the accuracy of the inner hole to avoid affecting the dimensional accuracy of the eccentricity of the workpiece.
13. The axis rotation method
Screw conveyor mechanism is widely used in factories that transport granular materials. When manufacturing the spiral shaft of this mechanism, its spiral blades are welded from steel plates. This type of spiral plate has a high tooth profile, a small bottom diameter, and the outer diameter and the journal must be coaxial. To meet this requirement, the outer diameter of the spiral shaft must be turned with a lathe.
This type of tree is generally long. When machining the outer diameter, due to the large pitch, deep teeth, fine teeth, poor rigidity and intermittent cutting, the teeth vibrate under the impact of cutting, making them unable to cut normally and equally. Damaged knives. In order to solve this problem, the cutting speed, cutting depth and feed must be reduced, which greatly reduces work efficiency.
In order to improve work efficiency and quality, a simple and easy thread turning method is adopted. Hang the hanging wheel according to the pitch of the spiral shaft, and use the large screw to drive the large carriage to carry out turning. Once the first cut is complete, don’t forget the middle cart ladder. After the large carriage returns, use the small tool holder to advance (0.5~0.7)mm, then start the second cut until the outer circle is completed.
The tooth top of the spiral shaft turned by this method is flat, which basically eliminates intermittent cutting, and the processing efficiency is nearly 10 times that before.
14. Processing threads outside the lathe nameplate
Among many mechanical transmissions, the pitch and feed of multi-head worms, multi-head screws, multi-head helical splines, variable feed worms, variable tooth thickness worms double feed, helical gear worms, etc. the lathe nameplate. Difficulties arise during processing. We now introduce a solution to the problem that the required pitch (or feed) cannot be found on the lathe nameplate, which can save you from having to make a hanging wheel.
For example, the worm gear meshing with the helical gear on an imported milling machine has a normal modulus of 3.175 and a circumferential modulus of 3.184. Module 3,184 is not found on a lap. To deal with it, the hanging wheel must be calculated and made. . After calculation and analysis, the modular pitch is converted into metric pitch, i.e. 3.184 × 3.1416 = 10.003 mm, so that it can be processed with a pitch of 1 O mm.
When overhauling and maintaining equipment, the thread pitch is mainly measured in the metric system, so non-standard pitch will appear. In fact, threads are divided into ordinary threads, inch threads, modulus threads, diameter threads and non-standard threads, and their pitches can be converted to each other. For example, 9.4248mm, 12.5664mm, 12.7mm, 25.4mm and 7.9756mm can all be processed to other thread types. The results are P=9.4248 mm and P=12.5664 mm, which are module 3 and module 4, respectively.
Another example is 12.7mm and 25.4mm, which are inch threads with 2 threads/inch and 1 thread/inch respectively. P=7.9756 mm is a diameter pitch thread with DP=10.
15. Tooling for drilling large and long interior tapered holes
When processing an inner taper hole with a larger diameter and longer length on a lathe, if a general turning method is used, due to the poor rigidity of the tool holder, it will vibrate during turning, the cutting quantity will be very small, and it may even be impossible to cut it. Large inner holes or inner tapered holes that meet the requirements have been successfully processed many times.
During processing, one end of the workpiece is clamped by a chuck and the other end is supported by a central frame. Place an anti-center in the spindle hole of the lathe, position one end of the tool bar with a steel ball, and use a connecting sleeve and fixing screws on the other end to fix the tool bar on the tailstock sleeve of the lathe, so that when the workpiece rotates, the toolbar cannot rotate. The cutting head can only slide axially on the cutting support using the key. One end of the wire is fixed on the cutting head and the other end is fixed on the large carriage of the lathe. When the large carriage performs longitudinal cutting, the cutting head is pulled to move axially to complete the feed movement and perform cutting.
Before installing the toolbar, the tailstock of the lathe should be placed in front of the large carriage, so that the large carriage can pull the wire to drive the cutter head to move. The amount of feed can be obtained by adjusting the tool handle. power box. When processing a tapered hole, the tailstock can be shifted so that the tool holder axis and the workpiece axis are offset by an oblique angle in the horizontal direction. When the cutter head returns, simply push the cutter head in by hand.
This tool is used to process large interior holes on a lathe. It is very convenient to use, has a simple structure, and the tool holder has good rigidity.
16. Change the number of teeth of the gear driving the wheel housing and increase the reach of the worm thread.
By increasing the number of teeth of the driving wheel of the C620-1 lathe wheel housing from 32 to 48 teeth, threads of modules not listed on the nameplate can also be processed. If the drive wheel is changed from 32 teeth to 64 teeth, the worm can then rotate without being limited by spindle speed ratio and low speed finishing can be used, which will help improve the surface roughness of the thread .
17. Methods for reducing surface roughness of thin trees (stems)
To reduce the surface roughness of a thin shaft (rod) on a lathe, one is to use single-wheel honing; the other is to use rolling. This is an effective measure of using simple tools and processes on a lathe to solve the problem of low roughness requirements and grinding without a grinder.
After finishing the thin shaft (shank) on the lathe, if the roughness has not reached the drawing requirements, the single wheel lapping method can be used to reprocess the workpiece surface, which can reduce the roughness of the part of Ra6.3 μm. to masonry (1.6～0.2)μm. The angle between the axis of the sharpening wheel and the axis of the lathe spindle is generally 28° to 30°. A large included angle has high efficiency and high roughness, while a small included angle has low efficiency and roughness. The speed of the sharpening wheel is generally (30 ~ 60) m/min, and the feed speed is (0.5 ~ 2) mm/r. Choose a larger value for coarse sharpening. The pressure of the sharpening wheel on the workpiece is (150 ~ 200) N. For workpieces with low rigidity, a tool holder should be used. The grain size of the lapping wheel is generally 100#~180# If the roughness needs to reach Ra0.2, the grain size of the lapping wheel should be W40~W280. The lubricant used for break-in should be kerosene or diesel with 5.%~10% oleic acid added. When there are no conditions, ordinary emulsion can also be used to clean and lubricate the sharpening process.
Rolling processing of thin shafts (rods) can effectively reduce surface roughness while improving surface hardness and wear resistance. Due to the low rigidity of the part, a heel tool holder should be used during rolling. The method used is the same as that of rough turning of the slender shaft, that is, the heel tool holder is placed in front of the rolling tool. to prevent the claws of the heel tool holder from damaging the workpiece surface. Rigid or flexible rolling tools can roll long, thin shafts (rods). The number of rolling operations is usually no more than two. The rolling speed is (20~30) m/min and the feeding quantity is (0.1~0.2) mm/r. It is lubricated with engine oil or emulsion.
18. Method of correcting the workpiece with a copper rod
Part correction, also called alignment, is a method of checking whether the part is installed in the correct position before turning it. The purpose of the correction is to ensure that the stock allowance of the part is basically consistent during rough turning; during semi-finishing and finishing turning, it is to ensure that the relative position of the surface to be machined and the machined surface meets the requirements. Fast and correct calibration is an important measure to ensure product quality and reduce auxiliary time.
The method of using copper rods to correct the workpiece is a quick correction method which is carried out after roughly turning the outer circle and end face of the workpiece, and then installing the workpiece. Fix a copper rod or aluminum rod on the square tool table of the lathe, lightly clamp the workpiece on the three-jaw chuck, start the lathe and rotate it at about 100 rpm, so that the copper rod contacts the end face or exterior. circle the part and shake it by hand. The carriage applies a certain pressure until the workpiece surface is in full contact with the copper rod, then slowly separates the copper rod from the workpiece, then stops the machine to clamp the workpiece and the workpiece to be machined is corrected.
This correction method is fast and accurate and can achieve a certain degree of precision. If the workpiece is clamped reasonably (less than 10mm), the workpiece surface is smooth, and generally the radial runout of shafts and end face runout of disc workpieces are not greater than 0 .02mm.
19. Method of straightening thin rods on a lathe
Thin rods must be straightened before turning, otherwise the machining allowance will be uneven and the turning will not be round, or the bending eccentricity will increase the curvature of the rod and make it impossible to rotate. To straighten a thin rod on a lathe, the following method can be used.
(1) Use the hammering method. First, clamp one end of the thin rod about 10mm with a three-jaw chuck and support it at the top. Run the work at low speed and after drawing high spots on the workpiece with chalk, stop. Hold a concave iron block in your left hand, so that the concave surface is against the opposite side of the high point of the workpiece, and use a hand hammer in your right hand to strike the high point of the workpiece. The magnitude of the striking force is directly proportional to the bending of the part. Repeat this several times and the piece will be straightened. This method is suitable when the stem is thin and long.
(2) Use the leverage method. Once the thin rod is installed on the lathe, drive the machine to turn the workpiece. Use a 300mm long wooden stick to rest on the central cart and square tool table. Shake the center cart to press the wooden stick against the curved part of. the workpiece. Continue to move the center carriage and follow the top of the tailstock to prevent the workpiece from falling. Wait for the workpiece to continue rotating for a few seconds, then slowly remove the center slide and loosen the top of the tailstock appropriately. to see if the part is straightened. If it is still bent, continue with the method above until it is straightened. This method is suitable when the piece is short.
(3) Use counterattack. When the thin shank is long and has a relatively large diameter, first drill the center holes at both ends, and then use the top of the spindle and the top of the lathe tailstock to lift it. Next, turn the piece by hand to find the high points of the piece and mark them with chalk. At this time, use a relatively large iron block or wooden block about 25mm thick and 40mm wide, wider and longer than the large guide rail of the lathe, and place it horizontally on the large guide rail. Place a head on it that is not 60.° sharp but V-shaped or The arc-shaped concave threaded jack is supported at the high point of the workpiece deformation. Use a little force to support the coin with your left hand and strike the low point of the coin’s curvature. with the round head of the hammer with your right hand. The number of blows, force and length of the part are proportional to the size of the fold. The piece thus straightened is not easy to recover after having been folded.
In addition to the above-mentioned method to straighten the thin rod on the lathe, you can also use visual inspection outside the machine tool and visual inspection on the platform to straighten it using the method above.
20. Turning tool for turning the inner spherical surface in deep holes
When turning materials such as plastic, nylon and organic glass, the connection point between the inner cylindrical surface and the inner spherical surface in the deep hole must be very smooth and without steps, which makes processing difficult. For this reason, turning of the inner hole and the inner spherical surface must be performed in a single finishing pass.
In order to process the inner hole of this part, first make an inner hole turning tool. The blade material is tool steel or alloy tool steel, and the quenching is HRC (60~62). Production method: first turn a knife blank on a lathe, heat treatment and quenching, grind the two end surfaces, install the inner hole of the blade with the chuck, grind the outer circle or tool for grinding the outer circle and back angle as required. , then grind off the excess according to the shape of the blade. Part is ground to prevent the rear face from getting in the way when turning the holes and making rotation impossible. Then fix the blade on the tool holder with screws so that the cutting surface of the blade is close to the center of the tool holder to avoid the lower part of the tool holder from getting in the way. This can also hinder the cross section. the tool holder larger, which is beneficial to improve the rigidity of the tool holder.
When turning the inner hole, first use a drill bit to drill the hole, and then use an inner hole cutter to roughen the inner hole. When finishing turning, the tool is installed on the square tool table of the lathe, and the edge of the blade and the rotating center of the workpiece are placed at the same height. First use this knife to semi-finish the inner hole, and the depth of the hole basically meets the requirements. After completing the cylindrical part of the inner hole, the inner spherical surface located deep inside the hole is also turned in the same tool passage. At this point, all interior holes are completed. This type of tool and operation method makes the inner hole and the inner spherical surface have no contact marks and are very smooth.
21. Turning of plane threads
The so-called plane thread is a thread processed on the end face of a cylinder or disc.
When turning plane threads on an ordinary lathe, a light rod drive is usually used to turn the intermediate carriage screw and drive the lathe intermediate carriage to move sideways to turn. This requires that each time the part rotates, the central carriage moves the part sideways one step.
When the pitch requirements of the workpiece are not strict, the pitch of the plane thread of the workpiece can be divided by the multiple of the increase in the pitch of the lathe (for example, the C620-1 lathe can increase the pitch by 2 , 8 or 32 times). Use the resulting quotient to select the lathe nameplate to get closer to horizontal. advance and turn the handle of the tool feed box as needed, then turn the pitch increase handle on the spindle box to the pitch increase position, and turn the gear change handle on the spindle box to the required position, install the tool and can perform flat thread turning.
When the workpiece pitch requirements are strict, the hanging wheels of the wheel box need to be replaced. Before calculating the hanging wheel, follow the above method to select an approximate amount of lateral movement of the tool, adjust the feed box, increase the pitch and variable speed handle, and perform lateral movement of the tool. tool. Then use the whole number of the spindle (more than 5 revolutions) to divide the distance traveled by the cross slide, and the resulting quotient is the actual pitch of the revolution. Under normal circumstances, the pitch will not be equal to the required pitch of the workpiece, so it is necessary to calculate and replace the hanging wheels of the wheel box.
When turning, it is best to use a flexible tool holder. The geometric parameters of the tool head are the same as those for turning cylindrical threads. However, the secondary clearance angle on the inner face of the tool head must be ground with a double. clearance angle to prevent this part from getting in the way when turning. The lathe spindle is used to rotate the tool forward and backward and to return the tool. There are two ways to eat the knife: one is to use the small tool holder of the lathe to engage and withdraw the knife, and use a small millimeter hoop to count, the other is to install a magnetic counter holder and a dial indicator; the large guide rail in front of the large carriage to control the large tool. The position of the carriage and the degree of engagement of the knife, and use a large carriage to engage and retract the knife.
In the process of turning plane threads, in addition to square threads, turning threads of other tooth types also requires “cutting” like turning cylindrical threads to finely turn both sides of the tooth type. There are two methods to “catch the knife”: one is to use a large cart to grab and remove the knife, rotate the small knife holder 90° counterclockwise, and fix it, and simply shake the handle of the small knife holder when “catching the knife”: the other is to use a large cart or a small knife holder allowing you to take the knife in and out. When you want to “catch the knife” the tool”, put the tool head outside the workpiece, stop the spindle during the movement of the tool, but it should not move back. At this time, the worm handle will fall off and the carriage handle. center must be turned to “catch the tool”, then raise the worm handle. To use this method to “drive the cutter”, the gap in the drive chain must be eliminated, i.e. -say in which direction the cutter must be “cut”, the central carriage must move the cutter in the same direction. After “squeezing the knife”, the cutting head is gradually cut into the workpiece.
22. What are the tips for sharpening high speed steel trapezoidal thread turning tools?
When it comes to threading on the lathe, the main thing is to use your hands more often and learn more from the old masters, so you can progress quickly.
A thread is a continuous projection with a prescribed profile formed along a spiral line on a cylindrical or conical surface. Threads are widely used in various machines. For example, four screws are used to tighten the turning tool on the square tool holder of the lathe. Threads are used to transmit power between the lathe screw and the opening and closing nut. There are many ways to process threads, and thread turning is generally used in general machining (one of the basic skills of a lathe).
When processing threads on a horizontal lathe, the movement relationship between the workpiece and the tool must be ensured, that is, the tool moves uniformly by one step (or feed) every time the spindle turns (the part turns once). Their kinematic relationship is guaranteed as follows: the spindle drives the part to rotate together. The spindle movement is transmitted to the feed box through the suspended wheel box. The feed box is transmitted to the screw after the gear shift. The nut cooperates to drive the tool holder and the turning tool to move linearly, so that the rotation of the workpiece and the movement of the tool are achieved by the driving of the spindle, thereby ensuring a relationship strict movement between the part and the tool.
During the actual turning of threads, due to various reasons, problems occur in a certain connection of the movement between the spindle and the tool, causing failures in thread turning and affecting normal production. This should be resolved in time.
23. The tooth profile angle is incorrect
1) Tool tip angle is incorrect
When sharpening turning tools, the angle of the tool tip is incorrect, that is, the angle between the projection of the two cutting edges of the turning tool on the base surface is not consistent with the thread profile angle, resulting in an incorrect thread angle. Solution: When sharpening turning tools, you must use an angle ruler or jig to detect and obtain the correct tooth profile angle. The method is: place the template or angle ruler parallel to the front of the turning tool, and then use light transmission. method to check. Commonly used metric thread profile angles: 60° for triangular threads, 30° for trapezoidal threads, and 40° for worm screws.
2) Radial rake angle is not corrected
In order to facilitate the removal of chips from the turning tool, reduce the surface roughness and reduce the built-up edge phenomenon, the radial rake angle is often ground, which makes the cutting of both sides of the turning tool do not coincide with that of the turning tool. axial direction of the part, which results in the turning of the threads of the part. The profile angle is larger than the tip angle of the turning tool. The larger the radial rake angle, the larger the tooth profile angle error. At the same time, the profile of the turned thread is not a straight line in the axial section, but a curve which affects the matching quality of the thread pair. Solution: When sharpening a thread turning tool with a large radial cutting angle and turning the thread, the angle of the tool tip should be corrected by the angle between the two edges of the turning tool, especially for high precision machining threads. The correction calculation method. East:
tanεr=cosrp·tanα
In the formula, εr is the angle between the two cutting edges of the turning tool; rp is the radial rake angle; α is the angle of the tooth profile;
3) The tooth profile angle is too large when cutting high speed steel.
When cutting threads at high speed, due to the compressive force of the turning tool on the workpiece, extrusion deformation will occur, which will enlarge the profile of the processed tooth and swell the workpiece. Therefore, when sharpening the turning tool, the angle between the two occurs. both edges should be trimmed appropriately. Small 30′. Additionally, the large diameter of the workpiece before turning the external threads is usually less than the nominal size (about 0.13p).
4) The turning tool is installed incorrectly
Improper installation of the turning tool means that the symmetrical center line of the two cutting edges of the turning tool is not perpendicular to the workpiece axis, resulting in tilting of the profile angle of the treated tooth (commonly called inverted tooth).
Solution: Use an angle ruler or jig to install the turning tool so that the center axis of symmetry is perpendicular to the workpiece axis and the tip of the tool is at the same height as the center of the room.
5) Tool wear
After the tool is worn out, it is not sharpened in time, causing the two sides of the processed tooth profile angle to be not straight lines but curves or “bad teeth”.
Solution: Choose the cutting amount reasonably and sharpen the turning tool in time after it wears out.
6) The pitch (or lead) is incorrect
The total length of wire A is incorrect. The reason why the overall thread length is incorrect is that the calculation or assembly of the replacement gear is wrong, and the position of the feed box handle and slide box is incorrect. You can recheck the position of the feed box handle or check the hanging wheel. .
Wire B is partially incorrect. The reason for the partially incorrect thread is that the lathe screw and spindle move too much, the slide housing handwheel turns unbalanced, and the gap between the opening and closing nuts is too large.
Solution: If caused by axial movement of the screw, the adjusting round nut at the connection between the lathe screw and the feed box can be adjusted to eliminate the axial play of the thrust ball bearing at the connection level if it is caused by; axial movement of the spindle Caused by the movement, the adjusting nut can be adjusted after the spindle to eliminate thrust The axial play of the force ball bearing; if it is caused by poor meshing caused by the non-axial opening and closing nut of the sliding housing and the screw, the opening and closing nut can be cut off and the clearance of the nut d Adjusted opening and closing. ; If the sliding box is unbalanced in rotation, the steering wheel of the sliding box can be removed to clear it from the rotating shaft and rotate evenly.
C During the turning process, the opening and closing nut automatically lifts, making the thread pitch incorrect.
Solution: Adjust the insert of the opening and closing nut to reduce the gap appropriately, control the lifting of the opening and closing nut during transmission, or hang a heavy object on the handle of the opening and closing nut to prevent it from being lifted halfway.
24. Large surface roughness value
Reasons for high surface roughness values:
(1) A built-up edge occurs on the tip of the tool;
(2) The tool holder is not rigid enough and produces vibrations when cutting;
(3) The radial rake angle of the turning tool is too large, and the gap between the screw nut in the central sliding plate is too large, causing the tool to stick;
(4) When cutting threads in high-speed steel, the cutting thickness is too small or the chips are discharged in an oblique direction and the surface of the processed tooth flanks is roughened;
(5) The workpiece has poor rigidity and the cutting quantity is too large;
(6) The surface of the turning tool is rough.
Solution:
(1) If it is caused by built-up edge, the cutting speed should be adjusted appropriately to avoid the range in which built-up edge occurs (5 ~ 80 m/min when cutting with metal turning tools). high speed steel, cutting); the speed should be reduced appropriately and the cutting speed should be selected correctly; When turning threads with carbide, the cutting speed should be increased appropriately.
(2) Increase the cross section of the tool holder and reduce the extension length of the tool holder to increase the rigidity of the turning tool and avoid vibration.
(3) Reduce the radial cutting angle of the turning tool and adjust the central sliding plate nut to reduce the gap as much as possible.
(4) When cutting threads in high-speed steel, the chip thickness of the last cut should generally be greater than 0.1mm, and the chips should be discharged along the vertical axis to prevent chips from coming into contact with the machined surface.
(5) Choose a reasonable cutting amount.
(6) The surface roughness of the tool cutting edge is 2-3 degrees lower than the roughness of the thread processing surface. After sharpening the turning tool with the grindstone, it must be ground with a whetstone.
25. Stray teeth
The reason for the untidy teeth is that when the screw rotates once, the workpiece does not rotate an integer multiple of the rotation of the screw, that is, the rotation of the workpiece is not an integer multiple of the rotation of the screw.
A commonly used method to prevent tooth decay is to first turn the turning tool in reverse, that is, at the end in one stroke, do not lift the nut from opening and closing, withdraw the tool radially, reverse the spindle and make the tool return longitudinally, then perform the second step. During the reciprocating process, because the transmission between spindle, screw and tool holder is not separated, the turning tool is still in the original spiral groove and no random teeth will occur. Second, when the longitudinal stroke of the tool feed is completed, the opening and closing nut is lifted from the transmission chain and sent back, and the position of the tool tip is moved, and the tool must be calibrated again.
26. The pitch diameter is incorrect
The reason for the incorrect pitch diameter is that the cutting depth of the turning tool is incorrect. The cutting depth is controlled according to the upper diameter, and the influence of the upper diameter error is ignored, and the measurement is carried out timely; is not performed during the turn. Solution: When you finish filming, check if the dial is loose and use it correctly. The finishing tolerance must be appropriate. Measure the pitch diameter in time. Consider the influence of the larger diameter and adjust the cutting depth.
27. Fold or fold the workpiece
Reasons why the tool gets stuck or bends the workpiece: the tip of the turning tool is lower than the center of the workpiece (machine tool); the cutting angle of the turning tool is too large and the gap between the central slide plate and the screw are large; the rigidity of the part is poor and the cutting quantity is too great. Solution: First of all, when installing the turning tool, the tip of the tool should be aligned with the center of the workpiece or slightly higher. Second, reduce the cutting angle of the turning tool, reduce the radial force, and adjust the gap between the central sliding plate and the screw. Third, choose a reasonable cutting amount according to the rigidity of the workpiece; increase the rigidity of the workpiece and increase the rigidity of the turning tool.
In short, many types of defects occur during thread turning, including reasons of equipment, tools, measurements, operations, etc. When troubleshooting, you need to analyze the specific situation and know the specific conditions through various detection methods and diagnostic means. . influencing factors and adopt effective and reasonable solutions.
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