Set Screws

A set screw is a cylindrical threaded part. One end is made with a slotted or hex socket drive. The end configuration varies and is selected individually for each case.

Application

Screws are used in machine building, instrument engineering and other industries. The parts are often used to secure components on a shaft — bushings, pulleys, etc.

Set screws prevent radial and axial displacement of the part. The driving tool is selected individually for each case based on the slot/socket configuration.

Types of set screws

The installation method depends on the fastener type. Before installation, a hole must be drilled and tapped with an internal thread. All parts are divided into two groups:

1. Pressure-type. Have flat or round ends. When tightened, they secure the part by pressing against its surface. For example, if a flat-point set screw is installed in a pulley on a shaft, it holds the rotating part against axial displacement. A key is additionally installed with fasteners of this group — it transmits torque from the pulley to the shaft.
2. Penetrating-type. During installation, the screw is turned through the thread of one part and seats into a recess in the other. This eliminates both axial and radial displacement. A key is not required. This type of screw reliably holds a pulley or bushing while transmitting torque.

A properly selected set screw ensures a reliable connection between parts.

Standards compliance

The production of fasteners is regulated by GOST. Fasteners of foreign manufacture are produced to the DIN standard. Set screws are manufactured in accordance with:

1. GOST 11074. A cylindrical part with a full-length thread. Material — carbon and stainless steel, brass and other non-ferrous alloys. The part has no protrusions on the end. The driving tool is a hex key, which allows the threaded element to be fully screwed into the part. Specifications correspond to DIN 913.
2. GOST 8878. A part with a hex socket and full thread. This type has pointed ends — this configuration allows the screw to dig into the part and ensures a reliable fastening. Material — carbon steel, stainless steel, brass, etc., selected based on the installation location. Corresponds to DIN 914.
3. GOST 11075. The fastener is made as a cylinder with external thread and a hex socket. The end has a dog point — a small unthreaded cylindrical pin. During installation, the dog point seats into a recess in the part, ensuring a reliable connection. Parts are produced with M3, M4, M5–M24 thread. Correspond to DIN 915.
4. GOST 28964-91. Externally similar to parts from the previous categories. Has a cup point end. Corresponds to DIN 916. Material — brass, carbon or stainless steel.

Set screws with a slotted drive can have a conical or cylindrical working end. A threaded connection with a slotted drive is not designed for high torque; a hex key is used for a more reliable connection.

The application of the screws depends on their configuration:

• Flat point (DIN 913). Used in machine building, furniture manufacturing and other fields. Installation requires drilling and tapping a thread in one of the parts. The fastener presses against the surface of the other part with its flat end. Displacement is prevented by friction.
• Cone point (DIN 914). Used in the manufacture of machine tools and machinery. Prevent axial displacement of a pulley on a shaft. Seating the cone point requires pre-drilling the part.
• Hex socket with dog point (DIN 915). Used in machine building and furniture manufacturing. The cylindrical dog point fits into a pre-made hole, preventing displacement of the parts relative to each other. This type of fastener can be used to adjust clearance in assemblies.
• Hex socket with cup point (DIN 916). Used in the automotive industry and instrument engineering. The shape of the working end allows the fastener to be used for joining and adjusting clearances in assemblies. Installation requires tapping a thread in one of the parts.

Advantages and disadvantages of DIN 913, DIN 914, DIN 915, DIN 916 screws

These parts are widely used for joining metal, wood, plastic and other components. This type of fastener has a number of advantages:

1. Reliable connection of parts. The possibility of axial and radial displacement is eliminated — the working end of the fastener presses against the surface or fits into a dedicated recess.
2. No head. The configuration of set screws allows them to be installed in a concealed manner, without drilling additional holes to recess a head.
3. Hex socket. A recess of this configuration allows higher torque to be applied when tightening the fastener without damaging the edges. The hex socket is convenient during installation — the fastener holds well on a magnetic bit.
4. Variety of end point shapes. The configuration of the part is selected individually for each case, taking into account the material of the parts and the shape of the hole.

The disadvantages of fasteners in this group include the need to pre-tap an internal thread in the hole. Unlike self-tapping screws, set screws are installed into a pre-prepared thread, which requires additional equipment.

Before installation, it should be noted that dirt can get into the hex socket, hindering proper engagement of the key. Special plastic caps can be used to avoid contamination. By correctly selecting the fastener and following the installation procedure, a reliable connection can be achieved.