Measuring small bore contours....

[quizzical1]

Hi All,

Is there an accurate non-destructive (without cutting in half) method available to measure small bore profiles including the angles and radii?
We have tried dental impression compound to get a shape to look at on a comparator and 3D microscope (limited depth-to-dia ratio) with some success.
Our CMM can't read the radii accurately. Someone mentioned CAT Scan possibly?

TIA

One profile in particular is a

 

[3DDave]

If it's metal there is an alloy used for matching gun chambers that shrinks upon cooling and than undergoes a phase change to recover that size in a short time after. Pour it in, wait until it shrinks and then quickly remove.

https://www.rotometals.com/chamber-casting-alloy-ingot-aka-low-158-190f/

 

[btrueblood]

There are specialty waxes and RTV compounds with near-zero shrinkage also. Check out Reprorubber.com, among others.

You should be able to inspect the contour with bore gages mounted on an axial stage also. We used to use the EDM machine to pick up fine radii and corners in deep bores.

 

[HGMorgan]

A CMM will not give good results measuring a radius that is less than 90 degrees.
Instead of taking 3 points and trying to output a radius, take 3 point vectors and review the results.
Think of it as inspecting a small contour.
Example: take 3 point vectors on the R.060.
If all 3 points are -.001 from nominal, the radius is .059 & C/L is 0 (pretty much improbable, this is an example).
The actual points can be reviewed to determine the actual condition.



Harold G. Morgan
CATIA, QA, CNC & CMM Programmer

 

[quizzical1]

Thanks Guys!

I appreciate and value your input.
Yes, the part is metal (303 SS).

Would CT scan be worth looking into?

 

[btrueblood]

CT will give you fairly granular images and artifacts that become difficult to interpret; we could only get about .05 in. or poorer resolution. But, it never hurts to ask (and it's been 20 years since I did work with a local shop that had industrial CT scanning equipment, so that first statement may not be valid anymore).

 

[MintJulep]

First, ask yourself "how important is it?" Do any of those features really affect the function.

How many of these are you making? What is the process?

Maybe something like

https://www.vision-systems.com/fact...-3d-imaging-enables-highspeed-bore-inspection

(That was the first hit for "interferometry bore inspections" but there are others)