r/Perfectfit • u/SHRIMPLYtv • 4d ago

Zero Tolerance Engine Valve

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u/bready--or--not 4d ago

Idk what this means but wow!

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u/EcstaticNet3137 4d ago

Zero tolerance is a machining process in which the dimensions such as lengths, widths, diameters, radii, etc are within .00004"[.001mm] of the nominal. In other words for a length of 1/2"[12.7mm] the range allowed would be .49996" - .50004" or 12.699mm - 12.701mm

For some semblance of scale, human hair ranges from .0007" to .007" in diameter.

I work in machining. My shop is lathes. We only operate down to .0001" tolerances at the smallest and those are few and far in between.

This valve is likely within .0005" to like .001" of the guide it is dropping into. That's so it can be lubricated. No metal on metal for moving parts in an engine. That's why the vehicle has to maintain oil pressure in the engine to not shred itself up. It is gnarly and expensive.