# Why would an electronic outside micrometer not return to zero?



## erikmannie (Mar 8, 2020)

I have six Shars digital electronic outside micrometers that I bought new. They all behave the same: it seems that they cannot hold a zero.

The resolution is to .00005”, but I am never concerned about the hundred thousandths place, which in this case is always either a 0 or 5. I only want the micrometer to hold a zero in the .001 or .0001 position, and I wouldn’t even mind if there was up to .0005” variation. For the price I paid for these, I wouldn’t expect them to hold a zero with a .0001” variation.

Being as careful as I can be with regard to cleaning the anvils and always ratcheting the same number of clicks (two clicks), it will get me back to the same thousandths position about 50% of the time. 

With regard to tenths, it is just all over the place. You’re not using this micrometer to measure any tenths, which makes me wonder why it has the resolution that it does.

I had earlier posted a variation of this same question, and temperature was mentioned. The behavior that I mention in this post is in the same location (standing in one place) over a few minutes, so I don’t think temperature would be the reason for the inconsistency.

I think that the best that these micrometers would ever be able to do is get me to within a thou, and if anybody has any tips on how I could do that with these cheap micrometers, I would be interested to hear it.

I have about a dozen Starrett ratcheting analog (436 series) micrometers, and they have never exhibited this problem. They always return to zero as one would expect.

I think that the explanation for this inconsistency relates to the level of quality and workmanship of the tool, but I hope that I am missing something because I invested several hundred dollars in these.


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## Stonebriar (Mar 8, 2020)

That is a problem I have heard about Shars micrometers. I was looking at a Shars thread mic but word was that they were inconsistent on the readings.


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## Flyinfool (Mar 8, 2020)

When getting down to that small of numbers temp can make a difference. While you are holding the mike its temp is rising due to your body heat being absorbed. the electronics also generate some heat and temp change can alter the electrical characteristics. These 2 things combined could result in a variation over several minutes of holding them. 
Do some testing, does the error always go in the same direction?
After setting it down for a few hours does it go back to correct zero?


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## pdentrem (Mar 8, 2020)

We use Mitutoyo micrometers and pay good money for them. We make thin film solder forms that the customer insist on +/- 0.0002” most of the time. When we are making strip at 0.0005” the variations can cause near 50% waste. Fortunately we recycle all our metals.
The 5 digit ones will usually return to 0.00000 most of the time but the 0.000000 almost never. Temperature, magnetism, operator have been mentioned already. We also found gravity is a driving factor. We measure the strip on the rolling mill with the thimble vertical, but once the strip is off the mill, the next operator may hold the mic in multiple positions and we see variations around half the time.
The last digit is also a rounding digit on some mics.
Pierre


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## erikmannie (Mar 8, 2020)

Flyinfool said:


> When getting down to that small of numbers temp can make a difference. While you are holding the mike its temp is rising due to your body heat being absorbed. the electronics also generate some heat and temp change can alter the electrical characteristics. These 2 things combined could result in a variation over several minutes of holding them.
> Do some testing, does the error always go in the same direction?
> After setting it down for a few hours does it go back to correct zero?



The error goes in both directions, and setting it down for a few hours does not improve the situation. Long story short, the Shars micrometers will neither consistently hold a zero nor yield consistent measurements.

I hold all of my micrometers by the plastic heat shield if there is one.

I am doing a side by side comparison Shars versus Starrett, and if the temperature is a factor, then it doesn’t seem to have an effect on the Starrett micrometers. The Shars and Starrett definitely behave differently with regard to holding a zero and giving consistent measurements.

Obviously, I should have bought Starrett micrometers in the first place. The Shars tools look good and are affordable. The problems began for me when I put the equipment into service.


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## erikmannie (Mar 8, 2020)

pdentrem said:


> We use Mitutoyo micrometers and pay good money for them. We make thin film solder forms that the customer insist on +/- 0.0002” most of the time. When we are making strip at 0.0005” the variations can cause near 50% waste. Fortunately we recycle all our metals.
> The 5 digit ones will usually return to 0.00000 most of the time but the 0.000000 almost never. Temperature, magnetism, operator have been mentioned already. We also found gravity is a driving factor. We measure the strip on the rolling mill with the thimble vertical, but once the strip is off the mill, the next operator may hold the mic in multiple positions and we see variations around half the time.
> The last digit is also a rounding digit on some mics.
> Pierre



That is amazing that the Mitutoyo returns to the hundred thousandths position most of the time.

If anybody else has a quality brand of digital electronic outside micrometer, I would be curious as to whether or not it returns to zero.

I don’t think anybody is going to trust a measurement if the micrometer does not return to zero after the measurement is made.


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## erikmannie (Mar 8, 2020)

Obviously, I’m very happy with my Starrett ratcheting analog outside micrometers, and I am not yet a fan of the Shars electronic digital ones. 

Maybe I will never be able to get them to be consistent, and I can just relegate them to measuring the roughing work, thereby extending the life of the Starrett mikes.

As they are, these Shars digital electronic outside micrometers would be fine for work if the tolerance was .005”.


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## erikmannie (Mar 8, 2020)

I am not yet sold on digital electronic micrometers (or calipers, for that matter). I don’t have any problem with the analog type.

I wonder if people buy the digital electronic type is because they don’t want to mess with the spanner wrench.


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## mikey (Mar 8, 2020)

erikmannie said:


> I have six Shars digital electronic outside micrometers that I bought new. They all behave the same: it seems that they cannot hold a zero.
> 
> The resolution is to .00005”, but I am never concerned about the hundred thousandths place, which in this case is always either a 0 or 5. I only want the micrometer to hold a zero in the .001 or .0001 position, and I wouldn’t even mind if there was up to .0005” variation. For the price I paid for these, I wouldn’t expect them to hold a zero with a .0001” variation.



Erik, your post is really confusing. What do you mean by the underlined statement?

Perhaps more to the point, have you put the mic in a stand and used a gauge block to see if it reads what it should read? Even a Grade B block will be good enough to tell you if the mic is accurate or not. I cannot imagine that an entire set of mics would be this inaccurate.

If you want a good digital mic, buy a Mitutoyo mic. I have a Quantumike that is accurate to half a tenth and I have confirmed it with accurate gauge blocks. My Mitutoyo 500-752-20 calipers are dead on within its calibration range. For digital tools, Mitutoyo is probably the best out there.


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## Winegrower (Mar 8, 2020)

I think precision measurement is an area where you tend to get what you pay for.    I was excited to find a 50 millionths digital dial indicator for $35.   When I got it, it worked great.   Then the weather turned colder.   I discovered that if the shop temperature was below about 60 degrees F, the numbers just displayed randomly continuously.            I'm just waiting for spring, I guess.


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## erikmannie (Mar 8, 2020)

Winegrower said:


> I think precision measurement is an area where you tend to get what you pay for.    I was excited to find a 50 millionths digital dial indicator for $35.   When I got it, it worked great.   Then the weather turned colder.   I discovered that if the shop temperature was below about 60 degrees F, the numbers just displayed randomly continuously.            I'm just waiting for spring, I guess.



This may be a possible explanation, at least with regard to the tool behaving differently at temperatures much below 20°C. 99% of the measurements are taken in the shop, and it is probably about 50° to 60° F out there.


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## mikey (Mar 8, 2020)

erikmannie said:


> This may be a possible explanation. 99% of the measurements are taken in the shop, and it is probably about 50° to 60° out there.



Not really. I am asking you to clarify what you meant in the underlined statement in my post. I am confused.


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## erikmannie (Mar 8, 2020)

mikey said:


> Erik, your post is really confusing. What do you mean by the underlined statement?
> 
> Perhaps more to the point, have you put the mic in a stand and used a gauge block to see if it reads what it should read? Even a Grade B block will be good enough to tell you if the mic is accurate or not. I cannot imagine that an entire set of mics would be this inaccurate.
> 
> If you want a good digital mic, buy a Mitutoyo mic. I have a Quantumike that is accurate to half a tenth and I have confirmed it with accurate gauge blocks. My Mitutoyo 500-752-20 calipers are dead on within its calibration range. For digital tools, Mitutoyo is probably the best out there.



I used my Shars Grade B gage block set to investigate the situation, but as of yet I do not own a micrometer stand. The gage block set may have its own issues, but I want to take a more extensive look at that with metrology equipment that I trust before I comment further on that.

Another way of explaining the underlined statement is that when I bought the micrometers, I had hoped that it would be a micrometer where I could obtain consistent measurements down to tenths. Under these circumstances, I could get repeatable measurements to the nearest tenth. After realizing that this is an economy micrometer, I now hope that it will one day be able to give consistent measurements down to thousandths; under these circumstances, I would get consistent, repeatable measurements down to the nearest thousandths.


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## hanermo2 (Mar 8, 2020)

I tried 4 different cheap digital micrometers, and settled on a particular brand, shahe, after testing all 4.
I import micrometers.

The cheapest ones, 3 of, have problems in frame bend, and in repeatability.
Errors tend to be 2-3 microns, with no clear reason, aka they are sloppy  and poorly built.

The very very good shahe micrometers I import and sell cost only 35$ more.
The basic poor ones might cost 30$, 1", and the excellent one is 65$ (EU with 22% VAT).
The excellent mitutoy or federal or mahr about 150$.

The micrometers I sell and use repeat to about 1 micron and are accurate to about 1 micron, by blind testing with gage pins.
Equal to the best japanese mitutoyo/mahr/federal.


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## mikey (Mar 8, 2020)

hanermo2 said:


> The micrometers I sell and use repeat to about 1 micron and are accurate to about 1 micron, by blind testing with gage pins.
> Equal to the best japanese mitutoyo/mahr/federal.



For how long, I wonder?


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## erikmannie (Mar 8, 2020)

You machinists who bought digital electronic micrometers, may I ask why you chose that over analog? Maybe you save some time?


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## RJSakowski (Mar 8, 2020)

A modern micrometer should be able to provide consistant readings to within a couple of tenths.  It doesn't take much debris on the surface of the jaws to create inconsistent zeroing. In a metrology class, we were taught to clean the jaws by closing on a piece of paper and pulling  the paper out, wiping the jaws.

On my mikes with ratchets, I always ratchet more than two clicks, maybe a dozen or more.  The purpose of the ratchet is to limit the operator applied torque and properly set up, it should do that.  Using only two clicks should be fine for seating the jaw on the anvil but as soon as you put an object between the jaws, there is a possibility for canting the micrometer and getting a too high reading.  Rotating the ratchet as the micrometer gets settled in tends to provide more consistent readings for me.  

For a 1" piece of steel to grow in length by 1 mil due to thermal expansion, the temperature increase would have to be 86ºC or 155ºF. (Thermal expansion coefficient of steel is 10.8 - 12.5 microinches/inch/ºC).  Obviously, you don't want to make precision measurements on a workpiece that's smoking hot from heavy machining but for most work, slight variations due to temperature differences can be ignored.

Aluminum's CTE is about double that of steel and some plastics have 4 to 5 times that of steel so you should use a little more care when measuring those materials.


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## erikmannie (Mar 8, 2020)

So trying to make the change as large as possible within reason, if you measure 4.0000” OD on a steel round bar in a shop which is 0°C, what would that measure in an inspection lab at 20°C?

12.5 microinches X 20 = 250 microinches = .000250” per inch expansion going from 0° to 20°C, so the OD has increased by 4 X .00025” = .0010” in this example.

Here we have a machinist who is trying to nail 4.0000” OD with no tolerance specified. He does his work in an extremely cold shop, hopes that his work is good enough, and when the work gets the inspection lab it measures 4.0010”.


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## RJSakowski (Mar 8, 2020)

The biggest plus in my book for digital calipers and micrometers over their analog counterparts is the ability to set a zero at any point.  Second would be the ability to switch from mm to inches and back.  Another plus is ease of reading.  

That said, my go-to micrometer is a B&S 1" mechanical digital micrometer.  My 1" - 6" micrometer set is analog so anything over 1" get measured with an analog micrometer.  For calipers, I usually use digital calipers for the reasons stated.  I have a Starrett 24" vernier caliper that I use for measurements over 12" and a couple of German vernier calipers, the latter seldom used.


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## RJSakowski (Mar 8, 2020)

erikmannie said:


> So trying to make the change as large as possible within reason, if you measure 4.0000” OD on a steel round bar in a shop which is 0°C, what would that measure in an inspection lab at 20°C?
> 
> 12.5 microinches X 20 = 250 microinches = .000250” per inch, so the OD has increased by 4 X .00025” = .0010” in this example.


Correct.  If you were fitting a bearing, you would probably be concerned.    Metrology labs operate in temperature controlled environments and will let the objects equilibrate before measuring because they are usually dealing with accuracies in the microinch range. Calibration equipment and standards should be 4 - 10 x more accurate than the objects being calibrated.


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## higgite (Mar 8, 2020)

I may be wrong (I was once before ), but my guess would be that the inconsistency is in the ratchet, not necessarily in the measuring mechanism itself. Have you tried repeating measurements by feel without using the ratchet? You should be able to feel just the slightest resistance before the first ratchet click. Zero the mics at that point and repeat your measurements. Relying strictly on feel with both mics, do the Shars readings still consistently disagree with the Starrett readings?

Tom


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## mikey (Mar 8, 2020)

Just a few points of clarification. 

Mitutoyo says that errors in reading can be caused by excessive turns on the friction or ratcheting thimble. You want to use the least number of clicks before taking a reading; two is acceptable, more may lead to error.
If you want to evaluate a mic, put it in a stand or padded vise. This is not just to avoid thermal expansion. It is more to provide stability so you can position your gauge block properly and get an accurate reading. If you really need to know how accurate your tool is, do it right. Hand holding the mic and block is fraught with error.
 Temperatures do affect readings if you're working at extreme temps. If the shop is really cold and you're measuring a hot work piece with a cold mic then there will be errors; how much, I don't know. If you must know, both the work and the mic have to be at the same temp for several hours before you can reliably read it. If that doesn't work for you, move to Hawaii where temps are not as big of an issue.
The advantages for digital tools are as RJ said, and do not underestimate the impact of aging eyes on the ability to read an analog tool. I have some of the finest analog tools made but it's getting harder and harder to see them clearly. If you must go with digitals then invest in good tools. In this category, digital tools, Mitutoyo leads the field.


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## mksj (Mar 8, 2020)

I believe the issue is not so much accuracy as to repeatability under the "same" conditions. The "0" repeatability of 0.001" is quite poor for this level of precision which is usually specified. I prefer the Mitutoyo ratchet thimble, but my larger micrometers are Igaging Absolute's which has no ratchet, the plunger is spring loaded. Both are accurate and repeatable using gauge blocks to the last digit. The Shar's states their resolution 0.00005"/0.001mm Accuracy ±0.00015"/0.003mm, once zeroed I would expect it to repeat within the stated resolution. They have a 1 year warranty,if it is within this period ask to return it.


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## Liljoebrshooter (Mar 8, 2020)

I am wondering how you can compare a digital mic to an analog with a counter dial?
If you really want to get the answer about these mics, send one out to have it calibrated.  I bet it wouldn't cost as much as you think, maybe $50.  You can use it as a learning experience. 
Like I said before,   if these mic's bother you that much,  throw them in the trash and buy a brand new name brand one and be done with it. 

Joe


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## Liljoebrshooter (Mar 8, 2020)

Also like mksj stated above,  they may have 5 digit resolution but that doesn't mean they have 5 digit accuracy.
Joe


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## erikmannie (Mar 8, 2020)

Liljoebrshooter said:


> I am wondering how you can compare a digital mic to an analog with a counter dial?
> If you really want to get the answer about these mics, send one out to have it calibrated.  I bet it wouldn't cost as much as you think, maybe $50.  You can use it as a learning experience.
> Like I said before,   if these mic's bother you that much,  throw them in the trash and buy a brand new name brand one and be done with it.
> 
> Joe



After you said that, I bought 14 Starrett mikes. 

I wouldn’t throw the Shars in the trash because I can use them for roughing cuts.


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## erikmannie (Mar 8, 2020)

higgite said:


> I may be wrong (I was once before ), but my guess would be that the inconsistency is in the ratchet, not necessarily in the measuring mechanism itself. Have you tried repeating measurements by feel without using the ratchet? You should be able to feel just the slightest resistance before the first ratchet click. Zero the mics at that point and repeat your measurements. Relying strictly on feel with both mics, do the Shars readings still consistently disagree with the Starrett readings?
> 
> Tom



I will try this when I get home (in 7 weeks).


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## bill70j (Mar 8, 2020)

This discussion made me sit down and compare repeatability back to zero of two outside digital 0-1 micrometers.  A Harbor Freight $35 special and a Mitutoyo Digimatic 293-340-30.

The HFT brand returned to 0.0000 from 0.250 10 times in a row (two ratchet clicks)
The Mitutoyo brand returned to 0.000000 from 0.250 8 times and back to -0.00005 twice (two ratchet clicks)

Not sure what this test means, or doesn't mean - except that, although it was in no way a controlled test, it did nothing to shake my confidence that both measure well enough for the hobby work I do.

I also have an old mechanical (made in USA) Craftsman 0-1, 0.0001  and it also returns to zero repeatedly.


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## erikmannie (Mar 8, 2020)

I bought a PanaVise 391 for $42. I researched micrometer stands for several hours before I made my choice. I was going to joke and say that I bought a Shars micrometer stand.


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## francist (Mar 8, 2020)

Well all I can say is I’m glad you bought the Imperial vise and not the metric one. Can you imagine the grief trying to sort _that _out afterwards?


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## erikmannie (Mar 8, 2020)

francist said:


> Well all I can say is I’m glad you bought the Imperial vise and not the metric one. Can you imagine the grief trying to sort _that _out afterwards?



I have already started saving up for a metric micrometer holder. After that, I will one day buy a screw thread micrometer holder.


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## DavidR8 (Mar 8, 2020)

erikmannie said:


> After you said that, I bought 14 Starrett mikes.
> 
> I wouldn’t throw the Shars in the trash because I can use them for roughing cuts.



I’m still chewing on this statement:
“I bought 14 Starrett mikes”
Holy Moley!


Sent from my iPhone using Tapatalk


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## erikmannie (Mar 8, 2020)

DavidR8 said:


> I’m still chewing on this statement:
> “I bought 14 Starrett mikes”
> Holy Moley!
> 
> ...



I just wanted to have up to 7” and up to 175mm in both imperial and metric; that’s how we get the 14. Hopefully that was reasonable. They were discontinued models, and about half were used.

Of course, it’s the 0-1” that gets the lion‘s share of the work.


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## higgite (Mar 9, 2020)

erikmannie said:


> After you said that, I bought 14 Starrett mikes.
> 
> I wouldn’t throw the Shars in the trash because I can use them for roughing cuts.


Nah, if they turn out to be too inaccurate for finish work, they still make good C-clamps.  

Tom


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## MrWhoopee (Mar 14, 2020)

erikmannie said:


> I just wanted to have up to 7” and up to 175mm in both imperial and metric; that’s how we get the 14. Hopefully that was reasonable. They were discontinued models, and about half were used.



Geez, you sound like someone operating on a military budget.

My largest is 4 inch. I would like to have up to 6, but have no real justification. Metric mics? Is it really that hard to do the math? I'd be more likely to make a mistake reading them.


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## erikmannie (Mar 14, 2020)

I don’t have any problem converting English to metric, but I use a metric micrometer for metric work, inch pitch leadscrew notwithstanding. I don’t think that you would make a mistake reading a metric micrometer.

Regarding the budget, I spend very nearly zero discretionary money on anything other than tools, materials and schools. I haven’t owned a car in over 10 years, and I very rarely do anything else that isn’t free. I don’t know what I’m missing out on, but I’ll bet that it’s boring.


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## MrWhoopee (Mar 14, 2020)

erikmannie said:


> I haven’t owned a car in over 10 years, and I very rarely do anything else that isn’t free.







You are a better man than I! To be able to pull that off somewhere other than a major metropolitan center is truly impressive. I can understand how that would markedly increase your discretionary budget. Even without a car payment, cars constitute a large part of my monthly expenses.


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## mmcmdl (Mar 14, 2020)

erikmannie said:


> You machinists who bought digital electronic micrometers, may I ask why you chose that over analog? Maybe you save some time?



I have never and will never own anything electric . I was presented with a digital Mit caliper and it never came out of the packaging . It collects dust in the basement somewhere .


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## MrWhoopee (Mar 14, 2020)

mmcmdl said:


> I have never and will never own anything electric . I was presented with a digital Mit caliper and it never came out of the packaging . It collects dust in the basement somewhere .



The same for me, dial calipers and indicators, analog mics, vernier calipers & height gage. Oh, wait, I have an electronic calculator and a couple of DROs.


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## pdentrem (Mar 14, 2020)

At home I have analog tools ie hammer, screwdriver, saw and dial caliper and micrometer. At work we are issued digital Mitutoyo due to a few reasons. Mostly speed of reading the numbers as the material is moving pass the operator, too hard to read the barrel and having to do metric and imperial based upon customer requirements.

I also have two pocket watches from each of my grandfathers and I also own a solar powered wrist watch since 2002.
Pierre


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## erikmannie (Mar 14, 2020)

There is certainly nothing wrong with analog micrometers.


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## Boswell (Mar 14, 2020)

I have a Mitutoyo digital micrometer but hardly ever use it. My goto are the Mitutoyo Mechanical Digital. Never have to worry about batteries. I also have several of the Mitutoyo Digital Calipers that are solar powered so still no batteries to worry about and a few other mechanical mics of various sizes. Only the Calipers were bought new.


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## higgite (Mar 14, 2020)

I’ve never worried about batteries in a micrometer or calipers. I just change them when the go dead. 

Tom


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