Measuring inside grooves

[tom_d]

Use an inside spring caliper to measure the diameter. Expand it so it just touches the widest point, compress and pull it out, let it expand again and measure it with a mike or dial/digital caliper.
For the width, you could buy a $15 digital caliper and cut off the outside jaws to fit it in the tube.

https://www.ebay.com/itm/15218000550...sAAOSwdzVXlTwM

+1 for the inside caliper. Been doing it this way for many years. Takes a little bit of feel to transfer the measurement to the outside mics, but practice first with a known dimension helps to get it right. Too help with accuracy and repeatability I put a drop of service removable locktite thread sealant on the caliper screw first. That helps to hold the caliper nut in position once set but still allows for slight adjustments.

[JRouche]

For width would a gage pin work? Or is that more work than needed? Gauge block? JR

[Captain K]

i think either would work, but I have neither. On that note I suppose I could use an adjustable parralell, which i do have.

[darryl]

Somewhere I have a piece of square stock which I cross drilled and then drilled and tapped one end for a set screw. I used a single roller from a defunct U-joint bearing as a cross pin. Hold the tool against the inside of the bore, push the pin to touch the bottom of the groove, tighten the set screw. Then pull it out and measure the extension of the pin with a conventional caliper.

I rounded over the side of the square piece so it would lay touching the bore for any bore 1 inch or larger. That eliminates the error caused by the curvature of the bore. Simple, and it works well for me.

To measure the width of the groove I used a piece of material that I think was .030 thick. Hold it against one edge of the groove and measure depth from the end of the bored piece. The put the shim against the other edge of the groove and measure again, adding .030 to the measurement. Calculate the width of the groove. I used the depth measuring ability of a normal caliper to do this. Takes a bit of finesse to hold the shim squarely, but a little care takes the error potential mostly out.

[JRouche]

To measure the width of the groove I used a piece of material that I think was .030 thick. Hold it against one edge of the groove and measure depth from the end of the bored piece. The put the shim against the other edge of the groove and measure again, adding .030 to the measurement. Calculate the width of the groove. I used the depth measuring ability of a normal caliper to do this. Takes a bit of finesse to hold the shim squarely

Oh yeah, I have five hands now

Gage pin. I have a bunch of them, they were cheap. I have a 1000 pins. For that job I would use them as Go or No Go pins. JR

[old mart]

At my firm, we had every type of measuring device imaginable, but also, a supply of the fast curing rubber used by dentists for impressions. When it cures there is very low shrinkage, and it was very good for the inspection department to use where anything else was considered unreliable.

[Bented]

Oh yeah, I have five hands now

5 very small hands as well (-:

[JRouche]

5 very small hands as well (-:

Yes Sir. Very small to get in them tight spots. Like a bore JR