1 Issues to be aware of when turning a slender shaft at high speed

"Lady workers are afraid of the car." This sentence reflects the difficulty of turning slender rods. Due to the characteristics and technical requirements of elongated shafts, vibrations, multiple edges, slubs, cylindricity differences, and bending defects are easily generated during high-speed turning. If you want to smoothly drive it, you must pay full attention to the problems in the process.

(1) Machine tool adjustment. The connection between the centerline of the lathe spindle and the tailstock must be parallel to the upper and lower rails of the lathe, and the allowable difference should be less than 0.02mm.

(2) Workpiece installation. When installing, try not to over-position. When using a chuck to clamp one end, do not exceed 10mm.

(3) Tool. Using Κr = 75 ° ~ 90 ° eccentric knife, pay attention to the auxiliary relief angle α'0 ≤ 4 ° ~ 6 °, should not be large. When installing the tool, it should be slightly higher than the center.

(4) With the tool post, after the installation, the dressing and dressing must be carried out. The method of grinding, reaming, boring, etc. can be used to make the arc surface of the tool holder claw contact with the workpiece R ≥ the workpiece radius, and must not be less than the workpiece Radius to prevent multiple edges. When adjusting the jaws of the tool holder, contact the jaws with the workpiece. Do not use force to prevent the occurrence of slubs.

(5) Auxiliary support. When the length-to-diameter ratio of the workpiece is greater than 40, an auxiliary support shall be added during the turning process to prevent the workpiece from vibrating or bending the workpiece due to centrifugal force. During the cutting process, attention should be paid to the adjustment of the top, and it is advisable to use the workpiece on the rigid top only. It should not be tight and be adjusted at any time so as to prevent the workpiece from thermal deformation and bending.

2 Problems that should be noticed when turning the slender rod

There are many ways to turn an elongate bar, generally using a knife holder for positive or negative cutting. However, anti-cutting turning has many advantages compared to straight turning and is mostly adopted.

There are two problems in turning, one is a multi-prism, which is mainly due to the large tool back angle, which is caused by the mismatch between the R of the tool holder and the diameter of the workpiece; the other is the bamboo problem. It is from the shelf with the knife after the knife, when the knife, knife to the cutting surface, the cutting depth from the minimum to suddenly increase, so that the cutting force changes, the workpiece is produced out of the knife, the diameter suddenly changed When the cutter head is moved to a large diameter, the diameter of the car becomes smaller, and the cycle is repeated so that the machined workpiece has a bamboo shape.

In order to prevent the occurrence of bamboo shape, when the vehicle is in good B-section shelf (Fig. 3-1), carefully follow the knife holder, reverse the knife after the knife, when the knife tip is approaching point A, use the middle plate Handle, then eat deep (0.04 ~ 0.08) mm, but according to the size of cutting depth flexibility.

3 Rolling and straightening method

In mechanical processing, rolling process is often used to improve the surface hardness, fatigue strength and wear resistance of the workpiece, reduce the surface roughness of the workpiece, and prolong the service life of the workpiece. At the same time, it can also be used in the rolling process, the metal plastic deformation under the action of external forces, so that the internal stress changes to straighten the shaft and rod workpieces with better rigidity.

In the process of rolling the workpiece, the workpiece being rolled is bent under the influence of external force due to uneven hardness of the surface layer. The high center of rotation of the bend, the rolling pressure received, and the resulting plastic deformation is also large, so that the degree of bending of the workpiece is even greater. This is especially true when rigid roller tools are used.

The method of rolling and straightening is to inspect the radial runout of the workpiece after the first rolling of the workpiece, mark the recess, and use the four-jaw chuck to adjust the recess of the workpiece to the height of the center of the machine's rotation. , It is proportional to the size of the workpiece bending, and then a second rolling, and then use the dial indicator and adjust the jaws of the four-jaw chuck to correct the workpiece. Then use a dial indicator to check the bending condition. If it is still bent, use the above method to adjust the workpiece and perform the third rolling until it reaches the required straightness of the workpiece. The length of the knife after the second time should be based on the specific circumstances, and it is not necessary to take the full course, and anti-passing knife should be used.

The use of rolling and straightening is generally completed in the process of rolling the workpiece, not only does not damage the surface of the workpiece, but also makes the outer surface of the workpiece more uniform rolling, will not produce dead bends, but also easy to operate.

4 screw extrusion straightening method

For longer diameters and longer lengths, there are also several curved screw rods, and extrusion straightening works well.

(1) Working principle. The straightening tool is used to press the surface of the bottom of the screw under the action of the external force so that the surface of the screw will be plastically deformed, extend axially, change the internal stress state of the screw, and make it straight.

(2) Straightening method. First, on the lathe or on the platform, measure the position and direction of the bending of the screw, and then put the curved recess upwards, and the convex surface faces down to contact with the metal plate, as shown in Figure 3-2(a). Within the range of (200-300) mm in the recess, use the special flat spade shown in Figure 3-2(b) and the hammer with a hand to strike the bottom of the screw to deform the metal of the small diameter of the screw to achieve the aim of straightening. . During the entire straightening process, the bending is detected and the flat shovel is pressed against the stagger until the screw is straightened. This method is simple and easy to use, not only for small and large screws, but also for the straightening of shaft blanks, and it is not easy to recover after straightening.

(3) Problems that should be noted. The size R of the special flat shovel used for straightening shall be greater than half the diameter of the bottom of the screw, b shall be less than the width of the bottom of the tooth, and α shall be less than the angle of the teeth; the R section contacting with the workpiece shall be rounded; after the straightening is completed, Apply a trowel to flatten the bottom of the dentition.

5 Rubber Thread Machining

Because the hardness of rubber is very low, the modulus of elasticity is only 2.35N, which is equivalent to 1/85000 of carbon steel. Under the action of external force, it is easily deformed and difficult to cut. In particular, it is more difficult to cut some special-shaped threads.

In order to solve the processing of rubber threads, a grinding head can be installed on the lathe to adjust the helix angle arbitrarily, or in the case where the accuracy of the thread is not required, the pneumatic grinding head can also be used instead. The grinding wheels use white corundum grinding wheels with diameters of Φ60mm to Φ80mm and grain sizes of 60# to 100#. After the grinding wheel is installed, a diamond pen is used to trim the shape of the grinding wheel. The shape of the grinding wheel is the normal sectional shape of the thread.

The thread lead is small, the nameplate of the lathe is available, and can be directly pulled by the lathe handle. When there is no nameplate on the lathe, the required hanging wheels must be calculated. Generally, the manual can be checked, and calculation methods can also be used to find and manufacture the required hanging wheels.

When the general thread lead is greater than 300mm, the spindle speed must be reduced to avoid the spindle grinding speed affecting the quality of the thread grinding, but also to make the operation nervous or damage the parts of the feeder box. The methods of deceleration include: changing the diameters of the main and passive pulleys; adding a gearbox outside the lathe.

The splitting method is the same as that of the multi-threaded car.

The use of grinding rubber thread on a lathe is a highly efficient and high-quality machining process. The grinding method has been adopted successively. Single and multiple rubber threads with a lead length of (1.5 to 1280) mm have been produced. Claim.

6 steps deep hole turning method

Turning holes with an aspect ratio of more than 4 on a lathe, due to the poor rigidity of the arbor, vibrates during cutting, affects the cutting efficiency and the quality of the machining surface, and brings difficulties to turning. Especially when the hole diameter is large and the hole is very deep and has a step, machining is more difficult due to the influence of the tool bar and the rigidity of the machine tool. In order to improve the quality and efficiency of workpiece processing, the tooling shown in Figure 3-4 was designed and manufactured to turn deep holes in the step and it worked well.

The chucks and the center frame are used to install the workpieces on the lathe firstly, and the short holes at the two ends of the workpiece are machined with the internal hole cutters, and one set and a special cutter bar are provided for each. When turning the long hole in the middle, first set the left end of the support set in the workpiece hole, and then install the workpiece on the lathe, adjust the length of the cutter head on the cutter bar, and insert it into the workpiece hole together with the left end bearing sleeve. , Use a knife pad to adjust the height of the arbor, and fix the arbor on the square cutter of the lathe, so that the arbor can freely slide in the sleeve, so that the workpiece can be rotated and the cutting can be started until the longitudinal depth of the workpiece. When the work piece is finished, move the large carriage backwards and withdraw the workpiece from the workpiece together with the bearing sleeve and the tool bar on the right end. When processing the second piece, the left end of the bearing sleeve is installed, the workpiece is clamped, and then the knife bar is extended into the left end bearing sleeve of the workpiece, and the right end bearing sleeve is installed to start the turning of the second workpiece.

The length of the cutter head extending out of the knife bar h is calculated as follows:

Tooling features: Both ends support the shank with a bearing sleeve, which greatly increases the rigidity of the arbor, so that the cutting without vibration, to ensure the roughness of the surface has been processed; both ends with the bearing sleeve to support the arbor turning, ensuring the hole Position accuracy; easy to operate, more than 5 times more efficient than traditional hole-expanding methods.

7 How to adjust the center frame when turning large hollow workpieces

When turning the inner hole and end face of a hollow workpiece with a large length and diameter, a center frame is used. If the center frame is not adjusted properly and the axis of the workpiece does not coincide with the spindle centerline of the machine tool, the taper error of the end face center and the bulge and hole will occur during processing. In severe cases, the workpiece escapes from the chuck and causes an accident.

When mounting such a workpiece, one end of the workpiece uses a three-jaw chuck or four-jaw chuck, and the other end is placed on the center frame. Then plug a piece of wood in the hole of the workpiece or stick a piece of paper with the butter on the end face of the work piece, lean the tip of the tailstock against the board or the paper, select the lower spindle speed, and turn the work piece for a week or two. At this time, a circle is drawn on the top of the board or the paper, and then the center rest is adjusted so that the center of the circle is aligned with the tip of the top. This basically makes the centerline of the workpiece and the axis of the spindle of the machine tool. Basic coincidence. After semi-finishing, if the flatness of the end face and the cylindricity of the hole are measured to be out of tolerance, micro adjustments to the three brackets of the center frame are performed and eliminated.

8 skillfully take the center drill tip broken in the center hole

When the center hole is drilled, the center drill is often broken in the center hole because the center of the lathe tailstock is inconsistent with the center of rotation of the workpiece, or the force is too large, the workpiece material is plastically high, and the chips are blocked.

If you use the method of expanding the center hole, then the center hole will change the original size, failing to meet the quality requirements. At this time, as long as a sharpened steel wire is used, insert the tip into the chip flutes of the drill tip in the center hole, move the drill bit a few times, and then move it with a magnet or magnetic table seat to break it in the center hole. The inner center drill tip was removed.

9 Defect elimination method when turning an elongated shaft

(1) Gull-shaped. After turning, the two ends of the workpiece have a small diameter and a large middle diameter. The reason for this defect is that due to the poor rigidity of the slender shaft, the contact between the supporting claw of the tool holder and the workpiece surface is not real, and the wear creates a gap. When turning to the middle part, the turning tool will act due to the radial force. The center of rotation of the workpiece is pressed to the right of the center of rotation of the spindle, so that the depth of cut is reduced, and the rigidity of both ends of the workpiece is good, and the cutting depth is basically unchanged. As the middle produces a "knife," the elongated shaft is bulged.

Elimination method. When following the tool holder claws, be sure to make sure that the claw surfaces are in contact with the surface of the workpiece without clearance. The leading angle of the turning tool should be selected as 75°~90° to reduce the radial force. With the tool holder claws, cast iron with better wear resistance should be selected.

(2) bamboo shape. The shape is bamboo-like, and its pitch is approximately equal to the distance between the holder support claw and the cutting tool tip, and it is a cycle. The reason for this defect is that due to the large clearance between the large pallets and the middle pallets of the lathe, the centrifugal force caused by the bending of the rough material and the reference knife position at the support of the knife holder, the “knife” is produced when the knife is produced. The diameter of the car out of the section is slightly larger than the reference section, continue turning and turning, contact with the knife support claws to contact the workpiece to a large diameter, so that the center of rotation of the workpiece is pressed to the side of the turning tool, turning the workpiece diameter is reduced. In this way, the cutter head is successively supported on different diameters of the workpiece, so that the workpiece leaves and approaches the turning tool, forming a regular bamboo shape. In addition, the tool holder jaws follow the tool, and the force is too great. The center of rotation of the workpiece is pressed against the turning tool, which causes the diameter of the vehicle to become smaller. The tool continues to move. This cycle also forms a bamboo knot.

Elimination method. Adjust the gaps between machine parts and enhance the rigidity of the machine. In the case of the knife holder claw, do not make the claw surface contact with the workpiece, and do not use force. The depth of cut (0.05 to 0.1) mm is used at the cutting station to eliminate the "letting knife" phenomenon when cutting a knife, and the depth of cutting is required to grasp the rules of the machine tool and grasp it flexibly.

10 Reversal knurled

The traditional positive knurling is that the chips can easily enter between the workpiece and the knurling during the rolling process, causing the workpieces to be subjected to excessive forces and causing disordered buckles and ghosting. If you reverse the spindle, you can effectively prevent the above drawbacks and roll out a clear pattern of lines.

11 How to prevent the center drill from breaking when drilling a small center hole

When drilling a center hole with a diameter of less than 1.5 mm on a lathe, the center drill can be easily broken. Except for careful handling and swarf removal during drilling, do not lock the tailstock when drilling, allow the tailstock's own weight and the friction of the machine tool rail to drill. When the resistance to drilling is too great, the tailstock will recede on its own and protect the center drill.

12 sets of small eccentric workpieces

Use the sleeve shown in Fig. 3-17 to clamp the eccentric of the workpiece. The clamping efficiency is 6 to 8 times higher than that of the four-jaw chuck.

Knowing the eccentricity e and the diameter of the outer circle of the workpiece Φ2, the inner diameter Φ1 of the jig sleeve can be obtained, Φ1=2e+Φ2. When the inner diameter of the processing jig set is Φ1, it is necessary to pay attention to the precision of the inner hole so as not to affect the dimensional accuracy of the eccentricity of the workpiece.

13 Spinning Method

Screw conveyors are used in factories that transport granular materials. When the screw shaft in this mechanism is manufactured, its spiral pieces are welded with steel plates. This spiral plate has a high tooth profile, a small base diameter, and the outer diameter and journal must be coaxial, as shown in Figure 3-22. To achieve this requirement, the outer diameter of the screw shaft must be turned with a lathe.

This kind of shaft is generally long. When processing the outer diameter, the pitch is large, the depth of teeth is small, the teeth are thin, and the rigidity is poor. It is interrupted cutting, and the teeth are subject to vibration due to cutting, which makes them unable to cut normally, and it is also damaged. Tool. In order to solve this problem, it is necessary to reduce the cutting speed, reduce the depth of cut and the amount of feed, so that the work efficiency is greatly reduced.

In order to improve work efficiency and quality, a simple and easy method of turning threads is adopted. A hanging wheel is hung by the pitch of the screw shaft, and a large lead screw is used to drive the large tool to turn the tool. When the car is finished with the first knife, remember the scale of the dragging plate. After the big plate is returned, use the small knife holder to move forward (0.5-0.7) mm, and then start the second knife, so that it is good to get the cylindrical wheel.

With this method, the tooth tip of the screw shaft turned out is smooth, basically eliminating the interrupted cutting, and the machining efficiency is improved by nearly 10 times compared with the original.

14 lathe nameplate external thread processing

In many mechanical transmissions, the pitch and lead of multi-head worm, multi-head screw, multi-head helical spline, variable lead worm, double-lead variable-thickness worm, helical gear worm, etc. are not found on the nameplate of the lathe. Processing brings difficulties. A solution to the lack of a desired pitch (or lead) on the nameplate of a lathe is introduced, so that it is possible to dispense with the trouble of being a hanging wheel.

For example, the worm on an imported milling machine that meshes with a helical gear has a normal module of 3.175 and a circular module of 3.184. No 3.184 module can be found on the lathe. To process, the worm has to be calculated and manufactured. After calculation and analysis, the modulus pitch is converted into a metric pitch, that is, 3.184×3.1416=10.003mm, so that it can be processed at a pitch of 1Omm.

In equipment overhaul and maintenance, the pitch of the thread is measured in metrics, so that a non-standard thread pitch occurs. In fact, the thread is divided into ordinary, inch, module, radial and non-standard threads, and their pitch can be converted to each other. Such as 9.4248mm, 12.5640mm, 12.7mm, 25.4mm and 7.9756mm, etc., can be handled by other types of threads, the result is P = 9.4248mm, P = 12.6564mm, respectively, modulus 3 and modulus 4.

Another example is 12.7mm, 25.4mm, 2 threads/inch and 1 tooth/inch inch threads, respectively. P=7.9756mm is a radial pitch thread with DP=10.

15 Boring Tooling with Large Long Cone Hole

When a large-diameter, long-length inner taper hole is machined on a lathe, if a general turning method is used, the knife bar has poor rigidity, vibration during turning, a small amount of cutting, and even cutting. For this purpose, the tooling shown in Fig. 3-34 was used, and many large-scale inner bores or inner cone bores were successfully machined.

During machining, one end of the workpiece is chucked and the other end is supported by a center frame. Put an anti-tip in the spindle hole of the lathe, position one end of the arbor with a steel ball, and use the connecting sleeve and fastening screw at the other end to fix the cutter bar on the sleeve of the tailstock of the lathe so that when the workpiece rotates, the arbor does not Turn it. The cutter head can only slide axially due to the key on the arbor. One end of the wire is fixed on the cutter head, and the other end is fixed on the large drag board of the lathe. When the large carriage moves longitudinally, the cutter head is pulled to move axially to complete the feed movement and carry out cutting.

Before the arbor is installed, the tailstock of the lathe must be placed in front of the large carriage so as to facilitate the movement of the movable cutterhead by pulling the large iron plate. The amount of feed can be obtained by adjusting the handle of the reamer box. When machining the taper hole, the tailstock may be offset so that the axis of the arbor and the workpiece axis are offset by an oblique angle in the horizontal direction. When the cutterhead returns, push the cutterhead with your hand.

This tooling is used to machine large bores on lathes. The operation is very convenient. The structure is also simple and the rigidity of the tool bar is good.

16 Change the number of active gears of the hanging wheel box to increase the range of the worm screw thread

If the number of teeth 32 on the drive wheel of the C620-1 turning box is increased to 48 teeth, the module thread that is not on the nameplate can be machined. If the teeth of the drive wheel 32 are changed to 64 teeth, then the worm gear can not be limited by the spindle speed ratio, and a low-speed finisher can be used to improve the surface roughness of the thread.

17 How to reduce the surface roughness of elongated shafts (rods)

The process for reducing the surface roughness of elongated shafts (shafts) on a lathe is one using a single wheel honing method and the other using a rolling method. This is a simple tool and process used on the lathe to solve the effective measures with low roughness requirements and grinding without grinders.

After finishing the slender shaft (bar) on the lathe, if the roughness does not meet the requirements of the drawing, a single-wheel honing method can be used to rework the workpiece surface, which can reduce the roughness of the workpiece surface from Ra 6.3μm to the bottom. (1.6-0.2) μm. The angle between the axis of the honing wheel and the spindle axis of the lathe is generally 28° to 30°. The angle is large and the efficiency is high, the roughness is large, the included angle is small and the efficiency is low, and the roughness is low. The honing wheel speed is generally (30 ~ 60) m/min, the feed rate is (0.5 ~ 2) mm/r, and the maximum value is selected when rough. The pressure of the honing wheel on the workpiece is (150 to 200)N. For less rigid workpieces, follower turrets should be used. The grain size of the honing wheel is generally 100# to 180#. If the roughness is to reach Ra0.2, the grain size of the honing wheel should be a lubricating fluid for W40~W280 honing, and kerosene or diesel oil with 5%~10% oleic acid added. . In the absence of conditions, ordinary emulsions can also be used for cleaning and lubrication of the honing process.

Rolling of slender shafts (rods) can efficiently reduce surface roughness while increasing surface hardness and wear resistance. Because of the poor rigidity of the workpiece, the head must be used when rolling. The method used is the same as that of the elongated shaft of the roughing vehicle. That is, the head is placed in front of the rolling tool, so as to avoid scratching the surface of the workpiece with the tool holder. Both rigid and elastic rolling tools can be rolled on the elongated shaft (rod). Rolling times are generally no more than two times. The rolling speed is (20 to 30) m/min, and the feed rate is (0.1 to 0.2) mm/r. With oil lubrication, it can also be lubricated with an emulsion.

18 Method for Correcting a Workpiece with Copper Rods

The correction of the workpiece, also known as alignment, is a method of checking whether the mounting of the workpiece is in the correct position before turning the workpiece. The purpose of the calibration is to ensure that the rough balance of the workpiece is basically the same as for the roughing, and to ensure that the relative position of the surface to be machined and the surface to be machined meets the requirements when the semi-finisher and the finisher are finished. Correcting quickly and correctly is an important measure to ensure product quality and shorten the auxiliary time.

The method of correcting workpieces with copper rods is a rapid correction method that is performed when the outer circle and the end surface of the workpiece are roughed and then installed, as shown in Figure 3-41. A copper rod or aluminum rod is clamped on the lathe tool holder, the workpiece is slightly clamped on the three-jaw chuck, and the lathe is started to rotate with a rotation speed of about 100 r/min, so that the copper rod contacts the workpiece end surface or the outer circle and is shaken by hand. The dragging plate exerts a certain pressure so that the surface of the workpiece is completely in contact with the copper rod, and then the copper rod is slowly detached from the workpiece, and then the workpiece is clamped and the workpiece is calibrated.

This correction method is rapid and accurate, and can reach a certain accuracy. If the workpiece is clamped reasonably (less than 10mm), the surface of the workpiece is smooth, and the radial runout of the shaft and the runout of the disk workpiece are not greater than 0.02mm.

19 How to Straighten Slender on a Lathe

The slender rods must be straightened before turning, otherwise the machining allowance will not be uniform and the car will not be round, or the curvature of the rod will be increased due to the bending and centrifugation, and it will not be turned. The following method can be used for the slender rod alignment on a lathe.

(1) Using the hammer method. First, one end of the slender rod is clamped about 10 mm with a three-jaw chuck, and one end of the slender rod is supported. Rotate the work at a slower speed and use Chalk to draw a high point on the part and stop. Hold a piece of concave iron in the left hand so that the concave surface rests on the opposite side of the high point of the workpiece. The right hand takes the hammer to hit the high point of the workpiece. The size of the striking force is proportional to the bending of the workpiece. This repeated several times, the workpiece is straightened. This method is suitable for thin and long rods.

(2) Leverage pressure method. After the elongate bar is installed on the lathe, the car is rotated to rotate the workpiece, and a 300 mm long wooden stick is placed on the middle and square cutters to swing the middle pallet so that the stick is pressed against the curved part of the workpiece. Continue to move the middle plate, tightly with the top of the tailstock to prevent the workpiece from coming out. Wait for the workpiece to continue to rotate for a few seconds, and then slowly withdraw the middle plate, and loosen the top of the tailstock properly, depending on whether the workpiece is straight. If it is still bent, continue the above method until it is straightened. This method is suitable for short workpieces.

(3) Counterattack. In the case that the slender rod is relatively long and the diameter is relatively large, first drill the center hole at both ends and lift it with the spindle tip and the tip of the tailstock of the lathe. Then, turn the workpiece by hand to find the high point on the workpiece and mark it with chalk. At this time, use a piece of iron about 40mm wide and 40mm wide, longer than the lathe's large guide rail, or a relatively large piece of wood, and place it across the large guide rails. Put a head on it instead of the 60° pointed shape instead of a V-shaped or Concave-arc screw jacks are supported on the high point of the workpiece to bend, and some are forced hard. The left hand holds the workpiece by hand, and the right hand hits the bent low point of the workpiece with the round head of the hammer. The number of strikes, the strength, and the length of the work piece are proportional to the size of the bend. Straightened workpieces are not easy to restore bending.

In addition to the method described above for straightening the slender rod on a lathe, it can also be used for visual inspection outside the machine tool and visually calibrated on the platform using the above method.

20 Turning Tools for Inner Spherical Surface in Deep Hole

When turning workpieces such as plastic, nylon and plexiglass shown in workpiece 1 in Figure 3-61, it is required that the inner hole cylindrical surface be connected with the inner spherical surface in the deep hole. The connection point A must be very smooth and have no steps. This gives processing belts. Difficult to come. For this reason, when turning the inner hole and inner spherical surface, it must be completed in a finishing pass.

In order to process the inner hole of the workpiece, the inner turning tool shown in Fig. 3-61 is made first. The material of the blade 2 is a tool steel or an alloy tool steel, and quenching is HRC (60 to 62). Production method: first turning a blank on the lathe, heat treatment quenching, grinding both ends, using the insert hole and the mandrel to install, in the cylindrical grinding or tool grinding outer circle and back angle to the requirements, and then according to the shape of the blade to excess The parts were rubbed away to prevent the turning of the hole and prevent turning. The blade is then screwed onto the arbor so that the rake face of the blade is close to the center of the arbor so that the lower part of the arbor does not get in the way. This can also increase the cross-sectional area of ​​the arbor and increase the rigidity of the arbor.

When turning the inner hole, drill with a drill first, and use the inner hole cutter to rough the inner hole of the car. When finishing the car, attach the tool shown in Figure 3-61 to the lathe side of the lathe so that the blade and the center of rotation of the workpiece are at the same height. First use this knife semi-finish car hole, the hole depth basically meets the requirements. After the cylindrical part of the inner hole of the finishing car, the inner spherical surface of the deep hole is also turned into a car at the same time. At this time, the inner hole is completely finished. This kind of tool and operation method make the inner hole and the inner spherical surface without tool marks and is very smooth.

21 turning plane thread

The so-called flat thread is the thread processed on the cylindrical or disk end face. The trajectory of the turning tool with respect to the workpiece is an Archimedes spiral, which is different from the normally processed cylindrical thread.

Turning the plane thread on an ordinary lathe generally adopts a light beam drive, so that the middle dragging plate screw rotates, driving the lathe in the lathe to move horizontally and moving the knife for turning. This requires that each revolution of the workpiece, the middle plate moves the workpiece on a pitch.

When the workpiece pitch is not strictly required, the pitch of the available flat thread can be divided by the multiple of the lathe (such as C620-1 lathe can be increased by 2, 8 and 32 times). Use the quotient to select the nameplate of the lathe. The amount of horizontal feed, and pull the handle box handle as required, then increase the pitch handle on the spindle box to increase the pitch position, and the spindle box on the shift handle to the required position, install the tool , can carry out plane thread turning.

When the workpiece pitch is strict, it must be replaced with a hanging wheel. Before calculating the hanging wheel, according to the above method, choose an approximate amount of horizontal knife, and pull the forward tool box, increase the pitch and shift handle, and carry out transverse cutting. Then use the whole number of the spindle (5 revolutions or more) to remove the distance moved by the carriage. The resulting quotient is the actual pitch of the lathe. Under normal circumstances, it will not be equal to the required pitch of the workpiece. Therefore, it is necessary to calculate the replacement of the hanging wheel. Its formula is

In the formula i - gear ratio or transmission speed ratio;

P work - workpiece pitch (mm);

P real - measured pitch (mm);

Z1, Z3 - is the number of teeth of the driving gear;

Z2, Z4 - is the number of passive teeth.

Example: The plane thread pitch of the workpiece is P = 8 mm, and the measured pitch P = 8.24 mm. Find the number of teeth on the lathe.

Solution 1 Use the calculation method:

Answer: The number of active gear teeth is 100 and the number of passive gear teeth is 103. The hanging wheel is a single-type hanging wheel, and any gear with a middle number can be used as the intermediate wheel.

Solution 2 Use the table lookup method:

Check the "Metal Cutting Handbook" published by Shanghai Science and Technology Publishing House or the "Machinery Worker Cutting Handbook" published by the Machinery Industry Press to get the corresponding number of hanging gear teeth.

Answer: Z1=100, Z2=80, Z3=70, Z4=90.

When turning, it is best to use an elastic arbor, and the geometric parameters of the cutter head are the same as those of the cylinder, but the double relief angle must be worn in the auxiliary relief angle on the inner side of the cutter head to prevent this part from turning. The lathe spindle is used to move the tool forward and backward and the tool is returned. There are two ways to eat a knife: one is to use a lathe tool holder to eat a knife and a retract knife, and a small halves of the hoop is counted; the second is to install a magnetic watch stand and a dial indicator on the large guide rail in front of the large carriage to control the size. The position of the pallet and the amount of knife to be eaten, and use a large pallet to eat knife and retreat.

In the process of turning the plane thread, in addition to the square thread, the threads of the other teeth need to be turned on like a turning cylinder thread to finish both sides of the thread. There are two ways to “catch up” the knife: First, use a large plate to eat the knife and retract the knife, rotate the small knife holder counterclockwise by 90° and fix it, and shake the handle of the knife holder when you “rush the knife”: Second, use When the knife or knife is to be eaten and retracted, when the knife is to be “rushed”, the cutter head is placed outside the workpiece, the spindle is stopped in the cutter, but it must be without reverse rotation, then the worm handle will fall off. , Rotate the handle of the dragging plate to the value of “catch up knife”, and then lift off the worm handle. To use this method to “catch up”, the clearance of the drive chain must be eliminated, which direction it needs to “shoot”, and the middle carriage must go in the same direction. After "cutting the knife", the cutter head is gradually cut into the workpiece.

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