The optimal diameter of the drill under the thread

No plug-in connection can exist without a threaded joint of parts. It must be said that any hardware with external threads, for example bolts, can be purchased at any specialized shop. From the inside is much more complicated. It is cut manually or on special machines.

Thread classification

Thread classification

To get it, you must first drill a hole in the workpiece that must match the diameter of the tool to be cut. Each such hole requires a specific tool size. It is for this purpose that the diameter of the drill for the thread is selected.

The industry produces drill diameters of a completely different size. It can begin with a minimum of 0.5 mm and end with large conical drills, the dimensions of which are usually 0.05 mm. Therefore, by drilling you can get a variety of holes needed to perform the process.

The main characterizing parameters

When it is required to make holes having a large diameter, special machines are used in which the drills are made with a tapered tail. All ordinary drills have a cylindrical tail. The cone of a big drill corresponds to the fifth size. The size of the cone is in direct proportion to the size of the drill. The large diameter of the drill requires a large cone. Here are indicative data:

Diameter: 6-10 mm, cone: 11-22 2 mm.

Table of the selection of the diameter of the drill for ruzbu

Table selection of the diameter of the drill for ruzbbu.

The largest drills must have a fifth cone. When it is necessary to make an internal thread, the diameter of the hole is chosen according to the diameter of the thread and the size of the threaded pitch. In engineering drawings, such data is shown as M8 × 1. In this case, the letter "M" shows the metric thread, the figure indicates the thread pitch. When they simply write “M8”, without numbers, the use of a standard large step is implied. Such a threaded step is most preferable, as it is standardized for most sizes.

Each diameter requires a specific hole size. For the definition, a special table is used, in which the most popular sizes are indicated. Any mechanic or a housekeeper is facing them.

Back to table of contents

Threading recommendations

By its appearance, the thread resembles a helical groove having a constant cross section. The thread has two types:

  • outdoor;
  • internal.

Threaded connections are used almost everywhere. With their help, you can give the rotation of the details of the translational motion. Any mechanism, any complex machine can not do without threaded joints.

It is divided into several groups:

  • single entry;
  • multiple.

The direction of movement of the guides affects the separation of the thread into two types:

  • left;
  • right.


There is also a division of the thread into several types according to the available size system:

  • pipe;
  • metric;
  • inch.

It characterizes the metric thread peculiar profile, having the form of a triangle. Its angle reaches 60 °. All dimensions measurements are in millimeters. With a large step, it is marked with numbers with the addition of a letter. Usually the numbers show the size of the outer diameter. Each technical drawing necessarily shows the characteristic thread type "M6" or its equivalent. When they want to show a metric thread with a non-standard small pitch, they specifically add a number indicating the pitch. Marking is as follows: M6 × 0.6.

Another profile angle is distinguished by a special inch thread. It usually reaches 55 °. The size of the hole is shown in inches; the number of threads measures the pitch.

The main difference between pipe threads is its original diameter, which is based on the size of the pipe hole. In this case, the cutting is done only outside.

To perform the cutting operation, use a variety of equipment, such as:

  • drilling machine;
  • turning park;
  • thread-cutting devices.

In addition to mechanized methods, cutting is often done manually. To get an internal thread, locksmiths use special threaded taps. Cutting outside done with dies.

The table of the choice of taps for cutting thread

The table of the choice of taps for cutting threads.

Taps are also divided into several groups:

  • metric;
  • inch;
  • pipe.

In most cases, hand taps are available in a set that includes three items. The first two are for preliminary operation, the latter is considered to be fine-tuning. It creates the final threaded shape and dimensions. Absolutely every tap has its own number, which is marked on the tool's tail. Sometimes there are only two taps. Then one is considered preliminary, and the other - clean. The material used for taps is high-alloy steel.

Using a die, get an external thread. By design, this tool is divided into:

  • round;
  • prismatic.

For absolutely round dies, a special knob is used, called a die holder.

Back to table of contents

How can I get an internal thread?

You must first select the desired size of the drill to make a hole in the place where cutting is required.

To use the tap, the hole is treated with a countersink until a certain purity is obtained. When cutting is done, a slight extrusion of the material occurs.

Therefore, the size of the drill should be chosen slightly larger than its internal threaded diameter.

Very hard metal does not allow much change in the size of the hole when the thread is cut.

However, when the material has a low hardness, the size of the hole varies greatly. If the size of the hole coincides with the internal threaded diameter, then material will be squeezed out during cutting. Its excess will begin to affect the teeth of the tap. They will start to heat up, shavings will start to stick. Such a thread will have torn threads, the break of the tap is not excluded.

To determine the diameter of the drill, it is necessary to turn to the help of special tables, in which all necessary parameters are indicated. Good luck!

Add a comment