I was out at my former workplace today and I asked if I could borrow a 0.001mm micrometer so I could check some of my mics and callipers. I also borrowed a Mitzi digital calliper while I was at it.

It's not what I would call a rigorous test which would involve a greater degree of cleanliness, some attempt at temp stabilised and maybe some repeated measurements

Here is what I had to play with
IMG_3309.jpg

X is the Fowler 0.001mm mic from Work.

A is a near new 150 mm ebay digital calliper that I use in my electronics space.
B is a 150 mm, 6 year old calliper I bought from H&F and is my general shed calliper - they are pretty beat up and the adjustment roller wheel has vanished after I have dropped it several times, but it keeps on working.
C is a second hand 0-2" 0.001" Mitzi mic I picked at a HTPA sale. It was pretty rusty and appropriately priced.
D is a new 300 mm ebay digital calliper I keep in my shed but I don't use it much.
E is another H&F special that I picked up during a sale. It has not been the same since I dropped it. The readout occasionally jumps without warning and so I cannot always trust it on a single reading but if I keep re-zeroing it eventually it gives something close to the true value,
F is a near new 25mm 0.01mm Mitzi that I use in my shed.
G is a 200 mm 5 year old calliper that I use a lot in my shed - It's the one I usually keep near my lathe/mill
H is the Mitzi digital calliper I borrowed from work.

For small measurements I measured individual feeler gauges while for larger measurements I used parallels. I tried as best I could to make sure the measurements were all done in the same spot on the feeler gauge or parallel but maybe I did not succeed and this may explain some of the scatter of the results.

All measurements smaller than 25 mm are referenced to the Fowler Mic and the one measurement larger than 25 mm (M) is referenced to the Mitzi calliper.

(G) is a grouped set of ~6 feeler gauges to generate something thicker, I was not too careful about cleaning these so that could have contributed to the scatter.

I was quite amazed to see that up to 25mm, apart from those G measurements, they all clustered close to the +/- 0.01mm.
Where you don't see all 8 points it means that means points are underneath others.

MicandCallipers.jpg

I should add that this level of reproducibility may not be achievable in a workshop situation when measurement surfaces may not as flat/smooth as feeler gauges or parallels, or one is in a hurry, dirt etc.

When I get a chance I will explore the 25 mm and upwards range a bit more.
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