Monday, October 7, 2013
Engine Valve Grinding Tools
Engine valves open and close to allow in a mixture of air and fuel for combustion, and it is important that they have a good seal for optimal engine performance. A poor seal will leak fuel into the engine and can cause heat damage to the engine. When replacing or repairing valves, the edges must be ground to fit. People began grounding metal thousands of years ago, and similar methods are implemented today. The basic principle of grinding is to rub a metallic edge against an abrasive surface, such as a rock. Modern advancements improve efficiency and quality of grinding.
Mechanics Stethoscope
Similar to a doctors stethoscope, a mechanics stethoscope allows a mechanic to listen to different parts of an engine to determine whether a repair is necessary. The noise resulting from a valve problem is a light clicking while the engine is idle. A mechanics stethoscope minimizes the difficulty in determining the necessity of valve grinding.
Coolant
Coolant must first be applied to both the valve and the grind stone, as the heat from grinding can cause the abrasive to come loose. Todays abrasives are often made with diamond or cubic boron nitride (CBM), which is a manufactured material almost as hard as diamond but capable of withstanding greater temperatures. While the diamond or CBM can withstand the heat from grinding, the mounting brackets may not be capable of withstanding the heat, so coolant is applied to reduce heat while maintaining proper friction.
Grinding Stone
Grinding stones must be specifically matched to the material being ground, so the first step before grinding is to check the type of metal in the valve. Cast iron and stainless steel have different levels of hardness, and having the wrong grinding stone can ruin both the valve and the stone. Some grinding stones will employ a superabrasive, which has greater grinding ability and shorten the time it takes to grind a valve.
Valve Seat Finishing Device
The grinding wheel and abrasive grinds the valve close to the correct size, but the finishing tool grinds within hundredths of an inch, providing the closest possible fit and allowing for a tight seal. The need for such fine adjustments is necessary because the valve head and valve cylinder must accommodate a small amount of oil to prevent engine overheating.
Prussian Blue
Prussian blue is a blue ink that is applied to a finished valve face to check the contact. Applying the ink to the valve face and then turning the face in the valve seat will show if full contact is made on all parts of the valve connection. The valve should only be turned about 1/8 of the way around, as a full turn will give a false indication of connection.
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.