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Number of Contact Points Required
I have seen quite a bit of debate on here concerning the number of hits to take for the measurement of plane, line, & circle features. I have been following a NPL (UK) Measurement Good Practice Guide for the last couple of years and I feel has helped me tremendously in my precision and repeatability of measurements and thought I would share it with all of you who have helped me through the past couple of years in my transition from MMIV to PC-Dmis. It goes into quite a bit of detail concerning the number of recommended hits and also goes into detail about the distribution of hits beginning on Page #25 of the GPG No. 41 titled CMM Measurement Strategies.
I've never heard anyone on here mention any of the NPL guides, but on this website: http://www.npl.co.uk/length/gpg.html, there are several guides that are very helpful to beginning and advanced metrologists. I haven't had time to go through all of them but at first glance some of them look extremely helpful. I think we paid $40 for each one of the guides a couple of years ago but now most of the guides are being offered for free.
The main link for the NPL Measurment Good Practice Guides is located here at:
http://www.npl.co.uk/publications/good_practice/.
I've never heard anyone on here mention any of the NPL guides, but on this website: http://www.npl.co.uk/length/gpg.html, there are several guides that are very helpful to beginning and advanced metrologists. I haven't had time to go through all of them but at first glance some of them look extremely helpful. I think we paid $40 for each one of the guides a couple of years ago but now most of the guides are being offered for free.
The main link for the NPL Measurment Good Practice Guides is located here at:
http://www.npl.co.uk/publications/good_practice/.
I've been in the machining trade 25+ years and Inspection 3+. Working
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