This should be obvious. I also know what is pretty much required when it comes to showing your inspection tools to your clients - but.. I needed a new pair of micrometers to help me measure taper in my lathe. I'm low on cash right now (bought CNC lathe, ancilliary equipment, tooling, starrett machinist's level, etc.) and need to keep the spend low. So, after looking at the mitutoyo's that I actually want for about $280 at grainger, I went and bought the $35 pittsburgh digital micrometer with a 20% off coupon at harbor freight and made my measurements.
At my 'real' job / day job we have tons of mitutoyo's which are calibrated. I took some time to have a look at the super cheapo's vs. mitutoyo's best with calibration certs that are due in 2014.
I did two tests: 1.) origin repeatability, 2.) variation between micrometers' measurements on my test parts. The data that I took is attached.
Digital micrometer evaluation 01.txt
This is a tab delimited text file which can be opened in excel.
The result is pretty interesting. As far as I can tell the pittsburgh is the best instrument for repeatability and accuracy. precision on all three are identical (0.00005")
The pittsburgh repeats it's origin within -0.00001" over 10 attempts. The most expensive coolant proof calibrated mitutoyo repeats within +0.00004" in 10 attempts.
On the second type of measurement, the pittsburgh always ended up closest to the average of the measurments - within -0.00004", while the most expensive mitutoyo ended up within -0.00012"
We're splitting less than hairs here (literally) but this really speaks to the capability of cheapo chinese manufacuters. And so what if it isn't coolant proof. I can buy 10 pairs of pittsburghs for the price of 1 coolant proof mitutoyo.
I don't want to rag on mitutoyo here - their build quality is far superior - but the data says that thier measuring capability on calibrated micrometers is actually not, and for 10x the price.
I will likely buy a pair of mitutoyos as soon as I can afford them none the less... Thought this was pretty entertaining though.
At my 'real' job / day job we have tons of mitutoyo's which are calibrated. I took some time to have a look at the super cheapo's vs. mitutoyo's best with calibration certs that are due in 2014.
I did two tests: 1.) origin repeatability, 2.) variation between micrometers' measurements on my test parts. The data that I took is attached.
Digital micrometer evaluation 01.txt
This is a tab delimited text file which can be opened in excel.
The result is pretty interesting. As far as I can tell the pittsburgh is the best instrument for repeatability and accuracy. precision on all three are identical (0.00005")
The pittsburgh repeats it's origin within -0.00001" over 10 attempts. The most expensive coolant proof calibrated mitutoyo repeats within +0.00004" in 10 attempts.
On the second type of measurement, the pittsburgh always ended up closest to the average of the measurments - within -0.00004", while the most expensive mitutoyo ended up within -0.00012"
We're splitting less than hairs here (literally) but this really speaks to the capability of cheapo chinese manufacuters. And so what if it isn't coolant proof. I can buy 10 pairs of pittsburghs for the price of 1 coolant proof mitutoyo.
I don't want to rag on mitutoyo here - their build quality is far superior - but the data says that thier measuring capability on calibrated micrometers is actually not, and for 10x the price.
I will likely buy a pair of mitutoyos as soon as I can afford them none the less... Thought this was pretty entertaining though.