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Old 02-23-2013, 12:11 AM   #1
OC_Nooby
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Member#: 311781
Join Date: Feb 2012
Location: Canada
Vehicle:
2003 WRX w STI V8

Default How do you set a 2 point bore gauge inside a cylinder for proper reading?

Hey Guys,

So I want to measure my bores but I'm confused on how you set the bore gauge inside the cylinder. The tool I'm using is a Telescoping Gauge and Micrometer to read the measurement.

What I'm trying to ask is how do you set it so its sitting 100% in the middle to get the absolute best reading? How do I know I'm not at a slight angle or that the tool is in the middle? I know I want to take the measurement 1-2 inches below the top of the cylinder but that's about it. I might not have the right tool but in general even the bore gauges are the same (2 point) but they give out a reading. I'm manually doing the reading with the micrometer.

I put bore gauge in the title so that I get more hits on the thread. I have a telescoping gauge that I lock then read with the micrometer. Micrometer is calibrated.

Just trying to figure out a solid way to measure I'm new to this. I will want to take a few measurements around the bore but not sure how to get consistent measurements.

Thank You
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Old 02-24-2013, 05:40 AM   #2
minifreak
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First you loosen the telescoping gauge to allow it to fully extend and insert it at an angle into the bore, tighten up the knob so it will not extend any more and start to pivot on one of the prones until you are passed vertical. Lock it up some more and take the measurement using your mic.

If done correctly it will hold the largest allowable distance (diameter)
_____ _____ _______
__\__ => __|__ => ___/___

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Old 02-24-2013, 05:41 AM   #3
minifreak
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Member#: 116914
Join Date: Jun 2006
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Location: Beautiful British Columbia
Vehicle:
2006 WRX Wagon
Obsidian Black

Default

First you loosen the telescoping gauge to allow it to fully extend and insert it at an angle into the bore, tighten up the knob so it will not extend any more and start to pivot on one of the prones until you are passed vertical. Lock it up some more and take the measurement using your mic.

If done correctly it will hold the largest allowable distance (diameter)
_____ _____ _______
__\__ => __|__ => ___/___

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Old 02-26-2013, 08:37 PM   #4
OC_Nooby
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Default

Thank you! I moved on to a bore gauge, a tad easier. The telescoping gauge was a learning experience non the less!

Thanks again!
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Old 02-27-2013, 10:39 AM   #5
kpluiten
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The telescoping gauge (T-shaped snap guage ones) are very difficult to use accurately, and most of the lower cost ones don't lock up well and will have enough slop/play in their lock up mechanism that they will compress every so slightly when you put a micrometer on them. I've seen this several times. The tendency is to then over tighten the locking mechanism to try to make them tight, but that only wears them out or gives them a "memory". By this I mean that when you measure one bore size over and over (like doing an engine block over and over), the locking mechanism tends to start to force the two extending arms into the same position as you tighten it down, probably due to grooves made by the locking mechanism similar to how a set screw acts. Again, this is very common on the cheaper ones. I'm not well versed in the expensive ones.

I did a gauge R&R test with my snap gauges and they failed. Because of this, I would NEVER build a motor with them. They are fine for other uses where you are not trying to hold a 0.0001".

I also used a nice true bore gauge after messing with the snap gauges, and there is no comparison. The difference in ease of use, accuracy, and repeatability is night and day. To build a motor correctly, I'm now a firm believer that you MUST have a bore gauge.
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