Surface finish on CMM

[Schrocknroll]

Has anyone ever tried to measure surface finish with a scanning head using a .3mm ball? We want to measure the surface finish of a dovetail slot, which is hard to measure all the way around with a standard profilometer.

Any thoughts?

[cmmguy]

Tactile surface roughness tests at a minimum, require a .0001" radius stylus and more resolution/accuracy that your scanning head will ever possess ....

You can make a mold with facsimile and then use a profile tester to test that mold - the tester must have the ability to reverse the profile data.

[JamesMannes]

What cmmguy said. Have you used a .3mm stylus before? Do you know what they look like? I just got done using one and I couldn't wait to get that thing off off my module. It is so tiny I would have to believe that any drag scanning as done with an SP600 or SP25 would bend that immediately. Just my .02

[bw_bob]

I use .3 quite a bit. You look at that thing wrong & it falls off. If you have to drag it I don't think it will work.

[Gregl]

.3 will break in a heartbeat, last place I worked at my boss broke the first 1 in his first 10 minutes.

[Schrocknroll]

Thanks for the response. I know it won't be a proper reading, but I think they want to see if it even comes close to measuring anything worthwhile.

BTW, I'm actually using a VAST head on a Zeiss and the scanning pressure is fully adjustable. I'm sorry for posting the question here, but I've yet to see a more experienced group of professionals.

I've never had the pleasure of using a scanning head on our global, so I can't even compare.

Thanks for the quick response.

[cmmguy]

Thanks for the response. I know it won't be a proper reading, but I think they want to see if it even comes close to measuring anything worthwhile.

BTW, I'm actually using a VAST head on a Zeiss and the scanning pressure is fully adjustable. I'm sorry for posting the question here, but I've yet to see a more experienced group of professionals.

I've never had the pleasure of using a scanning head on our global, so I can't even compare.

Thanks for the quick response.

It was a fair question that should be aired. Adjustable or otherwise, there is no CMM scanning head capable of the resolution or accuracy to measure roughness. And there is no comparison to standard methods do in large part to the radius differences. That is why non contact methods are still not perfected yet.

Just the call out alone of 32Ra Microinches is equal to .8 microns.

[craiger_ny]

You would have to scan the peak and valley heights as well as the distance between along with the number of each in order to calculate the root mean square.

I can't imagine that it will work out too well corelation wise.

Craig

[Farmer]

I wouldnt go down this avenue. Surface roughness is a very precise science. A suitable tool should be used.