Measuring an ID with gage blocks (not gage pins)

[Bill Kahn]

So we’re trying to measure a round hole with a square block

That is funny! Thank you. And, yes, that is exactly what I did. And, while most of my bright idea work-arounds for lack of talent/lack of experience/lack of funds fail, this stacking gage blocks to measure an ID accurately turned out to work quite nicely for real. I have a much reduced need for a set of gage pins now. Though getting better with my snap gages is still on my list. -Bill

 

[martik777]

When I know I'll be boring several same-sized holes I make a tapered plug gage, then use my outside calipers (or mike) to mark it with the location of the ID I'm shooting for. It doesn't take much time or material to make one. Two marks for your acceptable min/max ID and you have a go/no-go tester. I'm talking a Sharpie mark, not scribe lines, so there won't be raised edges from the scribing.

I make a 2-ended plug, one is .010" under size and the other .005" but I like your taper idea - will try on the next batch

 

[epanzella]

I feel that going thru all kinds of extraordinary measures to avoid learning how to use telescoping gauges is counter productive. I keep the bottom of the gauge near my end of the bore with top locked and tilted in so it is over extended. The I rotate the top of the gauge towards me until it falls out of the bore. At some point during that arc it was in the right place. Do this only once then measure. Being a ham fisted guy with one compromised hand I don't tighten my mic against the gauge but rather get close and then close it a little at a time while swinging the gauge thru. This prevents me from accidentally compressing the snap gauge. I can get at least .001 repeatability. Practice until you get 3 identical readings in a row. It's more a question of feel rather than getting more information. When measuring holes too small for a tel gauge I use the drills in my drill index. Between decimal, metric, letter and numbered drills I can get within a few thou of just about any hole from 0 to .5" Pin gauges are on my list but so is about a million dollars worth of other stuff!

 

[Lo-Fi]

Here's my telescope gauge process:

Compress and lock
Insert with anvils 12 and 6oclock, tail pointing 5 or ten degrees up from horizontal
Release. Lock lightly.
Push down on the tail, catch carefully as it exists the hole.
Measure with the mic in one hand and gauge in the other. Rock the gauge inside the mic anvils adjusting the mic until slight resistance is felt over the widest point over the gauge anvils. Do not run the mic down onto the gauge, you'll likely lose your reading.

If you faff about trying to get centered, the tail totally inline and whatnot you'll never get a decent reading. The "over center" method is pretty foolproof, repeatable and naturally finds the sweet spot just because physics says so.

 

[Trillobyte]

It's something you get a feel for. I can work to a couple of thou with decent verniers, tenths with snap gauges. Did take me a while to get good technique, though.

If you want some pointers on excellent snap gauge technique, look at some of Abom79's old videos on YouTube.

Once you get good technique, it's really hard to not be accurate and quick with snaps, but I applaud the ingenuity with the blocks!

Thanks for that Abom79's suggestion