What Is a Button Head Socket Cap Screw?
Button Head Socket Cap Screws are bolts with a rounded hemispherical bolt head that resembles a button when viewed from the side.
The end face of the bolt head is cut horizontally and a hexagonal hole is drilled. To tighten, a hexagonal wrench is used to insert the bolt into the hexagonal hole on the top surface of the head.
As general terms, button bolts and button caps are also synonymous. The shape of button head socket cap screws is the same as that of button cap screws if the nominal diameter of the screw is the same, but button head socket cap screws have a larger nominal diameter than button cap screws.
The standards for button head socket cap screws is the ANSI/ASME B 18.3 Hexagon Socket Button Head Cap Screws.
Uses of Hexagon Head Socket Cap Screws
Figure 1. Example of button head socket cap screws use
Hexagon Head Socket Cap Screws are primarily used to mount and secure components on small machines and equipment where space is limited for installation.
On the mating side where the button head socket cap screws is to be installed, a counterbored hole is drilled slightly larger than the outside diameter of the bolt head and slightly deeper than the height of the head.
This allows the bolt head to be installed without protruding completely. Interference between the bolt head and other parts is avoided, resulting in a clean and neat appearance. In some cases, counterbored holes are not installed and used in the same way as hexagonal bolts.
Compared to hexagonal bolts, the bolt head is smooth and does not catch, so it is safer and less likely to be scratched even if touched by a person. Counterbored holes are drilled in the mounting area to hide the bolt head.
Principle of Button Head Socket Cap Screw
Figure 2. Hexagon socket button bolt
Button Head Socket Cap Screws are fastened with a screw (in this case, “screw” refers only to the screw shape), the same as an ordinary hexagonal bolt. Button Head Socket Cap Screws are often used for fastening by screwing directly onto a tapped female thread without using a nut.
Instead of inserting a wrench into the bolt head like a hexagonal bolt, a hexagonal wrench with a hexagonal cross section is inserted into the hexagonal hole and tightened. Therefore, it is necessary to secure a space between bolt heads and other parts.
However, since the tightening tool for the button head socket cap screw is a hexagonal wrench, no space is needed outside the bolt head, and the button head socket cap screw can be placed in close proximity to it. As a result, designs can be made with smaller dimensions and compact parts and devices can be realized.
The length of the button head socket cap screw is indicated by the length of the shaft part including the threaded part, excluding the height of the bolt head, in the same way as the length of ordinary bolts such as hexagonal bolts.
Other Information on Button Head Socket Cap Screws
1. Proper Use of Button Head Socket Cap Screws
The basic proper use of hexagon socket button head cap screws is as follows:
- Tightening force must be within the allowable range so that the threaded hole between the button head socket cap screw and the object to be fastened will not be broken.
- The repetitive force (due to vibration, etc.) applied to the threaded hole between the button head socket cap screw and the object to be fastened must be within the allowable range.
3. Looseness Prevention of Button Head Socket Cap Screw
To prevent loosening of button head socket cap screws, use an adhesive to prevent loosening, or use bolts that have been treated to prevent loosening.
4. Tightening Tools for Hexagon Head Socket Cap Screws
Figure 3. Types and shapes of button bolt tightening tools with hex holes
To tighten the button head socket cap screw, use a hexagonal wrench or other tightening tool appropriate for the size of the bolt. Compared to wrenches and monkey wrenches, hexagonal wrenches have the advantage of being able to apply a strong tightening force with less force and requiring less work space around the bolt when tightening.
Hexagonal wrenches are available in millimeter and inch sizes, and care must be taken when selecting a hexagonal wrench. Types of tightening tools include L-shaped hexagonal wrenches (hexagonal bar wrenches), T-shaped handle hexagonal wrenches, screwdriver-shaped hexagonal wrenches, and hexagonal bits.
The hexagonal wrenches and hexagonal bits have either a flat or ball point tip shape on the insertion side of the button head socket cap screw.
The shape of the ball point tip is R-processed at the corner so that the hexagonal wrench can be tightened even when the hexagonal wrench is at an angle.