How is threading taps and dies

When performing a variety of works, almost all are faced with the need for a threaded connection. Threading dies and taps at home allows you to solve the problem of fixing the necessary parts.

The scheme of cutting external and internal thread.

These tools themselves are widespread and are available in almost every home. Having the right set of different tools allows threading taps and dies on almost any connecting elements.

What is a tap?

In the general case, the tap is a rod with cutting edges formed by straight or helical slots. Its main purpose is the creation of internal threading. The tap includes working and tail parts. The working part, respectively, contains the cutting and calibrating zone. The working part is made, usually in the form of longitudinal chip grooves (sometimes in the form of helical grooves). The cutting zone has a conical shape, the calibrating zone is cylindrical. The shank is made in the form of a cylinder with a square at the end.

Tap drawing.

On the cutting surface of the working part there are teeth of a certain shape that defines the parameters of the thread. The following tooth sharpening parameters are distinguished: a back angle (6-10º), a rake angle (for steel - 5-15º, for bronze - 0-5º, for light alloys - 25-30º). Taps are made with different precision processing of their surface, which determines the accuracy class when cutting threads.

Taps are divided into shape - cylindrical and conical; to destination - manual, machine and nut; by completeness - single and complex (a set of 3-4 pieces for the sequential production of thread with increased pitch). The main material for taps is steel U10A and U23A.

The choice of the tap is made according to the following parameters: pitch and depth, diameter of the hole for cutting, type of hole (blind, through), accuracy class. In addition, according to the material being processed, the taps are divided into the following types: for light alloys, for stainless steels, for carbon steel and cast iron.

What is a die?

In the general case, a die (lerka) is a cutting tool for the manufacture of an external thread. It is made in the form of a very strong nut, in the hole of which the cutting edges with teeth are made. The teeth are arranged so that they form a coil. The cutting part of the die is formed as an internal cone. The thickness of the die is usually 8-10 teeth (turns).

Drawing of a round die.

Dies are divided by type - into solid, split and sliding; in shape - round, square, hexagonal, prismatic. For manual slicing, one-piece round is most often used. Up to five recesses (grooves) are made for fastening in the holder (driver) on the surface of a round die.

The die hole forms a working part consisting of three zones. Top and bottom of the working area are made conical sections - cutting zones. In the central part of the cylindrical area forms a calibrating zone. The angle of taper of the cutting zones is 50-60º. The shape of the cutting tooth is set by the front sharpening angle in the range of 15-20º (for carbon steels) and the rear angle in the range of 6-8º.

The round die is designed for cutting metric, inch and pipe threads. Dies provide cutting with accuracy not lower than the second class. One of the main features of the use of dies is that all three zones of the work area are involved in the formation process.

Thread features

In the general case, cutting a thread means cutting a helical groove along a surface having a cylindrical or conical shape. According to the location of the surface thread is subdivided into external (screw, bolt) and internal (nut). According to its purpose, the thread can be mounting or running. The shape of the profile can be applied triangular, rectangular and trapezoidal. The direction can be left or right.

The fastening thread is mainly triangular and is made on the fastening details. Chassis with a complex profile and manual method is rarely cut.

Classification of thread types.

The main parameters include:

• outside diameter;
• step;
• lifting angle;
• profile angle.

In their mind the most interesting are metric, inch and pipe thread. Metric has a triangular profile, as the mounting thread of a cylindrical type with small and large pitch. Metric is used most often. Its main parameter is the angle of the thread profile, which should be equal to 60º. Pipe has a cylindrical shape and is used to connect tubular parts.

Devices and devices

Threading is done by rotating and translating the corresponding tool. To do the work with dies and taps, it is necessary to fix them, direct them in the right direction, as well as ensure their simultaneous rotation and slow forward movement. For these purposes, special devices or devices are used.

Cutting external thread dies is made using a die holder (driver). Such a device is a sleeve with handles in both directions. 4-6 threaded holes are drilled in the sleeve, in which screws (bolts) are screwed in to fix the plate inside the sleeve holder. For threading, the die is inserted into the sleeve and firmly fixed with screws. When attaching, the plate is centered with respect to the holder axis. Handles allow you to create a torque moment manually.

When cutting internal threads using taps, rolls are used. Such a device has a square socket in the center, into which the end part of the tap shank is inserted, as well as two handles for manually rotating it. The locking screws allow you to securely fix the tap in the device.

DIY threading

Scheme of threading dies.

At the first stage, the part is prepared for external threading. First of all, the workpiece is securely fixed in a vice strictly vertically, and the plate must be installed and centered in the die holder. Then it is recommended that the workpiece in the area where the thread will be cut, slightly grind (with a file or emery cloth) to a depth of 0.1-0.2 mm (for soft metals - up to 0.4 mm). To facilitate the entry and centering of the plate at the end of the workpiece, it is necessary to chamfer at an angle of up to 40º.

Then, the introduction of the plate and cutting of the first turns is necessary, which is the most important one, which determines the quality of the whole process. When installing on the workpiece, it is necessary to strictly center the instrument and ensure its horizontal position relative to the table. At the moment of plunging into the metal, the die must be forced into the workpiece, while making a smooth turn with the handles of the die holder. The axis of the plate and the axis of the workpiece must be strictly aligned. The value of the translational feed must be equal to the pitch of the thread. The bias in the formation of the first turns is absolutely unacceptable.

After the plate enters the workpiece at about half its thickness, the pressure on it can be stopped. At the third stage, the plate is self-tightening, and it will continue threading under the action of the torque.

Tapping

Tapping is in many ways similar to tapping with a die, but when working with a tap you should not rely on self-tightening of the tool. The whole process should occur with a forced feed of the tap in the longitudinal direction. Work should begin with fixing the tap in the crank. Then, a chamfer is made at the top of the hole in which the thread is cut.

The tap is strictly vertically inserted into the hole, and by turning the knob while simultaneously pressing down, the first turns of the thread are formed.

Gently rotating the knob and evenly giving the tap forward, the thread is cut to the desired length.

When cutting tap it is necessary to ensure the constant removal of metal chips, so as not to damage the teeth. High-quality tapping requires the fulfillment of four important conditions: the use of a sharp and high-quality tap; during the cutting process, it is necessary to cool the tool with kerosene or oil; strict compliance of the selected tap with the required diameter; permanent chip removal.

When cutting with taps and dies, you must have the following tool:

• vice;
• knob;
• holder;
• a set of taps;
• set of dies;
• pliers;
• grinding wheel;
• file;
• hammer;
• calipers;
• micrometer;
• screwdriver;
• wrenches.

Tapping and dies is quite a simple thing. You only need a neat attitude and a certain skill.