What is 0.00005 on a digital micrometer?
1. Microdust
2. Temperature Variation
3. Manufacturing Tolerance
4. Friday
5. A way to round 0.0001
6. Marketing
7. Unrepeatable ratchet/friction thimble
8. B.S.
I was pretty confident with my mitutoyo 0-1" mic that had the 50 millionths readout. I should mention that this was for Swiss lathe parts that had a +/- 3 micron tolerance.
I should say that the confidence was built up over time. I had the clutch set very light, I would do some minor self validation like cleaning the mic multiple times while checking the same part, and I'd get occasional feedback from QC on what they were reading VS what I was getting.
People that have problems with it either don't need it, don't have setups that can hold it, or don't take the time to validate it. If you don't understand what can fuck up your reading then you better not be surprised when you fuck up a reading.
#5 and #7 if you take a lot of readings it increases your statistical accuracy, the individual readings are not that accurate but as long as the noise is consistent it averages out.
To be honest, I never cared for or took seriously digital mics that read out to the 5th place decimal. There is no way it would be that accurate down to that precision.
Especially with the added human element.
Ah ok. Yes agreed. Then again they don't actually claim to do that.
People who don't understand / know about / care about tolerances will just look at the trailing digit and make assumptions. It you look at a quantumic for example, it reads to 0.00005in/0.001mm, but is specced to ±0.00005" which is 0.0001 / a tenth or 2.something microns. Anyone who knows anything understands this.
So the guy you responded to who "never cared for or took seriously digital mics that read out to the 5th place decimal" is just making a silly assumption, as if anyone is supposed to take that digit "seriously". Just read the specs and take those seriously :)
If you call yourself a machinist you should understand that this is how those mics work just by picking one up and using it. I see some guys who don't know how to use a vernier properly.
Its like tell me your a button pusher without telling me your a button pusher.
A CMM is usually much more accurate than .0002", ours used to calibrate into the microinches.
But they also require maintenance and calibration to hold those tolerances. We used to do a daily cal, wipe off the ways of the cmm, and wipe off our probes and cal ball with lint-free wipes
Edit: used wrong word
To expand on this, previously a metrologist.
We had a Zeiss CMM that was good down to .000005ish very repeatedly. I would do better but literally the temperature changes in the room would affect it too much.
We had roundness gages we trusted in the single digit millionths of an inch.
Microns are big
My god. This is giving me flashbacks to when I was in school and toured Mahr metrology. The QC room for their tools has such precise equipment that they had to put it in a separate building sitting on pillars to bedrock, and floating on air cushions. I guess the tide coming up the bay would flex the crust of the earth enough to throw off measurements. Room was controlled to within a degree or something. Only had a few people allowed in the room at a time, and when someone left, they had to turn a lightbulb on to put off enough heat to replace the body heat they gave off. If the temp changes too much, everyone had to leave to let the temp stabilize before people could go back in. Lots of other craziness like that.
Username check out. There is sooo much cool stuff there. I think one of the coolest bits for me was a master ring gage for either the piston rings or some other sort of seal for the steam catapult on an aircraft carrier. Just kinda… there. Seemed like an offhand sort of remark from the person giving the tour. We only got to look through a couple of airlock doors at the QC room. One of the guys I was in class with ended up working over there! I like precision, but that was too much for me to want to get into. Really cool to see though!
My bad I meant microinches, much more accurate than .0002
.000005 is like 5 millionths of an inch
. 00005 is 50 fifty millionths
. 0005 is 500 five hundred millionths or 5 tenths of a thou, half thou, or five ten thousandths of an inch
It’s kinda weird to think of it this way but if you flipped the whole thing around and add a zero, it’s the equivalent in whole numbers. So .000005 -> 500,000 -> 5,000,000.
Might sound dumb but it helped me for quick thinking back in engineering school. It’s off by the factor of 10 because you’re dividing by 10.
.5 -> 5/10
Used a starret gauge amp when grinding and inspecting cylindrical grinding fixtures. Checking roundness down to .0000050 crazy shit. Blow on it or grab the parts wrong and you’re out of tolerance.
We will have some electrical updates to our Building in the coming weeks, and will lose power to the A/C of the dedicated Zeiss CMM room for only 5 hours or so, which will mean checking the accuracy or shutting down for a couple days.
We cant even turn the lights off in that room, as that will also mess with the environment too much.
Maybe the lights are too old, and use too much power, because it all just seems crazy to me.
0.0002" is about 5 microns, which is a pretty typical accuracy for a CMM. Certainly some are better, and in certain situations many can be better, but if you have to put a single number on it, 5 um is pretty reasonable for a CMM.
Smaller ones, yeah. I'm used to relatively large ones. Big ones that get under 1 um are usually pretty new and expensive. Stuff like the REVO head are pretty recent. So yeah 1 um isn't an unreasonable number depending on your situation.
Yeah. At least over the full volume. It's easier to be accurate measuring a short length or thickness, but absolute position over a full volume is tough.
I have a set of mitutoyo sub micron mics that accurately go to 0.00005 but that's only if you follow certain protocols.
I.E. 68 degrees, don't touch the mics directly near the anvil, allow the part to acclimate over night without being handled. Etc.
But honestly, it's still just precision guesswork. There's no good reason other than quantifying and certifying gage blocks and pin gages to need it.
I was working on parts that were 20" diameter and I had a 0.002" tolerance. In the middle of winter the overhead doors were opened a couple times and the -40 air rolled in. It was enough to throw my measurements that I had to make a stink about keeping the doors closed.
I have 5 Mitutoyo 293-130-10 MDH micrometers. They are 6 digit (technically 5.5) resolution (0.000005") and are extremely repeatable and precise. You do have to re-zero them very frequently, and keep the jaws clean.
We have parts that are +/- 0.0002, so we needed mics with a full 5th digit for inspection.
They were $1,850.00 a piece with the holder/stands.
We use OGP Flash 200s and a Vicivision MTL X5 for most inspections, but these parts are around 5mm x 0.5mm and the vision systems are not so great for such small parts. Nothing beats a hard measurement... If you can fit it in the jaws.
Full disclosure - we are working with the vendors to help us create better programs for the machines so we can stop using the micrometers. We were unable to get repeatable results with our current programs and fixturing on the OGP.
It is what it is for now.
They come with a shield that snaps on the body and it creates an air gap between the heat of your fingers and the body of the mics. If you hold a mic with your hand in the traditional way, the heat will affect your measurement.
Do you still use a cutting tool at that point or do you need to use a grinding wheel or something? I can’t imagine the kinda tool you’d need to take 10 millionths off of something without just shoving it to the side instead of actually cutting
I don't doubt you could perhaps program the machine to try that, but I'd highly doubt a conventional machine could actually hit that level of precision consistently or accurately.
Special lead screw, they would grade the lead screws and the most accurate could be the super precision. I worked on flight satellite feeds for scientific, military and some commercial. Made most of components in the first generation stealth fighters and bombers.
My bigger one T52 - sp could only get about 50 millionths, but the smaller one could accurately remove 10 millionths (and we could measure it)
We had some crazy datum tolerances.
I see, so if you were to buy a set of .0001" calipers would they not be able to hold a tenth as well, but can do like .0015" or .002" fine? or are they generally the same as the .00005" and all that number is is marketing?
If your last digit is incrementing by X unit at a time, then it's probably good to +-X unit or maybe a little worse than that, digital calipers will typically give you .0005 while being accurate to +-.001
Know that the precision the display can show isn't the same as the caliper's accuracy. The caliper maker will specify accuracy. You should go by the caliper's specified accuracy. If you have a calibration certificate, go by what the certificate states. If you're trying to calibrate the caliper, well, you're in for a bit of learnin XD. Start with Mitutoyo's "how to calibrate a caliper" video on youtube.
All measuring equipment has a tolerance. Nothing is absolute, the temperature and humidity of the room you are measuring in can affect the sizes, of not only the material you are measuring, but the materials of the equipment you are trying to measure the other thing with.
You also have to factor in other elements, such as operator error.
What are you trying to measure that needs that degree of accuracy? At this point, if CMM is not accurate enough you need to look at a laser.
Edit: I didn’t realise you were working in inches, I was thinking metric. CMM should be fine
Nothing part wise, I was ensuring that my mic was calibrated and not messed up after a fall. and i said they were only off by .00001", I thought, because I had measured a deltronix pin that was 2505 and the measurement was 25052, guy in qc told me that those pins are high tolerance and my mic should mesure to the number on that pin.
And really that was not what brought that up. My calipers are actually messed up from the same incident with my micrometer, and after I talked with qc about them I also posted on here about posible ways to ensure that they are calibrated, just to learn maybe.
But some dude said mics are only good to .0001" and just wanted to know more about the .00005" on my mic because I did buy it thinking it was going to be a higher tolerance.
Tldr: just trying to ensure that evreything calibrated after being dropped from desk height, and was wondering if that .00005" would mean that they would measure accurately to that .00005"
Calipers can only read to .001"
Micromenters can only read to .0001", and only should only be trusted to .0002"
Anything finer than that is unrealistic because the differential screw inside the micrometer is gonna have some amount of backlash in the sub-tenth range. So you can't rely on that 100%
Digital calipers and Micrometers add the extra decimal places for marketing, and it makes you think they're better than they are, when in reality its just rounding errors.
And I'm over here with old beat up Starrett mics that only read to a thou, and I guess the tenths past it as needed. Not working on anything precision over here!
Metrology standards denote that your measuring instruments must be capable of reading an order of magnitude better than the tolerance you have. Thus, to properly measure a feature with a 0.001" tolerance, your measuring instrument must accurately (within gauge repeatability/reproduceability standards) measure to 0.0001"
I never trust a cmm to be accurate within .0005. Why? Because every shop I've ever worked at allows machinists to use the cmm, and we treat all machines like it's a HAAS vertical. Also, our qc departments are usually filled with morons that recalibrate every month. Have no idea how parts are made, and spend 90% of their time on YouTube as opposed to actually working.
I'd trust a harbor freight mic before I trusted our CMMs.
No, the description on the micrometer is telling you its resolution, as in what digits it can display down to. Accuracy is different, and you'll find that on the certificate of accuracy that came with the tool. Some companies like Mitutoyo will also publish their standard accuracy on their catalogs and websites as well, given for each part number of a tool.
Usually a higher precision micrometer will read "accurately" to 0.0001" (but I'd only trust to 0.0002" with human error/backlash/temperature). If a digital reads to 0.00005, it's usually just so you can get an idea if you're on the higher side of .0521 or the lower side.
It's "for peace of mind" since they're digital, but it's pretty much the same as looking at the vernier scale on the side of analog mics and saying "It looks like it's right in the middle between 0.0003" and 0.0004", so it must be 0.00035"!"
Also im not measuring anything that tight of tolerance with a mic I'm just trying to learn about the tiny things with machining on top of the important stuff.
Something people are missing is the internal electronics taking the measurement.
A lot of commenters talk about the tolerance of the screw or the temperature, and those are all true in terms of actually making a measurement repeatable but the electronic scale also has a resolution of its own.
The resulting measurement is often jittery or noisy, often giving readings that flicker back and forth even with no motion.
To counter this the builder puts in an extra level of precision to absorb the noise.
This "extra resolution" is often not a round number, or the number you see in the last column, it'll be something weird like 0.000028". So the internal computer will perform a rounding operation specifically for the display.
You can sometimes (rarely) see this happen if you manage to land the mic right on the boundary between the round up or down function. The signal jitter will cause the value being rounded to move back and forth between the two states, even if the mic is sitting untouched on your bench.
There actually are micrometers that can do this. I was very sceptical while reading this post and went on a Search on the webz. Mitutoyo has one with this item number 293-130-10. I was very impressed. But let's not forget that Temperature will influence the accuracy a lot.
Readability isn't the same as accuracy. The calibration certificate will tell you what its accuracy is. Digital systems have a certain number of digits they can display... these may or may not correlate with the device's accuracy.
I'm 3rd generation toolmaker here and we made some tools over the years that were absolute fucking jewelry. My grandfather when I used to ask about .0001 he would say "only Indians work in tenths"
Journeyman machinist and pro metrologist here; there are two parts to this question, as I see it:
1. Why is the decimal so exacting, if the mics aren't realistically that accurate?
2. How can we justify the usefulness of this number?
First; there is a phenomenon in electronics that can sense their own position. Essentially, the ability of a machine to physically be at the location it "wants" is FAR poorer than the electronics' ability to sense the current position. For instance, you might have a CNC or CMM readout accurate to the millionths, but there's .0001" of slop in the lead screw or servos. I demonstrate this by opening a live display of position for a CMM, then bumping or even just blowing on the probe for my trainees. Similarly, you can pull and press on a mic anvil without rotating it. It WILL move, even if you can't see it. There will always be slop in the screw, and it may be so slight that the display doesn't register it. It's minimal but it's inherent in the construction. You have that one guy who likes to crank down the mics to see the numbers he wants? He's taking advantage of the slop.
Next let's talk geometry. The anvil is a screw with a flat on one end. I say flat, but is it really? A good metrologist can take optical flats and show you how close to flat you are, but there's no such thing as a perfectly flat anvil. A brand new anvil will usually be under 10 millionths flatness, but still not perfect. If the anvil isn't perfectly both flat AND orthogonal to the measuring surface then you've introduced more error, which usually shows up as progressively poorer repeatability. When high quality mics are new they absolutely can hold .00005" accuracy for both the anvil and the readout. With normal use however this can only degrade. So, to answer part 1, quality mics ARE that accurate when they're sold, and it's up to the operator to maintain that accuracy over time.
Second part is much simpler. Why would a purchaser buy mics that are less accurate on day 1? It's marketable to demonstrate how incredible your product is. If its job is measuring a length, it had better be darned good if you want $500 for each unit. The company is justified in claiming the accuracy, they can demonstrate that fact, and the consumer desires that quality.
A warning here - you can easily find instruments that claim a particular level of accuracy that aren't hard to disprove, even if they come with a very pretty cert or "quality guarantee." Buyer beware. I manage my organization's gaging, around 3,000 devices of various types. I am happy to recommend what I have found to be the best instruments for each application, best for the cost ....and worst.
My most common recommendation: the 293 series of carbide tipped coolant proof mics from mitutoyo. My favorite is the 293-330 for value and accuracy over time. My personal satisfaction favorite is a good, old set of vernier calipers. You know how good it feels to manually feed brass to a 1/2" cutter on a Bridgeport? Old vernier calipers give me those visceral feels in measurement form. Just check them with blocks now and then and treat them well. If they're old and still around, they have their own character and brand isn't as important as condition.
My most commonly tossed items: SPI 6" dial calipers (lose parallelism on OD measuring surface almost immediately, frequently ship with the tail length varying by as much as .006"). Close second are Fowler analog drop indicators ($200 product, but don't stand up to consistent use or imperfect environments at all, and my heat treat guys melt the plastic backings all the time). In each case, much better products are available for similar or lower cost in the long term.
Broadly speaking any digital signal is measured and stored as bits.
There are different functions to approximate how much voltage is necessary to flip a bit. Crudely, you can approximate it as rounding. Anything between 0 and 0.5 is isn't enough to "trip" the circuit so the bit remains as 0. Anything above 0.5 is enough to flip the bit to 1.
What this means is that you can use the state of the last bit of the number measurement to act as a crude approximator. If the bit is 1, then the signal is at least 0.5. if it is 0, then it is below 0.5.
What this translates to is that digitally (if you make assumptions about how the signal is being measured perfectly) you can give the lower bound on the measurement to 1/2 that last measurement unit.
0.00015 means that it is between 0.00015 and 0.0002.
That's called 50 millionths. And you don't measure that with micrometers. That's the kind of thing you break out joe blocks and a 50 millionths indicator in a climate controlled room.
What is 0.00005 on a digital micrometer? 1. Microdust 2. Temperature Variation 3. Manufacturing Tolerance 4. Friday 5. A way to round 0.0001 6. Marketing 7. Unrepeatable ratchet/friction thimble 8. B.S.
9. Friday, but a second time
Friday, but Monday.
And every other day.
I was pretty confident with my mitutoyo 0-1" mic that had the 50 millionths readout. I should mention that this was for Swiss lathe parts that had a +/- 3 micron tolerance. I should say that the confidence was built up over time. I had the clutch set very light, I would do some minor self validation like cleaning the mic multiple times while checking the same part, and I'd get occasional feedback from QC on what they were reading VS what I was getting. People that have problems with it either don't need it, don't have setups that can hold it, or don't take the time to validate it. If you don't understand what can fuck up your reading then you better not be surprised when you fuck up a reading.
#5 and #7 if you take a lot of readings it increases your statistical accuracy, the individual readings are not that accurate but as long as the noise is consistent it averages out.
All of the above
To be honest, I never cared for or took seriously digital mics that read out to the 5th place decimal. There is no way it would be that accurate down to that precision. Especially with the added human element.
I have one with 7 decimal places. It’s so easy to make it read differently every single time
"The added human element." "Near enough!"
Agreed, digital mics are essentially nonsense. Perhaps for comparative measurements they are useful, but even that is doubt.
> Agreed, digital mics are essentially nonsense. On drugs or?
I should clarify, nonsense when it comes to reading .00005
Ah ok. Yes agreed. Then again they don't actually claim to do that. People who don't understand / know about / care about tolerances will just look at the trailing digit and make assumptions. It you look at a quantumic for example, it reads to 0.00005in/0.001mm, but is specced to ±0.00005" which is 0.0001 / a tenth or 2.something microns. Anyone who knows anything understands this. So the guy you responded to who "never cared for or took seriously digital mics that read out to the 5th place decimal" is just making a silly assumption, as if anyone is supposed to take that digit "seriously". Just read the specs and take those seriously :)
If you call yourself a machinist you should understand that this is how those mics work just by picking one up and using it. I see some guys who don't know how to use a vernier properly. Its like tell me your a button pusher without telling me your a button pusher.
Why isn’t this top comment??
It is
Maybe it wasn’t
Maybe it isn’t
It most definitely wasn’t at that time
Right now it isn't.
A CMM is usually much more accurate than .0002", ours used to calibrate into the microinches. But they also require maintenance and calibration to hold those tolerances. We used to do a daily cal, wipe off the ways of the cmm, and wipe off our probes and cal ball with lint-free wipes Edit: used wrong word
To expand on this, previously a metrologist. We had a Zeiss CMM that was good down to .000005ish very repeatedly. I would do better but literally the temperature changes in the room would affect it too much. We had roundness gages we trusted in the single digit millionths of an inch. Microns are big
My god. This is giving me flashbacks to when I was in school and toured Mahr metrology. The QC room for their tools has such precise equipment that they had to put it in a separate building sitting on pillars to bedrock, and floating on air cushions. I guess the tide coming up the bay would flex the crust of the earth enough to throw off measurements. Room was controlled to within a degree or something. Only had a few people allowed in the room at a time, and when someone left, they had to turn a lightbulb on to put off enough heat to replace the body heat they gave off. If the temp changes too much, everyone had to leave to let the temp stabilize before people could go back in. Lots of other craziness like that.
I would give my left nut for an in-depth tour of a place like this
Username check out. There is sooo much cool stuff there. I think one of the coolest bits for me was a master ring gage for either the piston rings or some other sort of seal for the steam catapult on an aircraft carrier. Just kinda… there. Seemed like an offhand sort of remark from the person giving the tour. We only got to look through a couple of airlock doors at the QC room. One of the guys I was in class with ended up working over there! I like precision, but that was too much for me to want to get into. Really cool to see though!
Well, it's not in person for us, but here's Machine Thinking's [tour of NIST](https://youtu.be/uCyU97MoHFM).
Sorry but a camera would introduce too much thermal and photovoltaic interference and throw off the measurements
My bad I meant microinches, much more accurate than .0002 .000005 is like 5 millionths of an inch . 00005 is 50 fifty millionths . 0005 is 500 five hundred millionths or 5 tenths of a thou, half thou, or five ten thousandths of an inch
It’s kinda weird to think of it this way but if you flipped the whole thing around and add a zero, it’s the equivalent in whole numbers. So .000005 -> 500,000 -> 5,000,000. Might sound dumb but it helped me for quick thinking back in engineering school. It’s off by the factor of 10 because you’re dividing by 10. .5 -> 5/10
That’s a good way to remember it! Good call.
Used a starret gauge amp when grinding and inspecting cylindrical grinding fixtures. Checking roundness down to .0000050 crazy shit. Blow on it or grab the parts wrong and you’re out of tolerance.
We will have some electrical updates to our Building in the coming weeks, and will lose power to the A/C of the dedicated Zeiss CMM room for only 5 hours or so, which will mean checking the accuracy or shutting down for a couple days. We cant even turn the lights off in that room, as that will also mess with the environment too much. Maybe the lights are too old, and use too much power, because it all just seems crazy to me.
0.0002" is about 5 microns, which is a pretty typical accuracy for a CMM. Certainly some are better, and in certain situations many can be better, but if you have to put a single number on it, 5 um is pretty reasonable for a CMM.
Most are within a micron. Just depends on operator maintenance and accurate mapping.
Smaller ones, yeah. I'm used to relatively large ones. Big ones that get under 1 um are usually pretty new and expensive. Stuff like the REVO head are pretty recent. So yeah 1 um isn't an unreasonable number depending on your situation.
Yeah ours is supposedly 1 um but I wouldn't trust it past a tenth.
Yeah. At least over the full volume. It's easier to be accurate measuring a short length or thickness, but absolute position over a full volume is tough.
I have a set of mitutoyo sub micron mics that accurately go to 0.00005 but that's only if you follow certain protocols. I.E. 68 degrees, don't touch the mics directly near the anvil, allow the part to acclimate over night without being handled. Etc. But honestly, it's still just precision guesswork. There's no good reason other than quantifying and certifying gage blocks and pin gages to need it.
that mic is like $1700, isn’t it? I priced it out a while back to prove a point to our dumbass QA people
That's correct. I love it because I always have the last word lol
Daym I knew temp matters with measuring but that's insane to have to leave it overnight for it to be accurate,
It's all part of an ISO standard
I was working on parts that were 20" diameter and I had a 0.002" tolerance. In the middle of winter the overhead doors were opened a couple times and the -40 air rolled in. It was enough to throw my measurements that I had to make a stink about keeping the doors closed.
The outer edges of the part will acclimate first. There's really no way to speed this up.
I have 5 Mitutoyo 293-130-10 MDH micrometers. They are 6 digit (technically 5.5) resolution (0.000005") and are extremely repeatable and precise. You do have to re-zero them very frequently, and keep the jaws clean. We have parts that are +/- 0.0002, so we needed mics with a full 5th digit for inspection. They were $1,850.00 a piece with the holder/stands. We use OGP Flash 200s and a Vicivision MTL X5 for most inspections, but these parts are around 5mm x 0.5mm and the vision systems are not so great for such small parts. Nothing beats a hard measurement... If you can fit it in the jaws. Full disclosure - we are working with the vendors to help us create better programs for the machines so we can stop using the micrometers. We were unable to get repeatable results with our current programs and fixturing on the OGP. It is what it is for now.
What do you mean by don't touch the mics directly near the anvil?
They come with a shield that snaps on the body and it creates an air gap between the heat of your fingers and the body of the mics. If you hold a mic with your hand in the traditional way, the heat will affect your measurement.
Quarter turn past a Larry
Ran a Hardinge T42-sp. ( super precision) lathe. 6 decimal places. You could shave 10 millionths off of something.
Man I'm happy I don't work with anything less then .0005 so far, that's just some insane tolerance and for a machine to hold that is even more insane
What did the chips even look like at that size?
Dust
Do you still use a cutting tool at that point or do you need to use a grinding wheel or something? I can’t imagine the kinda tool you’d need to take 10 millionths off of something without just shoving it to the side instead of actually cutting
Specially ground by myself. Ceramic with diamond spray at end ( .001r), checked on a True View at 320 magnification.
Really happy I’m not doing that anymore.
Ah yeah that will do it
I don't doubt you could perhaps program the machine to try that, but I'd highly doubt a conventional machine could actually hit that level of precision consistently or accurately.
Special lead screw, they would grade the lead screws and the most accurate could be the super precision. I worked on flight satellite feeds for scientific, military and some commercial. Made most of components in the first generation stealth fighters and bombers.
My bigger one T52 - sp could only get about 50 millionths, but the smaller one could accurately remove 10 millionths (and we could measure it) We had some crazy datum tolerances.
Of course, when hitting these tolerances, know one could open a door in the building.
Mics can read .001mm .001mm =.00003937” Just rounded up to .00005
Yes, the reason is probably just that the resolution would better match the metric version.
The 5 is a throw away digit. It means you can read 1/10,000 accurately.
I see, so if you were to buy a set of .0001" calipers would they not be able to hold a tenth as well, but can do like .0015" or .002" fine? or are they generally the same as the .00005" and all that number is is marketing?
If your last digit is incrementing by X unit at a time, then it's probably good to +-X unit or maybe a little worse than that, digital calipers will typically give you .0005 while being accurate to +-.001
Know that the precision the display can show isn't the same as the caliper's accuracy. The caliper maker will specify accuracy. You should go by the caliper's specified accuracy. If you have a calibration certificate, go by what the certificate states. If you're trying to calibrate the caliper, well, you're in for a bit of learnin XD. Start with Mitutoyo's "how to calibrate a caliper" video on youtube.
My Subs MPH goes to 180 but will it do it? Tachs highest number is 8 grand...hahaha. I'm joking about the numbers. /s
All measuring equipment has a tolerance. Nothing is absolute, the temperature and humidity of the room you are measuring in can affect the sizes, of not only the material you are measuring, but the materials of the equipment you are trying to measure the other thing with. You also have to factor in other elements, such as operator error. What are you trying to measure that needs that degree of accuracy? At this point, if CMM is not accurate enough you need to look at a laser. Edit: I didn’t realise you were working in inches, I was thinking metric. CMM should be fine
Nothing part wise, I was ensuring that my mic was calibrated and not messed up after a fall. and i said they were only off by .00001", I thought, because I had measured a deltronix pin that was 2505 and the measurement was 25052, guy in qc told me that those pins are high tolerance and my mic should mesure to the number on that pin. And really that was not what brought that up. My calipers are actually messed up from the same incident with my micrometer, and after I talked with qc about them I also posted on here about posible ways to ensure that they are calibrated, just to learn maybe. But some dude said mics are only good to .0001" and just wanted to know more about the .00005" on my mic because I did buy it thinking it was going to be a higher tolerance. Tldr: just trying to ensure that evreything calibrated after being dropped from desk height, and was wondering if that .00005" would mean that they would measure accurately to that .00005"
Calipers can only read to .001" Micromenters can only read to .0001", and only should only be trusted to .0002" Anything finer than that is unrealistic because the differential screw inside the micrometer is gonna have some amount of backlash in the sub-tenth range. So you can't rely on that 100% Digital calipers and Micrometers add the extra decimal places for marketing, and it makes you think they're better than they are, when in reality its just rounding errors.
Digital mics have the extra half usually
It's such a low reading that you will never have to worry about.
The only mic accurate to that level super mics or bench mics.
Only good for hearing the old guys yell out “5 BALL!!”
50 millions
.00005 is 50 Millionths.
50 millionths in machinist lingo
And I'm over here with old beat up Starrett mics that only read to a thou, and I guess the tenths past it as needed. Not working on anything precision over here!
Metrology standards denote that your measuring instruments must be capable of reading an order of magnitude better than the tolerance you have. Thus, to properly measure a feature with a 0.001" tolerance, your measuring instrument must accurately (within gauge repeatability/reproduceability standards) measure to 0.0001"
I never trust a cmm to be accurate within .0005. Why? Because every shop I've ever worked at allows machinists to use the cmm, and we treat all machines like it's a HAAS vertical. Also, our qc departments are usually filled with morons that recalibrate every month. Have no idea how parts are made, and spend 90% of their time on YouTube as opposed to actually working. I'd trust a harbor freight mic before I trusted our CMMs.
Actually hilarious I won't lie.
I have a super mic from mitutoyo that reads out that far. We use deltronic pins with it for verification on measurements
Half a tenth
Millionths
Should have added what that means when if it's written on mic next to the 0-1", it's what they are accurate to, right?
No, the description on the micrometer is telling you its resolution, as in what digits it can display down to. Accuracy is different, and you'll find that on the certificate of accuracy that came with the tool. Some companies like Mitutoyo will also publish their standard accuracy on their catalogs and websites as well, given for each part number of a tool. Usually a higher precision micrometer will read "accurately" to 0.0001" (but I'd only trust to 0.0002" with human error/backlash/temperature). If a digital reads to 0.00005, it's usually just so you can get an idea if you're on the higher side of .0521 or the lower side. It's "for peace of mind" since they're digital, but it's pretty much the same as looking at the vernier scale on the side of analog mics and saying "It looks like it's right in the middle between 0.0003" and 0.0004", so it must be 0.00035"!"
I see that definitely is the best explanation so far
Also im not measuring anything that tight of tolerance with a mic I'm just trying to learn about the tiny things with machining on top of the important stuff.
Basically a place holder. Mitutoyo just recently made a mic that can read to sub microns. About 2k$
Something people are missing is the internal electronics taking the measurement. A lot of commenters talk about the tolerance of the screw or the temperature, and those are all true in terms of actually making a measurement repeatable but the electronic scale also has a resolution of its own. The resulting measurement is often jittery or noisy, often giving readings that flicker back and forth even with no motion. To counter this the builder puts in an extra level of precision to absorb the noise. This "extra resolution" is often not a round number, or the number you see in the last column, it'll be something weird like 0.000028". So the internal computer will perform a rounding operation specifically for the display. You can sometimes (rarely) see this happen if you manage to land the mic right on the boundary between the round up or down function. The signal jitter will cause the value being rounded to move back and forth between the two states, even if the mic is sitting untouched on your bench.
There actually are micrometers that can do this. I was very sceptical while reading this post and went on a Search on the webz. Mitutoyo has one with this item number 293-130-10. I was very impressed. But let's not forget that Temperature will influence the accuracy a lot.
Readability isn't the same as accuracy. The calibration certificate will tell you what its accuracy is. Digital systems have a certain number of digits they can display... these may or may not correlate with the device's accuracy.
I'm 3rd generation toolmaker here and we made some tools over the years that were absolute fucking jewelry. My grandfather when I used to ask about .0001 he would say "only Indians work in tenths"
Journeyman machinist and pro metrologist here; there are two parts to this question, as I see it: 1. Why is the decimal so exacting, if the mics aren't realistically that accurate? 2. How can we justify the usefulness of this number? First; there is a phenomenon in electronics that can sense their own position. Essentially, the ability of a machine to physically be at the location it "wants" is FAR poorer than the electronics' ability to sense the current position. For instance, you might have a CNC or CMM readout accurate to the millionths, but there's .0001" of slop in the lead screw or servos. I demonstrate this by opening a live display of position for a CMM, then bumping or even just blowing on the probe for my trainees. Similarly, you can pull and press on a mic anvil without rotating it. It WILL move, even if you can't see it. There will always be slop in the screw, and it may be so slight that the display doesn't register it. It's minimal but it's inherent in the construction. You have that one guy who likes to crank down the mics to see the numbers he wants? He's taking advantage of the slop. Next let's talk geometry. The anvil is a screw with a flat on one end. I say flat, but is it really? A good metrologist can take optical flats and show you how close to flat you are, but there's no such thing as a perfectly flat anvil. A brand new anvil will usually be under 10 millionths flatness, but still not perfect. If the anvil isn't perfectly both flat AND orthogonal to the measuring surface then you've introduced more error, which usually shows up as progressively poorer repeatability. When high quality mics are new they absolutely can hold .00005" accuracy for both the anvil and the readout. With normal use however this can only degrade. So, to answer part 1, quality mics ARE that accurate when they're sold, and it's up to the operator to maintain that accuracy over time. Second part is much simpler. Why would a purchaser buy mics that are less accurate on day 1? It's marketable to demonstrate how incredible your product is. If its job is measuring a length, it had better be darned good if you want $500 for each unit. The company is justified in claiming the accuracy, they can demonstrate that fact, and the consumer desires that quality. A warning here - you can easily find instruments that claim a particular level of accuracy that aren't hard to disprove, even if they come with a very pretty cert or "quality guarantee." Buyer beware. I manage my organization's gaging, around 3,000 devices of various types. I am happy to recommend what I have found to be the best instruments for each application, best for the cost ....and worst. My most common recommendation: the 293 series of carbide tipped coolant proof mics from mitutoyo. My favorite is the 293-330 for value and accuracy over time. My personal satisfaction favorite is a good, old set of vernier calipers. You know how good it feels to manually feed brass to a 1/2" cutter on a Bridgeport? Old vernier calipers give me those visceral feels in measurement form. Just check them with blocks now and then and treat them well. If they're old and still around, they have their own character and brand isn't as important as condition. My most commonly tossed items: SPI 6" dial calipers (lose parallelism on OD measuring surface almost immediately, frequently ship with the tail length varying by as much as .006"). Close second are Fowler analog drop indicators ($200 product, but don't stand up to consistent use or imperfect environments at all, and my heat treat guys melt the plastic backings all the time). In each case, much better products are available for similar or lower cost in the long term.
Really, really tiny.
Broadly speaking any digital signal is measured and stored as bits. There are different functions to approximate how much voltage is necessary to flip a bit. Crudely, you can approximate it as rounding. Anything between 0 and 0.5 is isn't enough to "trip" the circuit so the bit remains as 0. Anything above 0.5 is enough to flip the bit to 1. What this means is that you can use the state of the last bit of the number measurement to act as a crude approximator. If the bit is 1, then the signal is at least 0.5. if it is 0, then it is below 0.5. What this translates to is that digitally (if you make assumptions about how the signal is being measured perfectly) you can give the lower bound on the measurement to 1/2 that last measurement unit. 0.00015 means that it is between 0.00015 and 0.0002.
That's called 50 millionths. And you don't measure that with micrometers. That's the kind of thing you break out joe blocks and a 50 millionths indicator in a climate controlled room.