The difference between countersunk bolt and flat head bolt

In this article, the difference between countersunk bolt and flat head bolt will be talked about. Let's explore together!

1. Different concepts

• Flat head bolts: screw body axial surface for the axial extension of the screw thread, its tail end at least one groove. A chip slot in the center of the screw to cut a chip slot, so that the chip slot deep into the screw body and over the center line of a predetermined angle, the main role is to prevent the groove mouth is blocked by chips. In large construction sites and other engineering sites will choose to use more flat head bolts.
• Countersunk bolts: Countersunk bolt is a kind of construction parts. The head is a 90-degree cone, similar to the common wood screw, the head has a tool tightening slot, a font, a cross, an inner hexagon, a club shape, a pentagon and so on. Countersunk bolts are generally used as building parts.

 
2. Head shape

• Flat head bolts: The head of the bolt is a flat surface with no taper or slope. This design makes the head of flat head bolts parallel to or slightly protruding from the surface of the connecting part, but does not form a depression.
• Countersunk Head Bolts: The head is a 90 degree cone, similar to a common wood screw. This cone design allows the countersunk head bolt to sink under the surface of the connection after installation, creating a flat appearance.

3. Different contact surfaces
Flat head bolts and work-piece contact surface for the bit plane, countersunk head bolts for the bit cone.

4. Different force size

• Flat head bolts: Due to its larger head area, the stress is dispersed when it is subjected to force, so it has a higher load carrying capacity. In scenarios where large loads or vibrations need to be borne, flat head bolts may be more appropriate. Flat head bolts are subjected to large forces.
• Countersunk head bolts: Countersunk head bolts may be more susceptible to stress concentrations when stressed due to their head design, which makes their stress area relatively small. However, since countersunk head bolts are usually used to connect tight parts, their stress situation is usually more stable. Countersunk head bolts are less stressed.

          
                                 Countersunk bolts                                                                       Flat head bolts

5. Different combinations
Flat head bolts can be used in combination with flat shims, while countersunk head bolts can only be used in combination with shims with a taper.

6. Different ways of use
Flat head bolts can be deep countersunk holes or exposed, but countersunk head bolts are usually only in countersunk holes.

7. Ease of installation
Installation of countersunk head bolts is relatively more complicated, requiring pre-punched holes in the connecting parts and ensuring that the size and shape of the holes match the heads of the countersunk head bolts. However, once installation is complete, countersunk head bolts are able to maintain the flatness of the connection surface, improving the overall aesthetics.
Flat head bolts are relatively simple to install by simply threading the bolt through the connecting
component and securing it with a nut. However, due to the higher head of the flat head bolt, it may protrude from the connection surface, affecting the overall aesthetics.
 
In summary, countersunk head bolts and flat head bolts have significant differences in structure, use and characteristics. When selecting and using them, it is necessary to choose the appropriate type, material and specification according to the specific application scenarios and needs.