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Measuring an external radius

ncsteinb

Plastic
Joined
Apr 3, 2019
Location
Saginaw
What are the methods for measuring (within 25µm) an external radius? Spec is R2.5 - R3.0mm.

Annotation 2020-08-21 103824.png

I know a CMM with a scanning head can do this reliably, but what other methods are used and how accurate are they? Will they pass a Gauge R&R @ 10% or less?

Thanks.
 
I made this "gadget" years ago and if it can be used just copy.

If the picture is hard to see I can send it as a PDF file to an email.

CandR - Kopi.jpg
 
Yes I agree talk to your customer and find how they are going check your work. I have heard so many nightmare stories about differing methods of QC measuring leading to you measure it one way, it is good. They measure a different way... and it ain't.
I know some guys are thinking this makes me look like I don't know my ass from my elbow. I look at this way if I where the customer and the shop called with that question it would indicate a couple things. Shop wants give me what I want, pride aside, they want me to be happy and provide me with right part first time.
 
So you don't have a optical comparator.
Look into buying one. , It makes it easy to verify radius, lengths, diameters
Weird contours.
Also buy two part dental cast. Mix it and apply it on radius. Or other features.
Next best is a set of radius gages.
 
Also forgot to add make a go & no go radius gage from sheet metal 1/2 hard flat stock. Mill it or grind it.
 
What are the methods for measuring (within 25µm) an external radius? Spec is R2.5 - R3.0mm.

View attachment 297360

I know a CMM with a scanning head can do this reliably, but what other methods are used and how accurate are they? Will they pass a Gauge R&R @ 10% or less?

Thanks.

why in the world, do you need an R&R on a radius?

and if you do this requires a laser scanner, only way
 
Yes I agree talk to your customer and find how they are going check your work. I have heard so many nightmare stories about differing methods of QC measuring leading to you measure it one way, it is good. They measure a different way... and it ain't.
I know some guys are thinking this makes me look like I don't know my ass from my elbow. I look at this way if I where the customer and the shop called with that question it would indicate a couple things. Shop wants give me what I want, pride aside, they want me to be happy and provide me with right part first time.

Yes, that sounds like a good idea. I had always thought that asking the customer how THEY do things would just open the door for looking like "I don't know my ass from my elbow", but I guess maybe it's not interpreted that way.

We have multiple methods here: Radius gauges, MANUAL CMM (if I had a "big boy" CMM I wouldn't be asking), and shadowgraph to name a few. I'm just curious about any other techniques for measuring features like this. I can't be sending a part to CMM or shadowgraph out of every 10 pcs. I do like that caliper gadget for At-the-machine inspection.

Thank you all for your replies.
 








 
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