Do you have to “zero” a new micrometer?

[TheOldHokie]

Tap (or if past zero, tighten) to move the slip barrel. It's right when closed, it zero's.

have no idea how you do that. You cant "close the jaws" on a traditional 1-2", 2-3", 3'4" etc micrometer. You have to put a standard between the jaws to establish the zero position. Running the screw in to the limit of travel is not zero. You can close the jaws on a 0-1" micrometer which is why they dont come with a standard.

Dan

 

[Workerbee]

Not really relevant to your micrometer, but I was looking to buy a mitutoyo digital caliper, so of course checked on ebay. You can buy them for about 1/4 of what an authorized distributor gets. Why? Because theyre fake chinese crap. Evay is rampant with counterfitted products. I doubt they care either.

 

[TheOldHokie]

[

Not really relevant to your micrometer, but I was looking to buy a mitutoyo digital caliper, so of course checked on ebay. You can buy them for about 1/4 of what an authorized distributor gets. Why? Because theyre fake chinese crap. Evay is rampant with counterfitted products. I doubt they care either.

As a man who has owned three genuine Mitutoyo 6" digital calipers all purchased from suthorized dealers save yourself the grief of skipped counts and spend a few bucks more for a Starrett.

Dan

 

[Gaspasser]

Dead balls on accurate? It's an industry term.

 

[Lil Foot]

[

As a man who has owned three genuine Mitutoyo 6" digital calipers all purchased from suthorized dealers save yourself the grief of skipped counts and spend a few bucks more for a Starrett.

Dan

Hey, I kinda like Mitutoyos.

 

[TheOldHokie]

Hey, I kinda like Mitutoyos.
View attachment 168844

I have a good collection of Mitutoyo manual micrometers and dial calipers/indicators. Happy with all of them. But I had 3 of those 6" digital calipers and all three started skipping counts shortly after purchase. They were not trustworthy to +/- .005. Makes me very wary of any digital Mit instrument. For the relatively small difference in price I will buy Starrett just for the peace of mind.

Dan

 

[hagrid]

No love for Brown & Sharpe?

 

[TheOldHokie]

No love for Brown & Sharpe?

I have no problem with luxury brands have a handfull of analog B&S instruments all purchased used.

Dan

 

[Lil Foot]

I have a good collection of Mitutoyo manual micrometers and dial calipers/indicators. Happy with all of them. But I had 3 of those 6" digital calipers and all three started skipping counts shortly after purchase. They were not trustworthy to +/- .005. Makes me very wary of any digital Mit instrument. For the relatively small difference in price I will buy Starrett just for the peace of mind.

Dan

Admittedly, never owned any 6" Mits.
I like all the good stuff, and worked with an old guy who worked for B&S for years, and when he retired, I ended up with a lot of B&S stuff from him.
I have had problems with ChiCom crap, even went so far as to drill .45 holes in some of it.

 

[Old Machinist]

I have never bought a micrometer or caliper that was off. I recently purchased a inexpensive digital caliper off Amazon to replace my cheaper HF caliper. I checked it through the range with all my micrometer standards and it was dead on with all of them.

 

[William1]

have no idea how you do that. You cant "close the jaws" on a traditional 1-2", 2-3", 3'4" etc micrometer. You have to put a standard between the jaws to establish the zero position. Running the screw in to the limit of travel is not zero. You can close the jaws on a 0-1" micrometer which is why they dont come with a standard.

Dan

All my mics are small 2" and under old Staretts.

 

[William1]

I have a Mitutoyo digital 6" caliper. Worked well for 30 years, then got funky, error and failed. I sent it in and they 'rebuilt' it at no charge about 5 years back. More than accurate enough for a guy like me that excels at making oval holes and unstraight lines.

 

[William1]

I knew a guy, excellent finish carpenter. Gave me a measurement, I cut it exactly. It was about 3/16" short. Seems his tape was damaged and as long as he measured and cut using it, he was fine.....
Relative... Relatives, makes all the difference.
I imagine using a standard one requirement is temperature. Though I'd suppose an optical measurement would be indifferent to temps.

 

[bird dogger]

Many years ago, I happened to be working alone in our instrument shop when a lineman with an attitude walked in and non politely said I should get off my a$$ and fix his 6 ft folding wooden ruler. He needed it in 30 minutes as they were leaving for some structure repairs and new crossarm installations. He handed me the broken ruler with a small handful of broken wooden pieces and then left muttering some obscenities and it had to be ready when he returned.

Super glue couldn’t account for the missing shards of wood in the broken section, so I did the next best thing. I opened up the nice brass hinges and removed one brass hinge and the broken wood section from the middle of the ruler. Back together again the fix was unnoticeable, unless you looked at the numbers.

The lineman came back and asked for his ruler. Told him its on the bench, ready to go. He opened it up and said “Damn, you can’t even see where you glued it back together!” I said “nope”, and he walked out.

Rumor has it that there’s a whole bunch of crossarms mounted with a bunch of extra holes drilled exactly 6” from the correct mounting holes. I would’ve loved to have heard the language between the ground crew and the one on the pole when they kept getting their measurements wrong!!

 

[Runs With Scissors]

Many thanks for all the replies guys.

The last time I had any calibration done to my mic was "way back in the day”, when I worked for Chrysler Pentastar Aviation, working on jets.

They required us to turn in our mics to the tool room, and they would send them out to be calibrated.

According to this pic, it has been “a while”

@Lil Foot and @Yooper might be onto something here.

I had just grabbed it off the frozen porch, and the only thing I did when I opened the box was to peel off the wax ends on the standard, and commenced to checking it.

I may have “wiped it off” on my shirt to clean it, but I would not "testify in court" to that….Can’t remember………..

It’s been in the shop for a few days now, so I’ll give it a good cleaning and recheck it.

 

[TheOldHokie]

I imagine using a standard one requirement is temperature. Though I'd suppose an optical measurement would be indifferent to temps.

You dont have to suppose and your supposition is wrong.

I had the good fortune to spend my last 25 years of employment at NIST's Gaithersburg. MD campus where all of these certifications are originated. While I did not work in physical metrology I got a chsnce to visit and view some very state of the art metrology labs and talk with some very knowledgeable people where I learned a lot. No brag, just fact.

Heres a link to the the latest edition of The Gauge Block Handbook.

https://www.nist.gov/system/files/documents/calibrations/mono180.pdf

Its published by the Dimensional Metrology Group that is responsiple for the physical artifacts and certifications at the root of all NIST dimensional calibrations and certifications. It will tell you more than you ever thought possible about accuracy of linear measurements and the certification process. Its not an easy read.

Since length dimensional standards are now based on the wavelength of light the physical artifacts (standards) used at NIST are themselves second generation standards and are optically re-calibrated on a periodic basis. Thats necessary to verify the standards have not degraded with use and ensure the integrity of the certification chain.

As you can see from the snippet below the accuracy of that optical recalibration is dependent on four physical factors where as the accuracy of the physical standards themselves are dependent on just one.

Dan

2.2.2 Nomenclature and Definitions

A gauge block is a length standard having flat and parallel opposing surfaces. The crosssectional shape is not very important, although the standard does give suggested dimensions for rectangular, square and circular cross-sections.

Gauge blocks have nominal lengths defined in either the metric system (millimeters) or in the English system (1 inch = 25.4 mm).

The length of the gauge block is defined at standard reference conditions: temperature = 20 ºC (68 ºF ) barometric pressure = 101,325 Pa (1 atmosphere) water vapor pressure = 1,333 Pa (10 mm of mercury) CO2 content of air = 0.03%.

Of these conditions only the temperature has a measurable effect on the physical length of the block. The other conditions are needed because the primary measurement of gauge block length is a comparison with the wavelength of light.

For standard light sources the frequency of the light is constant, but the wavelength is dependent on the temperature, pressure, humidity, and CO2 content of the air.

These effects are described in detail later.

 

[Old Machinist]

Maybe off topic but I bought this cheap caliper off Amazon and it was dead on with my 1", 2", and 3" standards after zeroing in the closed position. My old HF unit was always hard to keep batteries in so I sought out something better and so far this is that.

https://www.amazon.com/dp/B08Y8M54M9?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1

 

[TheOldHokie]

Maybe off topic but I bought this cheap caliper off Amazon and it was dead on with my 1", 2", and 3" standards after zeroing in the closed position. My old HF unit was always hard to keep batteries in so I sought out something better and so far this is that.

https://www.amazon.com/dp/B08Y8M54M9?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1

Not at all off topic and exactly what you would ecpect. Put it into use where its regularly exposed to a IP67 environment and test it again after 6 months. It will probably become problematic if not inoperative long before that.

The say you only get what you pay for and sometimes not even that.

Dan