Cross hatching is the series of intersecting scratches on the surface of the cylinder that are used to help the piston rings seal the compression/combustion pressures in the chamber above the piston. While they are scratches they are very controlled in depth/width and angle.
Depth/Width: can range 10 to 35 micro-inches (.000010"-.000035") This needs to be deep to be able to retain oil so the piston rings have a surface of oil for sealing and lubrication. The pistons rings do not actually touch the metal of the cylinders it rides on a thin film of oil that supplied by the cross hatching. The width is usually a function of the depth the deeper the scratch the wider it is.
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One of the biggest misconceptions about cross hatching is related to purchasing a used engine. Too many times someone buys an engine block or engine assuming that the cross hatching that they see is an indication of "No wear" this is absolutely not true. Cylinders can massive amounts of ring wear and still have what looks like cross hatching. The best way to measure for cylinder wear is with a dial bore gauge and actually gauge the cylinder in at least 4 locations. Two measurements 90 degrees offset at the top and bottom. Use the largest amount for the actual bore diameter.
If you ever need help in measuring and you're in our area don't hesitate to call on us.
North Texas Speed & Machine your OEM and Performance engine rebuilder. (972)221-8811
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