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Thread: Testing few Mics and callipers
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19th Sep 2018, 12:10 AM #1Member: Blue and white apron brigade
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Testing few Mics and callipers
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 keep at my electronics bench.
B is a 150 mm, 6 year old calliper I bought from H&F and is my "general" shed calliper - its' pretty beat up, and after I dropped it several times, the thumbwheel on it disappeared. I also lost the battery cover on it and was using a piece of electrical tape to hold the battery in but miraculously found teh cover a few months later in a drawer.
C is a second hand 0-2" 0.001" Mitzi mic I picked at a HTPA sale about 10 years ago. It was a bit rusty and appropriately priced. It came up OK although part of the scale is hard to read. I measured it up against another Mitzi at work and at the time it was spot on across the range .
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 times 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. It's been dropped few times. It no longer turns off and so says on all the time but I only need to replace the battery in it every 8-10 weeks.
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 single ~150mm measurement (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 some points are underneath others.
NB the horizontal axis (Measurement) is shown as a log scale
MicandCallipers.jpg
I should add that this level of reproducibility may not be achievable in a real workshop situation when 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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19th Sep 2018, 03:50 AM #2
Hi Bob,
Those measurements are about what I would expect, particularly the digital ones.
I've several cheap digital callipers and a 10 mm precision reference. At 10 mm all my instruments would show the same scatter as yours show.Best Regards:
Baron J.
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19th Sep 2018, 06:31 PM #3Banned
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Micrometers come with test bars, why don't you use them?
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19th Sep 2018, 06:58 PM #4Most Valued Member
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19th Sep 2018, 08:31 PM #5Intermediate Member
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Unless you have a traceable reference standard all the measurements you do are only comparitive .
By traceable I mean a reference having a NATA endorsed report attached to it.
Alfclp
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19th Sep 2018, 09:38 PM #6Senior Member
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20th Sep 2018, 10:12 AM #7Most Valued Member
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Correction - this was on ONE occasion, however it was very noticeable, hence I did the comparison.
I checked it against several other Mitutoyo and Moore and Wright calibration cylinders/blocks from my other caliper sets.
It was definitely out of spec (oversize) by a considerable margin - and it was an original/genuine vernier Mitutoyo micrometer, not some cheap clone.The worst that can happen is you will fail.
But at least you tried.
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20th Sep 2018, 10:29 AM #8Most Valued Member
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20th Sep 2018, 11:16 AM #9Most Valued Member
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