Why would an electronic outside micrometer not return to zero?

[erikmannie]

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.

 

[Stonebriar]

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.

 

[Flyinfool]

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?

 

[pdentrem]

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

 

[erikmannie]

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.

 

[erikmannie]

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.

 

[erikmannie]

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”.

 

[erikmannie]

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.

 

[mikey]

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.

 

[Winegrower]

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.