It used to be that calipers were not a common item to have in an electronics lab. However, smaller parts, the widespread use of 3D printers and machining tools, and — frankly — cheap imported calipers have made them as commonplace as an ordinary ruler in most shops. But are you using yours correctly? [James Gatlin] wasn’t and he wants to show you what he learned about using them correctly.
The video that you can see below covers digital and vernier calipers. You might think digital calipers are more accurate, in practice, they are surprisingly accurate, although the digital units are easier to read.
Regardless of how you read them, there are four main methods of using the device. The big jaws measure the outside of things, and the tips on the other side can measure inner spaces. The video shows how to line up for the best accuracy.
The depth and step measurements are also common features and require care to position correctly, depending on what you are measuring. The step measurement is one we always forget about.
We didn’t realize that when you see CE on the back of your calipers, it might mean “conformité européenne” to reflect standards compliance, or China Export which means… well, probably nothing other than it came from China. How do you tell the difference? The video shows you.
If you have digital calipers, why not hack them? There’s more than one tweak you can make to them.
The “China Export” thing is a myth.
https://en.m.wikipedia.org/wiki/CE_marking#Misuse
Meh.
I’m also quite sure there is a town somewhere in China especially for all those “Made in Germany” stamps.
The amount of ways they manage to misspell “Mitutoyo” is also both hilarious and sad. While it’s still possible to buy something with “Mitutoyo” stamped on it (without spelling errors) and you can even buy it for prices high enough that it could be the real thing, you would be mad if you tried. Chinese law is (purposefully) very shaky on brandnames, which is very understandable if you realize they had none of their own for a long time and had therefore nothing to loose, while they had much to gain by playing the ignorant fool.
In the USA it used to be the opposite. They had strong brand names and still have (overzealous?) patriotism. And this has escalated to the point that it is forbidden to import yellow multimeters.
https://www.sparkfun.com/news/1430
It’s the difference between the west side and the east side of this round ball of mud.
https://xkcd.com/503/
The Chinese government gives tax subsidies for export-only companies as well, so the crappy fake-brand products don’t end up on the domestic market to compete with their own brands.
Y’might want to take a look at your local tax laws around export, most countries subsidise export companies via tax incentives.
Yar! Totally comparable in breadth, structure and function to Chinese State Owned Enterprise.
China has plenty of brand names. But there are certain requirements:
– They must be 6 letters long
– They must be all capitals
– They may or may not be pronounceable
(or so I have learned from Amazon)
like IKEA?
Huh?
Did the CCP buy Sweden?
Sigh… It’s a joke.
Being a vendor on Amazon requires registering a company, and the internal Amazon form used to require the name be 6 characters long.
That is why you see all those company names that are 6 random capital letters. Because they actually ARE just 6 random letters spit out by a character generator into the form until it lands on one that hasn’t been used yet.
It also makes it super easy to just generate a new name and register a new company if your review bots can’t keep your seller reputation in the positive…
Thanks [Ian]!
It whooshed me.
Just because there’s CE stampped on something does not mean they follow the rules of the actual CE marking, so might aswell be called “China export”. It’s just a another name for likely fraudulent use of the CE mark, which EC did address in that wiki page, but still managed to miss the point. Myth busted? Not really, since i do not think anyone was suggesting there was an actual, official China export-marking.
After out national electric safety centre (or what ever you call it) stopped prechecking the electric devices before allowing them on the market, they still do random testing and everytime they find hazardous devices. I bet each and every faulty device has a CE marking on it.
Besides, the CE-marking is on everything, it doesn’t mean jack shit to me. I do not know the rules of it and as said most likely a lot of the products have not been tested for compliance by the manufacturer anyways.
I think CE = China Export joke/meme came about because a lot of cheap China product makers just copy/paste regulatory certs. There’s no guarantee they’ve had any of the required testing unless it has the certification ID to lookup on the regulatory agency.
I recall the box of Chinese power strips we acquired in the 1990s, the Hot and Neutral were swapped on all the sockets.
The CE on the calipers does not mean China Export. It is just a fraudulent conformance stamp, intended not to be a technical violation of conformance certification.
Attractive myth? yup.
Long since debunked. Yup.
Even the Wikipedia page on the CE mark has a section devoted to this, and has for years.
The video is otherwise pretty good as an introduction. Just remember at all times: NO caliper is very good. Many are good enough. Abbe’s principle describes the primary geometric issues, but, additionally, only one of the three, four, or five common types of measurement can actually be in calibration, and the internal measure jaws usually need additional correction for knifeedge offset over the smaller (<25mm or do) sizes. Digital types allow for user compensation of offset, so can usually meet spec on regions of the (physical) scale that are in calibration for any but the inside jaws without further compensation.
My “best” digital caliper has a graduated resolution of 0.01mm (the 0.005mm caliper from the same prominent manufacturer has exactly the same precision and accuracy spec… the extra half digit is a distraction and meaningless). It is PRECISE to 0.03mm (the nature of the scale and measurement thereof) and ACCURATE to 0.05mm, though only for measures <100mm, and only for the calibrated outside measurement jaw faces at the point 1mm from the beam end of the ground surface, measuring a cylindrical part, at 20C. (The calibration is done using a steel reference, so on other materials, the tool will likely not meet standard, even with temperature correction)
Beyond 100mm, the accuracy drops, and there are several steps as the measure gets larger.
I do have a 1000mm caliper (vernier) with the same general specs, but it is calibrated at 800mm (last time), so from 700 to 900mm, it meets the above. If I need it in a different region, the vernier scale can be adjusted if needed at the time of calibration, though I think it will probably make calibration anywhere over the range as it is. I just haven’t had the need.
It is a rabbit hole…. A deep one. (Care to guess what a significant part of my professional life has involved?)
“It is a rabbit hole…. A deep one. (Care to guess what a significant part of my professional life has involved?)”
Measuring the inside diameter of rabbit holes?
B^)
Among other things. Mostly making sure that the outside diameter of the rabbit hole seal matches the inside diameter of the rabbit hole, lest the rabbit be flooded out somewhere in the middle of the north Atlantic during a hurricane.
The tolerance on the fit is 50microns for the 800mm rabbit holes…. No end of fun.
“Come out of that ho’ you kwazy wabbit!”
-Elmer Fudd
Good info for those lucky 10,000. https://xkcd.com/1053/
But my calipers have a dial, you insensitive clod!
You can get a set of precision length standards on eBay for thin money, and use these to confirm that your digital caliper is accurate.
A real digital caliper will turn off when you press the button, so the battery will last several years in typical usage. A cheap Chinese caliper will turn off the display, but not the caliper, when the button is pressed. These will drain the battery in 3 months or so, leading to always requiring a new battery when you need to use your caliper. Ugh!
Don’t use the thread/hole information on the back of the caliper, it’s a little complicated and it’s not as useful. Instead, look up a chart of “tap hole” and “clearance hole” for whichever screw/bolt you’re using and use the chart recommendation.
A standard drill set includes about 200 drills from 0 to 1/2 inch, so a full set has a drill about every 2 thou or so. There are three measurement systems: the fractions (5/32, 7/64, and so on), AWG (american wire gauge), and the lettered set, making about 200 drills in total.
If you use the actual clearance recommendation for tapping or clearance, it works out much much better than going with the closest fractional value. For example, for a 1/4 inch bolt you should use an F or H bit and not a 1/4 bit as you might expect.
My hobbyist work jumped an order of magnitude better once I started using the correct drills for the holes I needed. (Also, you can sometimes use the drill shanks to measure hole sizes, in cases where the caliper won’t work.)
Harbor Freight has a 115 cobalt drill set that has all three size types and works very well for clearance and tap holes.
https://www.reddit.com/r/harborfreight/comments/12gph06/is_the_115_piece_cobalt_bit_set_decent/
Here’s a chart of tap and clearance holes to use:
https://littlemachineshop.com/reference/tapdrill.php?srsltid=AfmBOop5p6EXLr2Nx_xOCnlqNy_fiWLKkxVTaVCIIBCSyWCus9XSc4Wv
Don’t get a caliper from Harbor Freight, ever. Go to the store, take one of the 6″ calipers out of the box, and run it back and forth with your finger. If it feels gritty like there’s sand in the mechanism, don’t buy it. Also, the Harbor Freight versions are the cheap Chinese ones that will eat a battery in a couple of months.
…and you’ll have to zero a Harbor Freight caliper before every measurement.
@PWalsh said: “A cheap Chinese caliper will turn off the display, but not the caliper, when the button is pressed. These will drain the battery in 3 months or so, leading to always requiring a new battery when you need to use your caliper. Ugh!”
Yep, I have a cheap Chinese digital caliper that does exactly that. So I replaced it with an even cheaper Chinese dial caliper – no battery at all ;-)
My 6″ Horror Fraught Pittsburgh brand digital caliper just turned on, it probably has been a month or two since I used it last. I bought it several years ago, and haven’t replaced the battery.
But, I don’t see a problem re-zeroing it every time, I mean, why not, if it is not zero, (and this one was when I powered it up) it only takes a second or two.
Good to see a guide on the verniers. I didn’t think anybody really bothered to learn those anymore. One of the last surviving cousins of the slide rule
Not a cousin to the slide rule, they have nothing in common as tools, but they are analog tools that are making wonders to our brain if used properly and often. I’m still carrying one 4 inch slide rule with me, even if I didn’t lived the times when it was common practice to do it so. I’m still searching for a metric micrometer with a vernier scale, not found one yet.
What nobody tells about vernier scales is that ticks are not spaced 1 mm but 0.09 mm (whe the main scale smallest indication is 1 mm), and when the measured size fraction is 0.1 mm (ie 20.1 mm), then the vernier scale tick at “1 mm” having 0.9 mm distance from the “0 mm” tick adds to that fraction, gets 1 mm and the ticks from the main scale and the vernier scale’s 1mm indication align. If the fraction of a mm from the measure its 0.3 mm, the distance between 0v (vernier) and 3v is 2.7 mm, adding that to 0.3 gets 3mm and the main and vernier scales ticks align at 3v.
I can see the ad right now on YouTube:
AMAZING! The FANTASTIC SHOCKING secret that machinists don’t want you to know! All these years you’ve been doing it WRONG!! “What nobody tells about vernier scales is…”
So…which buzzwords did I forget? :-D
I never watch Youtube videos that don’t feature some bearded guy with his mouth hanging open and a look of shock or anger on his face, and a backwards trucker cap on his head. I have found that those are the only ones worth watching.
You forgot to mention that it comes with a FREE CHICKEN (perhaps made of rubber) and a FREE PIRATE EYE PATCH so you can read easier the scale.
In my long roaming on the net didn’t found explained why the vernier scale works and I thought to let others know about it here (after I managed to find it on my own).
Well, wikipedia explains how the vernier scale functions on the vernier scale page directly under the header “Functioning”. So uhh, maybe check there first.
Look up the Caliputer, which is both a caliper and a slide rule.
$300 on eBay!
Wow!
https://www.ebay.com/itm/266865130683
I’ll calculate with what I’ve got, for that price, but it’s still smart – two things both made to slide with precision, and you may well want the area of a hole you’ve just measured the inner diameter of. Beats the price of those Curta’s.
A guy Chris Staecker shows these and similar gadgets.
https://www.youtube.com/watch?v=gZspI2ACUqM
{spaceminions}
Oh great, another rabbit hole to slide down…
Seriously, thanks for the link!
B^)
:D
Oh, not sure if he’s got a video on it, but a more affordable bit of extinct tech is these pocketwatch-like KL-1 circular slide rules that are floating around. They have their own somewhat interesting properties by being circular (so you wrap around at the ends) and from the way they’re made (two knobs, one face rotates one knob and both needles are on the other knob). There’s more than one way to perform the same operations, so you can work out the sequence of actions that produce the desired result in the least actions / best precision / least confusion and they may all be different sequences.
I’m a relative newcomer but I will always choose verniers because they are always ready to go when I pick them up – and surprisingly good genuine Mitutoyos can be had for not very much money.
I know “good” digital callipers don’t run their battery down as fast as the cheap ones but you still have to press a button to switch them on and check they’re zeroed, verniers are “always on”.
My $40 iGuaging caliper doesn’t seem to care if I switch it off or not, so I don’t bother switching it off, and the battery lasts more than a year. I don’t need to zero it before every measurement.
I’m surprised he didn’t say anything about dial calipers. I don’t trust the digital ones, since the first one I saw belonged to a QC man at the small company I was working for and he said something was out of spec and I could see that his digital caliper was visibly off, and even visually what it said was 1.000″ really looked more like 1.2″, so we measured, and yep, the digital one was way, way off.
I am currently looking at various Mitutoyo digital calipers models.
Is the thumbwheel really useful?
What (dis)advantages between standard and rod shaped depth gauge?
Data port could be useful, but proprietary cable seems quite expensive!
Personally I dislike the thumbwheel. I have cut it off of some of my callipers. (Shahe with dial) for several reasons.
1. So all my callipers have the same feel. (Closing force influences accuracy).
2. The thumbwheel does not add anything useful. It doubles the measuring pressure, but a high measuring pressure is not useful at all.
3. The thumbwheel makes it more difficult to open the callipers (it only moves half distance). And also, the wheel rotates your thumb off of it when you want to open it further. You have to move your thumb away from the thumbwheel and to another position if you want to open the callipers, which is annoying.
The rod for the depth may be handy if you want to measure small holes in which the flat bar does not fit. On the other hand, the flat bar has a notch and this is useful if you measure into holes which have a small radius at the bottom. the notch (when oriented correctly) ensures you do not measure the bottom radius but the real bottom of the hole. I prefer the flat bar, it’s more universal.
Data cable for Mitutoyo is ridiculously expensive. My Mitutoyo is 500-181-30 It probably is the cheapest model they have. I bought it new for EUR100, but buying it for that price now would be difficult. And I’m sure it’s a real one. I have it now for 7+ years and it’s still on it’s first battery. The empty battery indicator is on for about a year now but it still works. This model does not have a thumbwheel and it also does not have a dataport at all. The same version with data port (Without cable) is already around EUR 30 more expensive if you can find both models in the same shop. I’d say, if you want data, there are several projects on Hackaday to add the cable by DIY methods. Some use Bluetooth or Wifi (ESP32). The data format is simple, I believe it just spits out bcd digits in a serial fashion.
One thing I find absolutely essential is the “Absolute” part of this callipers. You set it once to 0, and after that, when you turn it on it shows the correct distance instantly. You don’t have to 1). Clean the jaws. 2). Close the jaws 3). Set it to 0. 4). Measure. You can even first measure something, and then turn it on for only a second to read the display.
Also, the Mitutoyo’s don’t turn of automatically. The callipers that do turn off automatically do so after a few minutes, which I find very annoying. (Especially when they are not the “absolute” kind.) But as a result, when you forget to turn it off and put it in a drawer, then it will drain it’s battery and it may be empty after 2 years instead of 7. Ideally, the callipers would turn itself off after a few hours or a day without measurements, but those probably don’t exist. But overall battery life is long enough that it does not matter much.
I am looking into buying a second digital callipers, because I have two locations where I want to use them. My second pair is maybe going to be a Chinese one, but it has to be an “absolute” version. They do exist, there are (apparently) reasonably decent chinese callipers for around EUR50 but the cheap ones are garbage. Every time I open or close my Mitutoyo I am amazed at how smooth it operates. It’s just a joy to use. Maybe just that is enough for my 2nd callipers to buy Mitutoyo again…
I have them with and without. It’s not getting in the way for me but when I need it, it’s amazing. Most of the times I get the one I have with a thumbwheel. Especially for depth marking it’s great. I only use the depth guage on normal calipers so I can’t answer that question. I have several calipers with USB ports on them, and I have yet to try it. I have no purpose for it. It might be great if you have a factory and have to constantly measure things based on software. Like when you have an employee that has to measure to verify measurement 1 is 39.32mm and measurement 2 is 43.51mm, or something like that. You can then verify it using software and repeat those actions easily. But for personal use, I don’t see a real use case.
having worked in a factory for over a decade now, I can tell you 2 things
The operators would destroy a set of calipers in about an hour (being nice), and they can’t be arsed to pay attention to red and green lights.. you are never going to get them to accurately measure anything.
I bet they could figure out a way to smoke meth off the glass of a quality caliper.
They will burn their fingers and file a workers comp claim though.
But he doesn’t demo the upper scale.
I have used calipers as a hobbyist for my entire life, but only last year, doing a woodworking course, I learnt the step function, and it’s so useful to know! I think not even all caliper makers know of this function, as 2 of the four calipers I have do not support it (the top end of the fixed and moving part are not the same height).
I have since updated https://en.wikipedia.org/wiki/Calipers with imagery.
Interesting. Always good to understand more about our tools.
I’m not doing tight tolerance anything in my hobby work, so the $30 store-branded digital caliper I have is just fine for me. I check the jaws, and zero it before measuring. Also I take the battery out when I put it away.
“You might think digital calipers are more accurate, in practice, they are surprisingly accurate, although the digital units are easier to read.”
I think you may have accidentally a word here. I’m guessing either a clause got deleted, or “they” refers to vernier calipers.
Am I using my calipers wrong if I use the pointy end to scratch the middle of my back?
Try not to damage your sternum.
A caliper (or calliper in Britain) is a measuring instrument. The three major types of calipers are: The digital caliper (uses a battery). The dial caliper (no battery needed). And the vernier caliper (also no battery needed). You can see all three caliper types at various price points on this page:
https://www.mcmaster.com/products/calipers/calipers-1~/
This page shows you how to read a vernier caliper:
https://www.mcmaster.com/products/calipers/calipers-1~/economy-vernier-calipers-10/
The vernier caliper is the simplest (often cheapest) caliper version, but is harder to use properly. A fairly good quality vernier caliper when used correctly should be on par with a decent digital caliper in terms of accuracy. More on calipers:
https://en.wikipedia.org/wiki/Calipers
Micrometers are not calipers. Vernier micrometers are similar to vernier calipers, but can be harder to read properly. More on micrometers:
https://en.wikipedia.org/wiki/Micrometer_(device)
To measure the accuracy of a caliper or micrometer, you need a standard. The most common measurement standard is a gauge block, or a set of gauge blocks. Guage block sets can be fairly cheap (See Amazon and Ebay), or fairly to very expensive. See this page from a fairly reputable vendor for examples of decent gauge block sets:
https://www.mcmaster.com/products/gauge-block-sets/
Gauge blocks require special use and care. Read more here:
https://en.wikipedia.org/wiki/Gauge_block
When using gauge blocks to aid in accurate measurements it is important to consider the concepts of “wringing” and the use of “optical flats”. For more on these subjects, see here:
https://en.wikipedia.org/wiki/Gauge_block#Wringing
Important, Cold Welding: Never store your measuring instruments or tools with metallic surfaces in direct contact long term. Metal surfaces in direct contact may undergo the process of “cold welding”. Read more on cold welding here:
https://en.wikipedia.org/wiki/Cold_welding
For example, I never store precision metal gauge blocks in contact with each other, plus I never allow a gauge block surface to remain in contact long term after wringing. Also, I always store my calipers and micrometers with a clean slip of paper soaked in a light machine oil (e.g. 3-IN-ONE oil), or better yet a slip of parchment soaked in CLP fluid (Cleaner, Lubricant and Protectant) between the measurement surfaces. Here is a good quality CLP example:
Lucas Oil Extreme Duty CLP Aerosol
https://www.amazon.com/Lucas-Oil-10916-Extreme-Aerosol/dp/B01D06TNAI/
That’s all I have for now on simple precision mechanical measurements. However the subject is quite deep – good luck.
a nice post explaining how Vernier scale works: https://circuit4us.medium.com/how-vernier-scale-works-db3f0dfca910