The handheld welding head for laser welding machines consists of the following key elements:

1. Focusing Lens: The focusing lens is responsible for concentrating the laser beam onto the welding point. It ensures that the laser's energy is focused to a small spot size, resulting in high power density and efficient welding.

2. Nozzle: The nozzle surrounds the focusing lens and serves multiple purposes. It protects the lens from spatter and debris generated during welding and also helps to maintain a stable and consistent flow of shielding gas around the weld area. 

3. Adjustment Mechanisms: Handheld welding heads often have adjustment mechanisms to control the focal length of the lens or the position of the nozzle. These adjustments help fine-tune the welding parameters to achieve optimal welding results based on the specific application.

4. Beam Delivery System: The welding head is designed to efficiently deliver the laser beam from the laser source to the focusing lens. This involves using fiber optic cables for fiber lasers.