One of the most accurate ways to measure a bore is with a dial bore gage, but these can be really expensive and seldom used tools. A nice Mitutoyo dial bore gage set is almost $400 as I write this.
I loved this gadget by gbritnell I saw on HMEM to adapt a DTI to the task:
Snap gages are cheap, but take a lot of “touch” to be accurate. Dial bore gages are one of the best tools for bores, but they’re costly. These guys fall somewhere in the middle, but closer to the dial bore gage. They’ll need to be calibrated against a reference, but once that’s done, they’ll be quick and easy to use.
Dial bore gage…
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Adding a second ball tip to the moving piece will make is a true bore gauge. And eliminate the need to “find” the max ID point. It will make using a calibrated ring gauge a requirement however. As designed you can just use a Mic or caliper for calibration.
Yes , but how to calibrate. Would you not then need a ring gage?
Dan, you could use a ring gage, but you can also just use a micrometer to set an arbitrary size.
Snap gauges are very easy to use, Bob. Once you know the trick, they are simply the easiest way to measure a bore (assuming you have a micrometer in the right range).
1 Slightly angle the gauge in the bore so the spring is compressed and then tighten the friction knob until the moving face is held in place but no more. Do not lock it.
2 While moving the handle through the center of the bore, rock the handle from side to side. This will automatically align it to the diameter of the bore and once the handle has been moved over center. the gauge now represents the bore diameter to better than 0.001″.
3 Measure the gauge with an appropriate micrometer while moving the gauge enough to insure that the micrometer measuring surfaces get a ‘look’ at the radiused tips of the gauge. This insures that you do find the biggest dimension of the gauge. If the gauge ‘sticks’ in the micrometer, then the micrometer is not yet set to the measured diameter.
I can send you a video if my writeup is not clear.
Mike, no need for video, I’m quite familiar with the technique. And I also have a set of bore gages, LOL. This is just a neat tool and I’m always up for another one of those!
Where to get this, I already have the test indicators.
I use one just like it for ID and OD checking. Nice because they use very little pressure and don’t scratch thin walled parts. Always calibrate with ring gages or Joe block sets.
where can I get some like this from(already have test indicators)
t by gbritnell I saw on HMEM to adapt a DTI to the task:
where to get this, I have the test indicators, already