Al, I haven't been able to find this gage on ebay - the range needed is 568-978. There was one with a larger range there however, so I will keep looking. Have added it to my "Favorites"
Ron, in a way this is a new requirement. We made a very similar part for this company for a number of years, but they recently made a design change. It was through the PPAP and control plan that they realized we use a plug gage for the ID, which we do for most parts since the ID is a tool dimension. I rather doubt they will absorb the cost at this stage, but it is a consideration if they insist on it.
Wes, this is in part their explanation for the use of a "digital" gage - nothing to do with uploading the SPC data. We don't have the capability to do that regardless.
The reason I suggested digital is resolution. I have never seen an analog metric gage with 0.001mm resolution; the most I have seen is 0.01mm. A vernier IntraMic probably has more, but they are difficult to use and read, have limited range, and are not really inexpensive.
The reason resolution is important is: if you take your natural process variation on the bore, which on your submitted capability study looks like 0.033mm at the most, an analog gage would give you three different measurements. Three possible values is not enough; a rule of thumb is to measure with a gage that has resolution at least 1/10th of your process variation. The reason is that the data most of interest in a study is in the tails of the distribution, which would not be visible in a data set with only three classes; and even the mean is hard to estimate with only three classes of data. The gage I suggested has 0.001mm resolution (by the way, the discrimination of a gage will be less than the resolution) which would give 30 possible different measurements which would work well sorted into 10 classes for analysis. I did notice that the capability study you submitted has only three classes of data, although I only got the graph, so I don’t know what your data resolution was.
The reason I suggested that particular gage is: flexibility: it has a one inch range, and more heads can be purchased to extend that; ease of use: the way the three contacts work make it difficult to get a bad measurement; and considering that it comes with the set rings, it really isn’t all that expensive.
Thanks for the help you've provided,
Sue