Butt weld is a type of joint where two plates are joined together along their edges by welding. The thickness of the butt weld is an important parameter in welding design as it determines the strength and stability of the joint.

The actual thickness of butt weld as compared to the thickness of plate is usually more. This is because the welding process involves melting the edges of the plates together to form a joint. During welding, the molten metal fills the gap between the plates and solidifies to form the weld. The volume of molten metal required to fill the gap between the plates is greater than the volume of metal in the plates themselves.

Therefore, the actual thickness of the welding material is greater than the thickness of the plates being joined. The amount of additional material required depends on the thickness of the plates and the welding process being used. In general, thicker plates require more welding material to form a strong and stable joint.

In addition to the thickness of the welding material, other factors such as the type of welding process, the welding position, and the welding speed can also affect the final thickness of the butt weld. For example, some welding processes may require multiple passes to form a strong joint, which can increase the thickness of the weld.

In summary, the actual thickness of butt weld as compared to the thickness of plate is usually more due to the volume of molten metal required to fill the gap between the plates during welding.