I saw this set of gauges -

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=5649

Looks like you set the gauge then use a measuring tool on the gauge. Question is, assuming I'm measuring an irregular cylinder, how do I get the gauge out while retaining the setting? Seems I have to disrupt the setting and count turns (lose precision) or risk scratching the cylinder. What am I missing?

Thanks,
Sixto
93 300SD

To use these gauges select one that has the range of your bore dia. Loosen the handle, push in the two ends together (only one actually moves), insert it into the bore, make sure that the handle is vertical to the centerline of the bore, loosen the handle which will allow the end to spring out to the bore's dia., tighten the handle, cock the tool sideways slightly, and slide it out of the bore. Measure the gauge length with a micrometer and that will give you the dia.

Kip's right about the procedure, however, if you are looking for an out of round condition or a tapered conditon, you'll be there forever in a vailant attempt to get some hard data. Each measurement requires you to remove the tool and measure it carefully with a micrometer.

Far better would be an inside bore gauge that has the dial already attached to the unit. You set it in the bore.......seek out perpindicularity.......and read the dial. Then you move it up or down the bore..........or twist it 90 degrees.........and measure again. You can get 20 measurements on the bore within 10 minutes. With the Harbor Freight tool, 20 measurements will take you all day.

Sure, the Harbor Freight tool is a fraction of the price, but, what's your time worth?

Brian,

You're right, but I don't think HF offers such a gauge. Personally I wouldn't mess with the bore gauges offered by HF, esp. if one is taking the time and expense to rebuild an engine.

Agreed, a decent bore gauge will probably set you back over $100. but, it's worth it.

I recently had the pleasure of using a professional gauge that is setup to read an I.D. It's set properly on size blocks and each line on the dial is .0001". I could accurately determine the out of round condition on a brand new piece of tooling that I had made. It was .000050". This was the accuracy of the grinding spindle and/or the slight change caused by the installation.

Such a gauge is about $1200. but, you get what you pay for.

$1200 will buy me new 603.97 rods and pistons

The trouble with $1200 tools is you have to know how to use them. I know a guy with machine shop connections who offered his services to measure out the block. He's also a 603 guy so I have his attention.

Sixto
93 300SD