Author Topic: Digital calipers — what to buy?  (Read 6213 times)

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Offline sn4k3

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Re: Digital calipers — what to buy?
« Reply #25 on: July 17, 2018, 09:24:17 pm »
I own some cheap digital calipers from china, and they are bad. Not much because resolution but more because it keep lossing power and if you go far it will display a crazy value at random, so they are trash.
What i find good and so far it has been excelent is this: https://www.aliexpress.com/item/Waterproof-IP54-Electronische-Digitale-Messschieber-Measuring-tool-0-01mm-5001-150-Free-Shipping/1284242843.html

The battery size are better than the cheap ones, better resolution, no crazy jumps and you can log data with a USB cable to the PC. Since i have this i have 0 problems and very accurate values.
Worth the money
(Battery not included)

To larger sizes see: https://www.aliexpress.com/item/free-shipping-SHAHE-stainless-steel-0-150-mm-digital-caliper/32645456925.html
« Last Edit: July 17, 2018, 09:27:39 pm by sn4k3 »
 
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Offline G0HZU

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Re: Digital calipers — what to buy?
« Reply #26 on: July 17, 2018, 10:41:21 pm »
For many years I've been using these basic 150mm digital calipers and they are fairly cheap at about £36 from Farnell:

http://uk.farnell.com/linear-tools/49-923-150/digital-caliper-150mm-6/dp/1375863

They are a bit heavy on batteries (SR44) but I find them to be reliable and easily good enough for my needs. I've also got a set of genuine Mitutoyo 532 (fine adj) 150mm calipers. However, I only use these when I'm out of batteries for the digital calipers.

Obviously, these £36 digital calipers can't compete with a decent/expensive set from Mitutoyo but they seem to be reliable and I don't see any skipping/slipping effects with them. I think the accuracy spec is +/-0.02mm below 100mm and this is reasonable but not spectacular.
 

Offline Dubbie

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Re: Digital calipers — what to buy?
« Reply #27 on: July 17, 2018, 10:56:43 pm »
I've got mostly Mitutoyo gear in my shop. Micrometers, Calipers, Boregages, Height gages, Dial Indicators,  etc.

However I do have a couple of sets of measuremaX calipers that seem to perform as well as my Mitutoyo ones. They are about 1/2 price compared to the Mitutoyos
https://www.measumax.com/31-180

I have had some no-name Chinese ones in the past which have been rubbish. I think the lesson is, you get what you pay for.


 

Offline mmagin

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Re: Digital calipers — what to buy?
« Reply #28 on: July 17, 2018, 11:47:56 pm »
I bought one of the usual 6" Mitutoyos used on eBay a couple years back (very scuffed up case, but the instrument was just fine) and it's so much nicer than all the cheap calipers.  Also, the battery life is amazing.
 

Offline vltr

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Re: Digital calipers — what to buy?
« Reply #29 on: July 18, 2018, 01:04:57 am »

So it’s time for something proper. The local tool distributors carry a number of brands, and the ones I’ve been looking at are Mitutoyo (duh), Sylvac (Swiss) And Mahr (German). In fact one distributor has a sale right now covering a few models from each. (US brands are less likely to be available here.)

So what do I need to look for?
Since it seems you are most interested in feel and general quality I would recommend Japanese made mitutoyos.(Yes it does make a difference.  I have a pair of 1cm dial indicators one made in japan the other in us.  Same design same part number and the smoothness of movement, solidness, and general build quality are all much higher on the japanese made one).  I also have a brazilian made mitutoyo dial caliper I use every day at work, and I can say it again suffers from being not quite as nice as the japanese models though still miles ahead of cheap chinese models


Quote
I know I want the thumbwheel (any reason why I wouldn’t want it?),
I find a thumbwheel easier to use when trying to move the calipers a short distance or back and forth over a measurement.  My 12" calipers do not have a thumbwheel and I find it much better when I'm sliding a long distance, but trying to get right to final measurement is a little more finicky.
Quote
and ideally bigger digits. I also know the standard 6”/150mm is more than enough for me at the moment.
If you can I would recommend an 8".  It can be surprising how often just a little more measurement space will help, and they're not nearly as big and ungainly as a 12"
Quote
I also don’t see any need for a data link. But what else should I look for? I assume IP67 rating keeps dust out and theoretically improves longevity, right?
IP67 is waterproof for keeping coolant from machining out.  For regular use this isn't really needed
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What about jaw shape?
Unless you know you need something funky go with the standard common jaws
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Micrometer resolution?
I don't trust a caliper to tighter than .002/.003" really so I wouldn't spend extra on anything tighter than the commonly available half thou readout.
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Square vs round depth gauge?
round fits in more spaces but is more easily damaged.
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Carbide jaws? (Expensive!)
Really nice for high precision kind of a waste on calipers imo.
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[Edit: since it doesn’t seem to be clear, I’m expressly asking for help evaluating which of those features make sense, because the range of models is overwhelming.]

Some models list “inductive” sensing. Others “absolute positioning”. What should I look for?
absolute is less prone to the jumps that have been bugging you, but on any higher end caliper this really should not be a problem.
Quote

For what it’s worth, I was using a mitutoyo recently and, just like the instructor warned me, it was hella easy to accidentally hit the hold button and thus inadvertently not take a new reading at all. Didn’t like that button layout.

They’ve also got some sets on sale, with a caliper, micrometer, and various metalworking tools. I don’t think I need a micrometer, but is it worth having?
If you don't need to measure something solid to a tolerance of less than .002/.003" micrometers aren't really going to do anything for you, especially since you will need several just to cover a small range. 
Quote

My actual needs are modest. I’m measuring mostly things like screws, components, cutouts, etc. But I absolutely hate using shitty tools, I want something dependable and that feels good in my hand, where the parts slide smoothly without wobble, with great usability.

So, any advice? Unfortunately, I don’t think there’s any opportunity to try before buying, nor any real return period, so I hope the hive mind can help me out! :)

Thanks in advance!


I think I answered as many of your questions as I could.  I'm not an expert by any means, I'm just a machinist who uses these tools every day so I have some opinions.  My general advise would be to make sure you want a digital caliper over something like a dial caliper.  I personally find the dial caliper easy to trust since I don't have to worry about batteries, or if I pressed the wrong button or anything else.  Obviously some people will really prefer the general ease of use reading a digital caliper so that's up to you. 

Based on what you've posted for your needs I wouldn't waste money on fancy features since pretty much any "name brand" is going to have the general feature set to make you happy.  Most of my measurement tools are older American or newer Japanese so I can't comment on European manufactured items too much.  I do have a couple swiss made dial indicators and I have found them high quality and smooth operating, but they always feel more fragile to me so I wouldn't recommend them as a main tool to be used and abused every day, but they are the ones I bring out when a measurement just HAS to be right. 
« Last Edit: July 18, 2018, 01:08:18 am by vltr »
 
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Offline eKretz

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Re: Digital calipers — what to buy?
« Reply #30 on: July 18, 2018, 03:07:51 am »
Ok, more specifically: the thumbwheel is nice for fine adjustment,  but also makes it VERY easy to apply too much pressure.  I do like them on smaller calipers for sure.  Jaw shape is kind of a non-issue unless you're measuring into tiny grooves, and even then much of the time. Tungsten carbide jaws are great,  but not necessary for someone who's not measuring steel every day all day. For someone not doing production work like that the hardened steel jaws will last indefinitely. Please do not use your calipers as a scribing tool, that is definitely not what they're intended for. Even the guys who do this will admit it eats the jaws up. Also avoid trying to measure sharp edges like on hardened cutting tools unless you use caution. Round vs. square depth rod has never really mattered to me. I have had calipers with both and there's not much difference except that the round rod can occasionally get into places (again,  some small grooves) the square one can't.  My personal preference is for the square/ rectangular rods - the round ones always seem to warp more often.

Calipers aren't meant to be precision measuring tools. They will get you close,  but they're not micrometers. If you're careful and you know what you're doing,  you'll get within .001" - .002" - sometimes closer.  The temperature change and resultant expansion when you hold the bar in your hand hurts caliper accuracy,  and so does the necessary slop to let them slide freely. Any additional pressure hurts it even more.
 
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Offline KE5FX

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Re: Digital calipers — what to buy?
« Reply #31 on: July 18, 2018, 03:29:04 am »
Look for a (genuine) Mitutoyo CD-8.  It addresses basically everything on your list... awesome quality, perfect ergonomics, plenty of length (8"/200mm), recessed zero and origin buttons, nice large digits.

It has an ON/OFF switch, but I never use it.  I leave it on all the time, and I still get 2+ years of battery life.  If I were to turn it off, I imagine the battery's service life would basically be equal to its shelf life.
« Last Edit: July 18, 2018, 03:33:58 am by KE5FX »
 

Offline KL27x

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Re: Digital calipers — what to buy?
« Reply #32 on: July 18, 2018, 03:36:56 am »
If your calipers are skipping 0.1" here and there, it's possible your calipers are dirty. Doesn't matter if they're Mitutoyo or $10.00 calipers. Grease or dirt can skew the reading by changing the capacitance. Bad enough, and maybe the micro gets confused. The other potential issue is slow wakeup. If they are the kind that turn on automatically when you move them, maybe you are just moving them too fast from sleep. I always check they're zeroed after turning them on, anyway.

I use the silver oxide batteries in my cheap calipers. I use them all the time. I probably change them no more than once a year. Maybe every other year?

The main issues I have had with the cheap stuff are minor quibbles for my own needs. The battery case might be a little shiite, so that the meter turns on/off by itself. This is a pretty easy fix. Roughness in the movement is another thing you sometimes get. But I have 2 calipers that cost about $10.00 which are smooth as anything and very solid. Never had any problem like you had with your Aldi, except that they can get flaky when the battery is dying. Just had to futz with the cover on the one, and I dropped and broke the glass on one; still works great. It's a bit of a gamble, but if I bought 4 cheapo pairs from 4 different vendors, I'd probably have at least one excellent pair of calipers and 4 perfectly usable tools. 

I keep a caliper at the electronics bench, and 3 more in the garage in spots where I use them. By the sander and routing table, next to the shooting board, etc. I'd rather the cheap one where I use it than one "good" caliper in a padded case.

Come to think of it, the erroneous reading thing was a small but real, nagging fear before I switched to the silver oxide LR44. Aside from simply lasting much, much longer, I think the silver oxide produce a more flat voltage and don't screw with the microcontroller so much at their end.  These should be standard fare for calipers.
« Last Edit: July 18, 2018, 04:32:03 am by KL27x »
 

Offline CatalinaWOW

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Re: Digital calipers — what to buy?
« Reply #33 on: July 18, 2018, 05:01:34 am »
Another vote for dial calipers.  Easy to read, infinite battery life.  If you aren't logging your measurements there is little advantage to the digital units.  I have several digitals, which rarely get used while the dial calipers are used daily. 

Features - I agree on thumbwheel, and locking set screw.  These are almost universal so not really a selection feature, except to reject a few outliers.  If you need precise hole diameters a head designed for that helps, but the standard head shape is better for most uses.  If you are doing that much hole work you probably need to invest in another set and then use the appropriate one for each thing. 

For electronics uses I haven't ever seen anything which would drive a preference on depth gauge configuration.  The 150 mm/ 6 in size meets most needs and is convenient to handle and store, but there is always something that wants a bigger range.  Unfortunately prices really rise and the larger sizes are unhandy for smaller jobs.
 

Offline JonM

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Re: Digital calipers — what to buy?
« Reply #34 on: July 19, 2018, 04:36:35 am »
My primary calipers are Mitutoyo but I also have several SPI "Swiss Made Plastic Dial" calipers which are lightweight, and non-conductive which can often be useful.

I have not yet changed the batteries in the Mitutoyo after several years, even after putting it away with the power on several times. I have some Harbor Freight digital calipers that burn through batteries while sitting unused.

 
 

Offline Fsck

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Re: Digital calipers — what to buy?
« Reply #35 on: July 19, 2018, 04:45:25 am »
I use dial calipers because I keep forgetting to get new batteries for the digital ones.
I use some old Fowler NSK made in Japan ones I got off kijiji (canadian craigslist, etc)
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Offline KL27x

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Re: Digital calipers — what to buy?
« Reply #36 on: July 19, 2018, 09:58:54 am »
It's ironic that electrical engineering types can't be bothered with batteries. It's a given that I have CR2032 and silver oxide LR44 (and probably 12 other kinds of batteries) in a box at my electronics bench.
 

Offline David Hess

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Re: Digital calipers — what to buy?
« Reply #37 on: July 19, 2018, 10:11:45 am »
I think it is more of a problem that battery life is so short with other than the best calipers.  After you get through Mitutoyo's web site, you can find their operating life specifications in *years*.
 
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Offline KL27x

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Re: Digital calipers — what to buy?
« Reply #38 on: July 19, 2018, 11:32:23 am »
1-2 years seems pretty reasonable to me. This is what I get with the silver oxide batteries. (6 months maybe on alkaline.)

I've a depth gauge (same old thing as regular digital calipers, really, just a different shape) that takes CR2032. I'll be curious to see how long it lasts.

My pen DMM probably eats a CR2032 per year. Small price to pay for the ergos.

Smoke detectors? Watches? Yeah, I don't like changing batteries in those, for some reason. But I don't think I'd buy $100.00 smoke detectors that last 3x as long per 9V. But, meh. Maybe if it were made in Germany or Japan it would be worth it. :)

Now I'm curious. For $100.00, do Mitutoyo calipers ship with an alkaline battery or a silver oxide? The difference is enormous. There's a crapton of energy left in an alkaline by the time a single cell can no longer power a micro. It's a curious design choice. There are dozens of 3V button cells that are smaller and would last several times longer.
 
« Last Edit: July 19, 2018, 11:57:19 am by KL27x »
 

Offline eKretz

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Re: Digital calipers — what to buy?
« Reply #39 on: July 19, 2018, 06:09:36 pm »
If you get a good pair of digital calipers and don't use them all day every day, battery life is NOT even relevant. I have a set of Mitutoyo calipers that I use all the time that have been on the same battery for nearly 7! years. I will change the battery soon, the display is starting to get dim. Mitutoyo is absolutely the best on battery life that I have used.
« Last Edit: July 19, 2018, 06:12:04 pm by eKretz »
 

Online HighVoltage

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Re: Digital calipers — what to buy?
« Reply #40 on: July 19, 2018, 06:23:27 pm »
Mitutoyo is absolutely the best on battery life that I have used.
They are the best, when it comes to battery life!

It really does not matter much, if you leave a Mitutoyo ON of OFF, the battery will last about the same.
The ON/OFF switch is just for "feel good".



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Offline bitwelder

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Re: Digital calipers — what to buy?
« Reply #41 on: July 19, 2018, 07:00:54 pm »

The calipers I use all day long are. iGaging ABSOLUTE Origin.

 https://www.amazon.com/iGaging-ABSOLUTE-Digital-Electronic-Caliper/dp/B00INL0BTS


One more vote for the iGaging. For me they are a good middle-ground between the top class Mitutoyo and the crappy Chinese clones.
 

Offline KL27x

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Re: Digital calipers — what to buy?
« Reply #42 on: July 19, 2018, 07:32:17 pm »
Quote
It really does not matter much, if you leave a Mitutoyo ON of OFF, the battery will last about the same.
This has been stated at least 3 times.
No one uses the off button, on any calipers, do they?

And yes, it does make a difference, technically. But for most users, the calipers will spend 1000x more time in sleep than actually on. The improvement in battery life between a Mitutoyo and a cheap chinese calipers is mostly due to lower sleep current. This has been measured and demonstrated. I don't recall the actual figures, but it is several fold difference in sleep current draw. This is not remarkable. If you compare sleep current between different micros, you can find many fold differences.

There is a new wave of large digit cheap chinese calipers. I wonder if they use the same micro. I avoided buying them because for a lot of small things I think in thou, and the big digit displays have the big digits only down to hundredths and a small digit for the thou and the half... irritating.

I would bet $2,000 that iGaging uses the exact same pcb's, circuitry, and micro as any $10.00 caliper. They might have better quality control as far as the polish and fit on the steel bits.

As far as accuracy of a digital caliper, it comes down to the accuracy of a printed circuit board glued onto a bar of steel. Even if mit's are higher in quality control, that means maybe 90% of cheap calipers would be exactly as accurate. It would be important for (some) professional machinists the way a calibrated 6 digit meter is important to (some) electrical engineers. For me, if it matters, there's the mitty. If it doesn't, there's not much purpose of the "middle ground" (re)brands. If you don't have a mill or metal lathe and regularly use a set of pin gauges and 1-2-3 blocks, you will never realize a difference. Even if you're a pro machinist, the main benefit for you is that when you do inevitably mess up your job (for unrelated reasons), no one is going to see you standing there holding a pair of $10.00 calipers. A machinist need mittys for the same reason a mechanic needs a steel tool chest covered in stickers and a lawyer needs to wear a suit in court. Or an EE needs a JBC or Metcal. :)

The fact that the battery life is a major selling point is weird to me. A smoke detector that lasts 30 years would improve my life way more than Mitty calipers. But no one is going to rave about a smoke detector and not many would pay 10x as much for one. 

Keep in mind... silver oxide LR44. If you're not using it, you're doing it wrong.
« Last Edit: July 19, 2018, 09:23:24 pm by KL27x »
 
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Offline KE5FX

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Re: Digital calipers — what to buy?
« Reply #43 on: July 19, 2018, 10:17:18 pm »
As far as accuracy of a digital caliper, it comes down to the accuracy of a printed circuit board glued onto a bar of steel. Even if mit's are higher in quality control, that means maybe 90% of cheap calipers would be exactly as accurate. It would be important for (some) professional machinists the way a calibrated 6 digit meter is important to (some) electrical engineers. For me, if it matters, there's the mitty. If it doesn't, there's not much purpose of the "middle ground" (re)brands. If you don't have a mill or metal lathe and regularly use a set of pin gauges and 1-2-3 blocks, you will never realize a difference. Even if you're a pro machinist, the main benefit for you is that when you do inevitably mess up your job (for unrelated reasons), no one is going to see you standing there holding a pair of $10.00 calipers. A machinist need mittys for the same reason a mechanic needs a steel tool chest covered in stickers and a lawyer needs to wear a suit in court. Or an EE needs a JBC or Metcal. :)  The fact that the battery life is a major selling point is weird to me. A smoke detector that lasts 30 years would improve my life way more than Mitty calipers. But no one is going to rave about a smoke detector and not many would pay 10x as much for one.  Keep in mind... silver oxide LR44. If you're not using it, you're doing it wrong.

Actually I use every bit of the precision and accuracy I get from the Mitutoyo, and could even stand more.  Measuring the core thickness on a 6-layer board under a microscope is a job for more specialized tools, but lacking those, the calipers had better be good.

It's also used frequently to identify features that show up in a high-resolution TDR plot.  The quality isn't as critical there but the 8" length comes in handy.  And of course I benefit from the battery life every time I use it without having to replace the battery first.

Definitely a good idea to keep a good pair and a crappy pair around, so you're not tempted to use one where the other is called for.
 

Offline KL27x

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Re: Digital calipers — what to buy?
« Reply #44 on: July 19, 2018, 10:26:41 pm »
Quote
Measuring the core thickness on a 6-layer board under a microscope is a job for more specialized tools, but lacking those, the calipers had better be good.
I hate to be that guy, but the cheap calipers are going to give you the same reading as your Mitutoyo on that small of a measurement. Down to maybe one blinks the half thou or not. If you could remove all human error and material compression/surface finish error, you would have that same issue between 2 pairs of Mitts, given the thing being measured might fall right on the fence.

Quote
It's also used frequently to identify features that show up in a high-resolution TDR plot.  The quality isn't as critical there but the 8" length comes in handy.
this is where you might see a significant (and repeatable) difference, at the long end of the scale. Due to cumulative pcb printing error and/or pcb warpage. This is where Mitt will actually ( I bet) test and discard in QA. But this is where you say the precision isn't as critical. So a cheap caliper might have 1 mil offset per inch you go. 

Quote
And of course I benefit from the battery life every time I use it without having to replace the battery first.
Yes, this is undeniably true. You got that one right.
« Last Edit: July 19, 2018, 10:42:45 pm by KL27x »
 

Offline KE5FX

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Re: Digital calipers — what to buy?
« Reply #45 on: July 19, 2018, 10:55:13 pm »
Quote
Measuring the core thickness on a 6-layer board under a microscope is a job for more specialized tools, but lacking those, the calipers had better be good.
I hate to be that guy, but the cheap calipers are going to give you the same reading as your Mitutoyo on that small of a measurement. Down to maybe one blinks the half thou or not. If you could remove all human error and material compression/surface finish error, you would have that same issue between 2 pairs of Mitts, given the thing being measured might fall right on the fence.

Sure.  And the next time I make the measurement, will I get the same number?  How about the time after that?  When I glance away from the microscope to view the caliper display, how much did the cheap mechanism move... whether I tightened the locking screw or not?

When verifying PCB layer thickness with calipers, you don't use compression.  If you apply any force at all, you'll never be able to make accurate, repeatable measurements.  Instead, you focus the scope on both the layer under inspection and the caliper jaws at the same time, opening the caliper carefully to produce a matching gap.  You're measuring distances very close to zero, and you need at least 10x the final precision of the measurement you're trying to make.  How often does a cheap pair of calipers produce a repeatable zero down to 10 micrometers, anyway? 
 

Offline KL27x

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Re: Digital calipers — what to buy?
« Reply #46 on: July 19, 2018, 10:58:49 pm »
Quote
Sure.  And the next time I make the measurement, will I get the same number?
IME, yes. IMO, cheap calipers are more than likely just as repeatable as a Mitt. It's the absolute accuracy at longer distances where the Mitt is going to prove its worth. The way they measure is pretty much exactly the same and depends on the accuracy of the capacitative pads on a PCB, and last I checked Chinese PCB manufacturers know how to make pcb's.

The only time I can get a different reading is if there's grease on the caliper. Other than that, all my calipers are perfectly repeatable down to the last thou. Wipe the jaws off, wipe the bar off, zero, and hold the same way on a smooth, rigid object? Perfectly repeatable. 

I have used them to machine dies where precision must be within a thou. They work. Every time. First time I did this, I had to constantly measure my reference object for peace of mind. It is hard to believe how repeatable a $10.00 caliper is. It took time, but now I trust them implicitly to a thou... more accurate than you can even get unless you take the time to go through that little ritual of cleaning the calipers and all. If I order precision made part under an inch or so, I will either measure the exact number down to the last mil, or the supplier got it wrong.

If I measure 401 thou on a steel rod 9 times out of ten, and 401.5 one out of ten (due to surface irregularity), today, it will measure the same thing tomorrow and the day after and it will measure the same with all of my calipers.

If you need precision beyond a thou, a Mitt won't do that, either. If you're a machinist asked to make something 4" long to tolerance of a thous, then you want a Mit.
« Last Edit: July 19, 2018, 11:58:29 pm by KL27x »
 

Offline eKretz

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Re: Digital calipers — what to buy?
« Reply #47 on: July 20, 2018, 12:32:22 am »
No they aren't just as repeatable. The materials used, the finish on the ground steel, the tolerances hit or missed, the squareness and parallelism of the ground surfaces etc. etc.  These are all areas that hugely impact accuracy and repeatability. They are also excellent on a quality caliper and terrible on many of the cheap Asian imports. And yes, I HAVE measured and checked repeatability. Many of the cheap calipers also will move when locked, as well as change the jaw angle so that they are no longer parallel. They may also measure a different size if you check up near the bar vs down near the end of the jaws. The good calipers suffer none of these issues. The cheap brand do not worry so much about quality control and accuracy, as evidenced by many cheap junk products on offer. I have personally bought plenty of Chinese Junks and been disappointed by many. Every now and then you get something decent though.
« Last Edit: July 20, 2018, 12:39:29 am by eKretz »
 

Offline KL27x

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Re: Digital calipers — what to buy?
« Reply #48 on: July 20, 2018, 12:42:16 am »
Quote
the squareness and parallelism of the ground surfaces etc. etc.
This is debatable if it even qualifies as repeatability. If you measure the same way on the same place on the jaws, this doesn't have an effect.

That said, I have not found any problem in this area with my calipers that makes a significant effect. Significant with respect to the resolution at hand. I have noticed no problem in 3 sets. Considering I drop them and use the tips to scribe stuff, I don't know that it would matter. And as far as parallelism or evenness of the jaws, I am fully capable of stoning a set of steel jaws if I needed to. When you need a measurement down to a thou, you can't expect to get an accurate reading by clamping down with significant force, anyway. Of course this will flex even a Mitutoyo.

One set of calipers I have has a unique solution to the fit between the sliding bars. It rides only one one side; there's a leaf/bar spring to keep the parts on the one direction to take out play/slack. This one was very rough in movement (pretty decent after some buffing). My other two sets don't have this feature (that I recall since looking inside), but they slide tight and buttery smooth. And we're talking 6" of interface, which is enormous. (Maybe opened beyond 4"+, the precision of mating will become significant).

We have different experience. All my calipers are repeatable. And as far as absolute accuracy*, I have purchased several precision dies and materials and they always measure exactly as advertised. I even have developed suspicion that when machinist makes a steel rod/shaft specified to a thousandth, that he always makes the MAX diameter to that spec. Probably to avoid complaints that it doesn't fit. The average reading I get in this particular type of case is typically half a thou low.

I believe some people have a bad experience. I'm 3 for 3; I think it's probably a pretty good gamble. Esp if you can read current reviews for the thing. On mine, not wiping off the jaws has more effect on reading than any issue you described. Maybe it would be faster or easier to use the Mitutoyo (incorrectly/sloppily) and get the right reading? Dunno. I have no need to find out, up to now. A 0.400" rod and a 0.401" are worlds apart for certain things I have done. And my $10.00 calipers easily discern the difference, repeatably, and unambiguously... both relatively and absolutely with no need to reference against a pin gauge. How much better can a half a thous resolution device get than that, I have to wonder.

*And why wouldn't they be abolutely accurate? There's just a repeating pattern on the pcb/slide. Then the measurement is relative to where you zero it.
« Last Edit: July 20, 2018, 02:59:48 am by KL27x »
 

Offline eKretz

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Re: Digital calipers — what to buy?
« Reply #49 on: July 20, 2018, 03:02:48 am »
So you've been exposed to 3 sets of calipers? I've seen hundreds. Used to work at a place with 150 machinists. And the whole point of accuracy in construction of a caliper in terms of that squareness and parallelism is so that you don't have to measure in exactly the same place twice. I guarantee you're not doing that with your calipers in most cases. Unless you've got a scribed alignment line on the jaw that you're lining up with a microscope every time you make a measurement?

Regardless, this is mostly academic, as calipers just aren't that accurate to begin with. But why not do everything possible to make them as accurate as they can be? The cheap companies don't do that, and let all kinds of garbage through that would get bounced in a heartbeat at any reputable company - like coarsely ground surfaces that need to be stoned to smooth the sliding surfaces. And stoning the jaws will NOT correct geometry errors. That takes actual substantial metal removal, i.e. grinding. Your 3 pairs may be decent, but they produce hundreds of thousands of pairs, and I have seen plenty that are NOT up to snuff. When you buy cheap junk, what you get is basically a roll of the dice.

As far as your implication that I don't know how to use a measuring tool like a caliper as well as you do...I honestly have no words. How many machine shop have you worked in and for how many years?

Being that I actually made precision devices and machinery for a couple decades, I recognize poor craftsmanship when I see it. For things that I use while pursuing my livelihood, I want good quality tools that make my job easier, not those that I need to worry about. Personally I appreciate the good quality work that goes into better tools, and they are almost always far more pleasant to use. And for the relatively inconsequential difference in price for something like a caliper, IMO it's silly not to get something good. YMMV, and that's fine.
« Last Edit: July 20, 2018, 03:06:03 am by eKretz »
 


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