what is this stuff called

DUSTY NOGGIN

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i watched a gunsmith use a little strand of what looks like - 30 lbs mono filament fishing line

it was used for measuring gaps in hard to reach or otherwise un- measureable areas ... like bolt head clearance

when smashed between 2 surfaces it stayed flat & once that flat reached a certain width , it resulted in a measurement

what is this tool / product called ???
 

pawater

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Its called Plastigauge, I seen it used once many years ago (30+) when I was helping my Dad rebuilt an Inline diesel in a big truck. You can find it online. It is used widely in the automotive industry. I believe they used it to put under the head at the cylinder sleeve to see if the sleeve was seated correctly before final assembly. However I think it is used to check main bearings and many other things.
 

therifleman556

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I believe they used it to put under the head at the cylinder sleeve to see if the sleeve was seated correctly before final assembly.

I can't say definitively that it's not used this way, but I've never seen or heard of it used in this fashion. Usually all one does is starts with fresh counterbores and uses a dial indicator to measure liner protrusion on big diesels, or piston height for determining head gasket thickness in smaller engines.
 

pawater

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I can't say definitively that it's not used this way, but I've never seen or heard of it used in this fashion. Usually all one does is starts with fresh counterbores and uses a dial indicator to measure liner protrusion on big diesels, or piston height for determining head gasket thickness in smaller engines.

Probably so, like I said it was 30+ years ago, I was maybe 12 and an old school Mechanic was leading the pack.
 

Mooseknuckles

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When I was in diesel school they had us use it to measure clearance on rod bearings. Back then a bearing roll out was a common practice. Roll out the old ones, roll in new bearings.
 

bigedp51

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The problem with using Plastigauge to determine head clearance is it must be used on a smooth flat surface. Meaning it must be used on a flat smooth headspace gauge and not a cartridge case with writing on its base.

A simpler way to measure head clearance is to use a fired spent primer. You measure a case from the case mouth to its base and write it down. Next you start the fired spent primer into the primer pocket just using your fingers. Now chamber the case and let the bolt face seat the primer and then measure from the base of the primer to the case mouth. Now subtract the first case measurement from the second and this is your head clearance. Meaning how much shorter the case is than actual chamber headspace.

HK76WCp.jpg
 
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