Spot facing is a mechanical drilling, or milling, process. After the initial hole is drilled, a larger well, or recess, is drilled into the material. The head of the screw or nail fits into this well. This allows the nail or screw to sit flush with the surface of the item that is drilled. This term is also spelled as spotfacing and spot-facing by machinists and parts manufacturers.
This technique can be used on a variety of machine and woodworking projects to ensure a smooth, professional finish. Furniture makers often use it to hide nails and screws. Machinery with working parts also uses spot facing. This can help ensure that the heads of any nails, screws, or bolts do not get in the way of the moving parts.
Both professional and do-it-yourself carpenters and machinists can use spot facing. When working with wood, this process is also known as counter-sinking, or double-sinking, a nut or screw. Amateur carpenters generally use drill bits of different sizes for counter-sinking. Professionals often use a special one-piece drill bit to do this.
Spot facing, also known as counter boring, can be forward or backward. In forward counter boring, the well is drilled on the top surface of the object being drilled. Backward counter boring involves drilling a well on the underside of the object that is drilled.
The term spot facing is sometimes used to identify a specific type of counter boring. Some machinists use the term to refer to working with an object that is not flat, or has been cast in metal. For example, when drilling an object with an angled or round surface, that is referred to as spot facing.
Specialty tools, called counterbores, can be purchased to make this process easier for a machinist. These tools are usually referred to as spot facing cutters. Generally, these are metal, rotating drill bits with cutting edges that match the size of the hole to be drilled or milled.
The counterbore is attached to a drill press. It rotates in the drill, while the object being drilled remains stationary. When the drilling process is complete, a smooth hole with the well either on the top or bottom of the object, is ready for a nut, bolt, or screw to be inserted.
Counter boring tools are available from several manufacturers for specific drilling needs. Tools can be specialized to do forward or backward counter boring. Combination tools are also available that do both types of work.