How to best measure angle at end of bore?

[AmericanMachinist]

How would you best measure the angle of say the taper on the inside of a female flare fitting? About 3/8" bore ID.

Thanks

 

[MrWhoopee]

Assuming some sort of commercial fitting, I'd try to determine which and search for the specs. Barring that, grease the inside and pour in some plaster of paris. There may be better choices, wax, cerrobend, but you get the idea.

 

[Alexander McGilton]

Is this the item you're thinking of? In a production setting I would make a Go and No-Go gauge. A set of thread and taper fittings in hard steel, all with various taper conditions of too steep or too shallow. Thread them in to a specific torque, and should they protrude excessively or insufficiently than the taper is seating incorrectly.

 

[Jim F]

 

[RJSakowski]

An instructive video. Rather than go through the math, I will opt for drawing it out in SolidWorks (or other parametric CAD program). After setting the known constraints and dimensions, the desired dimension pops out as a driven dimension. When setting dimensions is production drawings, I would specify a ball as a metrology tool for Q.C. accurately assessing the part geometry.

The video doesn't address the OP's original concern of accurately measuring a small angle. This is a much more complicated procedure which can be done using a similar strategy as in the video but with two different ball diameters. The math becomes considerably more difficult but the SolidWorks approach will handle it nicely. However, when dealing with small features, even a micrometer accurately measuring to .0001 isn't sufficient to accurately measure an angle.

IMO. the best approach is to use bluing with mating parts or machined go/no go gages. With careful work you should be able detect surface deviations on the order of a tenth of a thousandth which is probably good enough for most purposes.

 

[Jim F]

An instructive video. Rather than go through the math, I will opt for drawing it out in SolidWorks (or other parametric CAD program). After setting the known constraints and dimensions, the desired dimension pops out as a driven dimension. When setting dimensions is production drawings, I would specify a ball as a metrology tool for Q.C. accurately assessing the part geometry.

The video doesn't address the OP's original concern of accurately measuring a small angle. This is a much more complicated procedure which can be done using a similar strategy as in the video but with two different ball diameters. The math becomes considerably more difficult but the SolidWorks approach will handle it nicely. However, when dealing with small features, even a micrometer accurately measuring to .0001 isn't sufficient to accurately measure an angle.

IMO. the best approach is to use bluing with mating parts or machined go/no go gages. With careful work you should be able detect surface deviations on the order of a tenth of a thousandth which is probably good enough for most purposes.

Some of us don't know CAD.

 

[RJSakowski]

Some of us don't know CAD.

Then you best know math