• Valve-grinding tools are used on truck or car engines.Large engine maintenance image by Alexey Stiop from Fotolia.com
  
  Valve grinding is used primarily to cut and smooth out automobile engine valves, which sit in the core of the motor. The tools used to cut these cores or cylinders out and then smooth them have developed considerably over the years.
  
  

Cutting Tools

• The first step in grinding a valve is to bore the hole in the engine core to make the valve cylinder. The hole can be four, six, eight or even 10 cylinders, depending on the engine manufacturer. A variety of cutting tools are required to bore these valve cylinders. Each hole bored begins with a small diameter hole and is increased to the desired diameter. Drill bits are attached to a press to make the initial cuts. The drill bits can be diamond-tipped or carbide-tipped for strength and cutting fluid is poured over the bit as it is boring into the valve cylinder.
  
  

Abrasives

• A grinding wheel is attached to the end of the press to smooth out the valve cylinder. This abrasive material is similar to the grains of sandpaper, but made of a hardened material such as cubic boron nitride or diamonds. The abrasives become finer as the valve is smoothed. The grinding tool is round and has a bit attached to the center so the abrasive can be attached to the machine used to rotate the grinding tool. Lubricant is poured onto the grinding tool as it is being used to smooth the valve cylinder, to prevent heat from building up and cracking the engine core.
  
  

Finishing Tools

• Once the valve cylinder is bored and ground, it's necessary to finish the valve cylinder to the desired diameter. The valve-grinding tool used to finish this machining process to the valve cylinder is a valve seat finishing device. It uses finishing abrasive to grind the valve to the desired diameter to within hundredths of inches. The gap between the valve head and valve cylinder is minute, but must be enough so the lubricant, such as oil, can be pressed up into the valve cylinder and between the valve head to prevent wear and overheating.