Thread rolling with manual thread rolling dies. Thread rolling and tool types

At present, thread rolling processes are widely used in industry. The shaping process during rolling occurs without chip removal. It consists in TGM, that the working part of the rolling tool is pressed into the material of the workpiece and, as a result of its plastic deformation, forms a thread. By rolling, you can get a thread of the 2nd class of accuracy and a surface roughness of the 8th-9th class. The rolling process is characterized by high productivity, increased strength and thread wear resistance and is economical in mass production.

The most widely used in the mass processing of threads on parts made of structural styles and non-ferrous metals was knurling with two flat dies (Fig. 176, a).

The kit usually consists of three rollers mounted at an angle of 120°. This ensures good centering of the workpiece. The rollers have an annular thread and rotate freely in the die body. The profile of the turns of the rollers is shifted relative to one another by 1/3 of the step, which is necessary for the formation of a screw thread on the workpiece. The rollers have intake and calibrating parts, which provide a rational flow of the deformed metal during thread rolling with axial feed.

The dies do not open at the end of the working stroke and after the end of thread rolling they are screwed together. Greater productivity is provided by thread rolling heads, which favorably differ from thread rolling dies in that their rollers automatically diverge at the end of the working stroke and the head is removed from contact with the workpiece without screwing. Rolling heads can be operated with or without rotation, depending on the equipment used. Heads and dies make it possible to roll threads of the 2nd accuracy class using the self-tightening method. To obtain more accurate threads, it is necessary to apply forced feed from the lead screw.

The rolling method can also process internal threads. For rolling internal threads larger size, a knurling roller is used, which is inserted into the hole in the workpiece (Fig. 178).

During the rolling process, the roller and the workpiece rotate around their axes. At the same time, the roller is given a radial feed, as a result of which the roller rolls along the hole and its threads, pressing into the material of the workpiece, form the thread of the part. When rolling deep threads, the tool is given an axial feed, which leads to a decrease in rolling forces.

Thread rolling large sizes it is also produced with rolling holders and heads (Fig. 179).

Rice. 179.

Rolling is one of the most progressive methods thread formation on various parts and, first of all, on screws, studs and taps. At present, the thread rolling process is particularly widely used in mass and large-scale production. For example, in the production of taps, it has almost supplanted all other methods of obtaining a thread.

Rolling process

When rolling as a result of the action of large radial forces, the threads of the tool deform the metal of the workpiece and form a thread on it. Processed surface layer metal gets higher mechanical properties(increase in hardness and strength). This is due to the fact that when rolling, the fibers are not cut, as is the case when threading with any cutting tool, but are deformed according to the thread configuration. Rolled taps can have increased tool life due to the sealing of the surface layer. However, if the wrong material is selected or technological process surface flaking and flaking of material along the threads may occur.

In practice, two types of rolling tools have become widespread: dies (Fig. 366, a) and rollers (Fig. 366, b). Both tools work as a set consisting of two pieces.

roller rolling

Roller rolling is a more advanced process than die rolling. Rollers, in comparison with dies, work with low pressures that arise during the rolling process. This makes it possible to obtain threads on hollow or thin-walled parts, as well as on parts with increased hardness (up to HRC 35-40).

The thread on the roller can be obtained by profile grinding, which provides a higher accuracy of the rolled thread (2nd and 1st grades) and a high surface finish (7-9th grades). Rollers provide ease of installation and adjustment to the size of the rolled thread. Dies cannot give such accuracy due to design flaws and the complexity of machine maintenance.

When rolling with rollers, the formation of threads depends on the radial feed and peripheral speed of their rotation, which can be varied within certain limits. By appropriately selecting the mode, it is possible to obtain threads even on parts made from low-ductility materials, such as high-speed steel. For dies, this is either impossible, or is associated with low durability, since the thread formation in them ends at the intake part, the length of which is relatively small. Significant advantages of the first method are also the small dimensions of the machines, the simplicity of their adjustment and maintenance.

Rollers on conventional machines allow threading on parts from 2 to 60 mm, while dies from 3 to 24 mm.

Disadvantages of rolling

The disadvantage of rolling with rollers is its reduced productivity (60-80 pieces per minute) compared to rolling with dies (100-120 pieces per minute).

Roll rolling is used in the manufacture of parts with fine threads (for example, taps), while rolling with dies is used for screws, studs and other similar details with low precision thread.

Thread rolling is a process of plastic deformation of the workpiece material. The knurling tool is pressed into the workpiece. The material of the workpiece, being deformed, fills the cavity of the tool, forming a protrusion of the processed thread.

3.7.1 For rolling external thread three methods are used: a) with a flat tool with tangential feed - rolling with flat dies; b) driven round tool - rolling with rollers with radial feed; c) non-driven round tool with tangential feed - rolling with rollers with axial feed.

a) Thread rolling with flat dies

Rice. 21.1

The thread on the dies is made with the same profile as the thread being machined, the angle of the thread on the dies is made opposite to the thread direction of the workpiece. The length of the dies is selected depending on the average thread diameter in accordance with GOST 2248-60. The dies are installed parallel to each other with a shift of 0.5 steps in the middle of the dies.

b) Thread rolling with cylindrical rollers with radial tool feed

Rice. 22.1

The rollers rotate synchronously; for this, the machine has an appropriate kinematic connection. One of the rollers receives a radial movement. On the rollers, a multi-start thread is made in the opposite direction, but with the same angle of inclination with the workpiece, therefore

here d2 and D2 are the average diameters of the thread of the workpiece and the knurling roller, respectively, and N and n are the number of threads of the roller and the workpiece.

here T is the length of the thread at the roller

t is the length of the thread of the workpiece.

Apply rollers with open and closed contour. For rollers with an open contour, the thread root does not participate in the formation of the top of the rolled thread, and therefore is not limited to exact dimensions. For rollers with closed loop the root of the thread forms the crest of the thread being rolled, and therefore the shape and dimensions are manufactured to the appropriate tolerances. Closed loop rollers are used to make threads with an interference fit. The dimensions of rollers for rolling metric threads are regulated by GOST 9539-72.

c) Thread rolling with axial feed.

The most widely used method with rollers with circular threads. The advantage of this method is that the choice of rollers depends only on the pitch of the thread to be rolled. During operation, the rollers are set at an angle to the axis of the part so as to match the direction of the turns of the threads being cut in the annular cutting of the rollers (see Fig.).

Rice. 23.1

The rollers on the side of the part entry into the knurling space have a conical intake section with an angle of 3h50. with this method of knurling, the rollers rotate freely under the action of the rotation of the workpiece, while the workpiece has an axial movement by the amount of the thread stroke in reverse.

3.7.2 Rolling internal threads

There are basically two methods for obtaining internal thread plastic deformation with the help of knurled taps, and with the help of self-tapping screws. The design of the tap-knurler is shown in fig.

In cross section, the working part of the forming machine has the shape of a polyhedron with rounded edges. The intake part is taper thread with a full profile, angle 5h100, number of edges for threads up to M6-3, up to M20-6. The diameter of the workpiece for thread rolling is determined based on the balance of the metal before rolling and after it

here d- outside diameter rolling;

P - thread pitch;

dav is the average thread diameter of the forming machine;

d1 is the inner diameter of the thread.

In addition to threading round dies and sliding screws, thread rolling dies are used for thread rolling. This exercise covers thread rolling thread rolling dies type NP1 with a range of thread diameters 4-6 mm.

The following sets of rollers for thread rolling with pitch (mm) can be installed in the NP1 thread rolling die: M4 - 0.7; M5 - 0.8; M6 - 1.

Before thread rolling, a number of preparatory work must be performed.

1. Prepare the workpiece (bolts, screws, studs) for thread rolling:

a) check the diameter of the workpiece, which must correspond to the size indicated in table. 6.

Table 6 Diameter of blanks for thread rolling, mm

Note. All dimensions are given in millimeters.

b) the lead-in chamfer is removed with a file at the end of the workpiece at an angle of 10° to the axis, so that the diameter at the front end of the lead-in is equal to the inner diameter of the thread minus ~0.3 mm;

c) the workpiece is installed and clamped in a vice in a vertical position.

2. Disassembled thread rolling dies are prepared for work:

a) depending on the diameter and pitch of the thread, thread rolling rollers are selected for the die;

Rice. 195. Thread rolling rollers:
a - installation and fastening of the rollers in the die body; b - the location of the rollers in the body of the die; c - the position of the gear rims of the axles and the teeth of the wheel in the body of the die

b) the axles of the rollers 1 (Fig. 195) are installed with the front end with a shoulder on the plane of the workbench;

c) the eccentric neck of the axis of the rollers 2 is lubricated with grease and thread-rolling rollers 3 are put on it;

d) the rollers (assembly) are inserted with their axes into the holes of the body 4 in the order of ascending numbers indicated on the rollers and on the body with marks 1-3 (Fig. 195, b), and on the opposite side of the body (Fig. 195, c) gear rims axes 5 must be paired with the teeth of the gear wheel 6;

e) inserted into the groove of the body gear 6 (see Fig. 195, c) so that the gear rims of the axles 5 are mated with the teeth of the gear wheel, and the protrusion B is located between the two adjusting locking screws 9;

f) the axles of the rollers are fixed (preliminarily) in the body with nuts 5 with washers 7 (Fig. 195, a);

g) the rollers are set to the required thread size; for this, a threaded gauge or bolt is installed along the axis of the die between three rollers;

h) the rollers are brought together so that the crests of their thread tightly cover the thread of the gauge (bolt). Approximation is carried out by two adjusting locking screws 9, one of them is unscrewed, and the other is screwed in the housing 4. At the same time, the screw 9 being screwed, moving the protrusion B, simultaneously rotates the gear wheel 6 and the eccentric neck of the roller axes 2, which bring the thread rolling rollers together (Fig. 195 , a, c).

After the rollers are set to the size, the central gear 6 is locked with screws 9 and the axles of the rollers 1 are finally clamped with nuts 8;

i) the gauge (bolt) is unscrewed from the rollers and free rotation on the axle journals is checked.

3. The thread rolling technique is as follows:

a) a die is applied to the cut end of the workpiece, while the lead-in chamfer must enter without distortion between the three thread-rolling rollers of the die;

b) right hand cover the plate, pressing it down, and turn the plate clockwise with the left hand, using the self-tightening method (Fig. 196, a). Forced feeding of the die to the workpiece is carried out only at the beginning of work - before being captured by the rollers;

Rice. 196. Working methods:
a - thread rolling die for self-tightening; b - thread rolling dies

c) after self-tightening, the die is rotated with the help of handles (Fig. 196, b) rolling the thread in one pass to a given length;

d) by reverse rotation of the die, roll it off the thread, wipe it with a clean cloth and check the quality of the knurling with a ring gauge.

After completing the task, wash off lubricant, wipe the tool with a clean cloth and put it in place.

Specifications. Roller plates.

JBO roller dies are designed for deformable materials with a minimum deformation of 8% and a strength of approx. 900 N/mm2.

Workpiece preparation

The workpiece to be machined must be oriented to the diameter pre-treatment. This diameter, due to the difference in the rolled material, is a reference value and will, if necessary, be gradually increased until the thread profile is completely finished. Subsequent increase in diameter may damage the tool due to overload. Pay due attention to the outside diameter tolerances of the threads.

The chamfer of the workpiece should be after processing 15-20 °, for better rolling. Chamfer and pre-machining diameter must rotate without runout.

The groove at the end of the thread can be made with an angle a up to 30°. With a rectangular groove, the threaded rollers would be chipped and therefore the rectangular groove would have to be placed after the threaded rollers.

Processing speed

We recommend a processing speed of 20 to 50 m/min. Non-ferrous metals are machined in the upper cutting speed range, free-cutting steels in the middle and difficult to machine in the lower range. Necessary condition is enough oil to lubricate and cool the cutting tool.

Roller dies JBO are equipped with rolled profile rollers.

With rollers with a rolled profile, a more precise thread profile and a higher pitch accuracy are achieved. In addition, the rolled profile has a positive effect on the service life of the rollers (in the case of material that is difficult to machine).

Installation guide for RSV movable threaded rollers with RSV roller holder 2 to 10.

1. Put the rollers on the holder (stand), unscrew the nut until the roller is centered and fits freely. Tighten with locknut.
2. Set the outer diameter of the workpiece to the pre-machining diameter (reference value), turn the thread, check the thread diameter.
3. When adjusting dimensions, first set the thread diameter with a nut. Then set the outer diameter of the thread by changing the pre-treatment diameter, while following the method indicated in the “Workpiece Preparation” paragraph (see above).