.0005" bore graduation ok for measuring bores?

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My concern is 3.4252-3.4256 is the new spec, service limit 3.4279 for cyl bore size. How well would a .0005" graduated bore gauge work? Could I zero the gage (using the mic) at the spec, and after getting the initial reading, zero the gauge -.0005 away from that reading and work my up to the reading by zeroing the gauge .0001 up each time?
 
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What application are we talking about? I think you can probably get by with that bore gauge- people estimate ten thousandths all the time on mics that are graduated in the one thousandths. I think you could probably do much the same with that bore gauge. Not sure exactly what you mean by zeroing the gauge .0001 up each time- are we talking about a dial bore gauge? I'd just zero the gauge wherever its convenient, watch the dial and do the math. Also, I've seen often enough when metric specifications are converted to inches for us fatstupidamericans, they generally list the specs to a .0001 precision- whereas a similar american engine will use .001 increments. I suspect that listing specs in .0001 increments has more to do with avoiding rounding error than actually approaching space-shuttle tolerances. I mean- you have .0027" to work with here.
 
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If you can get your bores to .0005" of what you are shooting for, you have done a very good job. A good final surface finish is probably the most important thing , and a straight non tapered bore. And I say again, the proper final finish of a cylinder bore is critical.
 

vinu_neuro

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This is pre-machining. I want to check the roundness/taper. Reason I'm concerned about the .0005 graduation is that the 'new' spec is 3.4252-3.4256. Service limit is 3.4279.
 
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 Quote:
Also, I've seen often enough when metric specifications are converted to inches for us fatstupidamericans, they generally list the specs to a .0001 precision- whereas a similar american engine will use .001 increments.
His specs translate to 87.00/87.01mm new, 87.07mm max wear. That's tighter than 0.001 inch increments but at least the numbers don't look like they were generated by a random number generator.
 
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 Originally Posted By: mechtech2
If you can get your bores to .0005" of what you are shooting for, you have done a very good job. A good final surface finish is probably the most important thing , and a straight non tapered bore. And I say again, the proper final finish of a cylinder bore is critical.
Honda bore clearance on some engines is .0008. If you are .0005 off on that baby you are in trouble. Honda sets standard clearances on a NASA standard day.
 
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Smokey - Valid point. My Ford piston clearance is spec'd for .0004" to .0012 when new. It is very tough to machine cylinder bores like the factory does nowadays. I still believe getting to .0005" is good work.
 
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