How To: Measure Inside Diameter with Various Tools - Calipers, Telescopic Gauges, Inside Micrometer

[BladesIIB]

This week there were two threads going about taking inside measurements. One trying to find the best tool for it and another talking about using Inside Spring Calipers. I thought I would make a video to help those two members and maybe others. As they say a picture is worth a thousand words, I hope this video helps.

Having trouble getting the same accuracy measuring Inside Diameter (ID) as you are measuring Outside Diameter (OD), then this video is for you. I can't pass "feel" through the video but these techniques should help you develop your own feel for measuring.

Accurate measurement is the key to most machining tasks whether boring on a metal lathe or on your milling machine or just measuring parts for fit. You want to make sure your measurements are accurate.

The video has the following sections for the different tools - Where listed multiple times, they are measuring a different size bore, or setting the tool vs. measuring the tool with a mic: If you go to the description of the video in YouTube you will find actual links to each time listed.

Overview of all the tools - 1:35
Mitutoyo Digital Vernier Calipers - 3:45
Inside Spring Calipers - 6:15, 11:45, and 17:30
Telescopic Gauge - 9:05, 13:05 and 20:40
Mitutoyo 1-12" Inside Micrometer - 9:50, 13:45, and 22:00

I hope this helps you master your "feel" in accurate measurement.

 

[KevinM]

Thanks for the video. It was quite helpful to see the full process of someone measuring. I picked up a few nuggets of wisdom.

 

[BladesIIB]

Appreciate the feedback Kevin, glad it was informative.

 

[.LMS.]

I am also finding all of your videos to be helpful to me, as I am very green to all this. Thanks, and I have subscribed to the youtube channel.

I have a question about the use and accuracy of telescopic bore gauges. Given the bore is curved but the face of the gauge is not curved, it seems to me that the measurement would always be an approximation. See the crude ascii pic below for what I am talking about if the explanation above is unclear.

( [

so the paren is the curved bore, and the open bracket is the bore gauge, so the measurement is the corner of the bracket, which is always going to be less than the full inner diam (which is perpendicular to the midpoint of the bracket). I know there's a good answer since the use of these is so prevalent, but I am just not getting it.

 

[RJSakowski]

I am also finding all of your videos to be helpful to me, as I am very green to all this. Thanks, and I have subscribed to the youtube channel.

I have a question about the use and accuracy of telescopic bore gauges. Given the bore is curved but the face of the gauge is not curved, it seems to me that the measurement would always be an approximation. See the crude ascii pic below for what I am talking about if the explanation above is unclear.

( [

so the paren is the curved bore, and the open bracket is the bore gauge, so the measurement is the corner of the bracket, which is always going to be less than the full inner diam (which is perpendicular to the midpoint of the bracket). I know there's a good answer since the use of these is so prevalent, but I am just not getting it.

The faces of the gage are domed. The radius of curvature is less than the minimum range of the gage. The same is true for inside micrometers.

 

[.LMS.]

The faces of the gage are domed. The radius of curvature is less than the minimum range of the gage. The same is true for inside micrometers.

I figured it would be that or something as simple - I believe you but they sure do look flat in the video...

 

[BladesIIB]

I figured it would be that or something as simple - I believe you but they sure do look flat in the video...

Appreciate the feedback on the video and glad you are finding them helpful. I will send a pic of the end of the telescopic gauges when I get home. They are domed as mentioned above and only the tip of the gauge makes contact in the bore giving an accurate reading through the mic. The smaller gauges are smaller diameter barrels giving them as mentioned above a radius that will fit in the bore sizes they are capable of measuring.

 

[BladesIIB]

I am also finding all of your videos to be helpful to me, as I am very green to all this. Thanks, and I have subscribed to the youtube channel.

I have a question about the use and accuracy of telescopic bore gauges. Given the bore is curved but the face of the gauge is not curved, it seems to me that the measurement would always be an approximation. See the crude ascii pic below for what I am talking about if the explanation above is unclear.

( [

so the paren is the curved bore, and the open bracket is the bore gauge, so the measurement is the corner of the bracket, which is always going to be less than the full inner diam (which is perpendicular to the midpoint of the bracket). I know there's a good answer since the use of these is so prevalent, but I am just not getting it.

Here is a decent pic of the Telescopic gauges to see the shape of the ends. Much more like your paren above than the open bracket. They get notably flatter as the size increases and they will measure a larger “flatter” curve of a bore. Also the closer they match the bore they are measuring I believe that is what helps them self center. I hope this gives you a better visual.

 

[.LMS.]

Thanks for that visual