How Accurate Are Low Cost Digital Calliper Micrometers?

[Will RobertsonParticipant @willrobertson16447]

There are digital micrometer callipers available now very economically – I bought mine on Ebay, a few months later a large supermarket chain started selling them as well (albeit at higher cost), I noticed that Model Engineer are now giving them away as a free gift for new subscribers. They all look similar although the manufacturer isn't named.

Has anyone tested how accurate these are? The literatures with mine says "Accuracy: +- 0.02mm/0.001in (<100mm) +- 0.03mm/0.001in (>100mm)" and "Repeatability: 0.01mm/0.0005in".

To independently verify their accuracy I think it would be necessary to compare them to certified precision standards or an instrument with certified calibration but I don't have access to either of these.

The last time I used callipers they were read via a Vernier scale an the electronic version was considered an expensive luxury…

[Will RobertsonParticipant @willrobertson16447]

[Ian S CParticipant @iansc]

Will, put measuring in the keyword window, and click all topics, and you will find a discusion on the subject. Ian S C Can't remember how to transfer you to the site any easier sorry.

[Douglas JohnstonParticipant @douglasjohnston98463]

Provided the mechanical parts are well made they seem to be fine. I have an expensive Mitutoyo calliper and a couple of cheap Chinese ones and they all give the same reading within a thou. The Mitutoyo one has a smoother action and feels a bit more refined but was ten times the price.

I tend to use the cheap ones for all rough work and keep the expensive one for better work. I have often wondered how the Chinese can make these callipers at the price they do considering the work that goes into making them and with the use of hardened stainless steel for the body.

Doug

[CHRIS WOODS 1Participant @chriswoods1]

They regularly passed the relevant third- party calibration measurements (traceable to National Standards) and certificates were issued by the firm that undertook the calibration in confirmation as part of the ISO 9001 quality system in the mechanical engineering company where I worked.

With this type of digital caliper it's more important for model engineering home use to recognize their shortcoming in other senses, e.g. they don't have a fine feed adjustment -in the small size units anyway, which helps to achieve a correct size measurement by 'feel' and hold it while you read the display.

Basically it's more down to knowing how to use it rather than criticising, say, the electronics, the embedded scale, or the construction of the unit. Mechanically I find them very good. If you drop one and bend a jaw, throw it away and purchase another bargain one.

[John Stevenson 1Participant @johnstevenson1]

If you are working to a tolerance of 1 1/2 to 1 thou plus or minus they work fine.

Better than this you need to switch to a micrometer.

I use them all the while to get close then swap the micrometer. At the moment we have never had it so good, ARC for one is doing these at £8.00 a pair and to be honest at this price they are consumables.

My first set of digitals cost £123 when I was on about £40 a week wages. I have recently replaced some of mine because of being tatty, chip burns on windows etc and treated myself to 6 new pairs.

John S.

[David LittlewoodParticipant @davidlittlewood51847]

Will,

See discussion in this thread:

http://www.model-engineer.co.uk/forums/postings.asp?th=56666&p=2

– see posts on 2/11/2011, about 2/3 way down.

David

[David Clark 13Participant @davidclark13]

Hi John

6 Pairs.

Does this mean you take 1 day a week off?

regards David

[Ex contributorParticipant @mgnbuk]

I have checked a couple of sets of Lidl / Aldi digital calipers against slip blocks & found there to be no difference in readout accuracy to more expensive brands used at work.

I find it amazing that these devices can be retailed so cheaply – the quantities manufactured must be incredible. I paid more for a Polish vernier caliper 15 years or so ago than the digitals sell for today. Mind you, the vernier caliper continues to work when it is cold – the downside is the need these days to require a magnifying glass to read it !

Nigel B.

[Sub MandrelParticipant @submandrel]

NIgel,

Mine (I only have four John…) tested out with similar results on the 1" slip provided with my 2" mike.

Of late one of them is reading slightly out – experience says that means clean the body really well.

Neil

[Speedy Builder5Participant @speedybuilder5]

I have a low cost caliper, problem is that the battery drains away when not in use. I can't get much more than 6months out of the battery – unless I take it out each time! Anyone else have this problem ?

[John Stevenson 1Participant @johnstevenson1]

That's about 2 pence per week – how long does it take you to remove it.?

[Ady1Participant @ady1]

I've used one fitted to my cross slide for the last year so it's done plenty of work

It switches off when not in use, and stores the reading which can be very handy when doing a long job.

At a tenner a pop I'm quite amazed at how good they are

Great for threading work, simply add a few hundredths of a mm for each pass, backlash measurement issues are now a thing of the past so you can thread under constant power, set the number yank in the clutch and away you go

Push a button and go from metric to imperial too. Amazing.

[Will RobertsonParticipant @willrobertson16447]

Many thanks – good to know!

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

I has digital caliber with imperial both in 1/1000" and fractional imperial (button with mm, 1/1000", fractional imperial). Learned out the fractional imperial measure is not to rely on at the digital caliber. There is a gap in fractional imperial measuring when i compared with 1/1000" in the digital caliber. Better to use 1/1000" or use caliber without electronic digital measure when fractional imperial is used to get exact measure of the product. For each measure, set at zero before use to be sure the measure is correct as possible. Remove dirt from measure jaws before measuring at the product.

Also i am using imperial measure as showed in the drawning while i am working with the Stuart Turner compound steam engine.

[Sub MandrelParticipant @submandrel]

I made a disply for the DROs on my mill and added fractional measures as a 'feature' just to see if I could. The problem is that, as you don't want to go down to 1/1024", but just 1/64 you can be up to 1/128" out. If you use too small a fraction the display changes very quickly and in a confusing way.

I got around this by lighting an indicator to show when you are within 0.002" of the indicated fraction(I decided that if I'm using fractions then that is accurate enough).

Neil

[Jens Eirik Skogstad 1Participant @jenseirikskogstad1]

Yeah, right.. there is a little dumb idea when the digital caliber do not have the 1/128" fraction when we are talking about precision measuring to example the fit between two parts must be exact and tight. Will one come to 1/128" in fraction then turn over to 1/1000" in decimal ( 1/128"=0,0078" ), let us say the product must be 15/128" then the measure will be 0,1171"

Edited By Jens Eirik Skogstad on 24/04/2012 22:43:44

[John Stevenson 1Participant @johnstevenson1]

It's a step backwards putting fractions on measuring instruments.

Name one precision machine that has the dials calibrated in fractions ?

Wood working equipment doesn't apply, they are only made for wood butchers.

John S.

[Gordon WParticipant @gordonw]

Ok, not a precision machine, but I have an Indicating Caliper, made by The Indicating Caliper Co. of New York, this is marked in 1/64" and can easily be read to half that, so 7 thou'. How much better do you want for a casting? BTW these are used for measuring castings and forgings as no other instument can.

[NJHParticipant @njh]

Hi John

" It's a step backwards putting fractions on measuring instruments.

Name one precision machine that has the dials calibrated in fractions ?

Wood working equipment doesn't apply, they are only made for wood butchers."

Maybe you've hit on the answer. These calipers as so cheap now that they are accessible to everyone. Why wouldn't a woodworker (or anyone else not requiring high precision measurement) not find them useful? If you are used to working in fractions of an inch then 9/16 probably means something whereas 0.5625 may not.

I must say though that I recently bought a cheapo digital scale & readout for the mill and was a bit surprised when that too offered metric, imperial and imperial fractional output!

( Oh and don't knock the "wood butchers" – without them you would probably have to sit, sleep and eat your meals off the floor! )

Regards

Norman

Edited By NJH on 25/04/2012 10:44:37

[Ian S CParticipant @iansc]

Putting the fractions on measuring gear, is something like what happens with LED tail lights for bikes, mine has on, and flashing, cheaper ones have on and five different flashing patterns just because they can. Ian S C

Edited By Ian S C on 25/04/2012 13:36:27

[TerrydParticipant @terryd72465]

Posted by NJH on 25/04/2012 10:44:13:

Hi John

" It's a step backwards putting fractions on measuring instruments.

Name one precision machine that has the dials calibrated in fractions ?

Wood working equipment doesn't apply, they are only made for wood butchers."

Maybe you've hit on the answer. These calipers as so cheap now that they are accessible to everyone. Why wouldn't a woodworker (or anyone else not requiring high precision measurement) not find them useful? If you are used to working in fractions of an inch then 9/16 probably means something whereas 0.5625 may not.

I must say though that I recently bought a cheapo digital scale & readout for the mill and was a bit surprised when that too offered metric, imperial and imperial fractional output!

( Oh and don't knock the "wood butchers" – without them you would probably have to sit, sleep and eat your meals off the floor! )

Regards

Norman

Edited By NJH on 25/04/2012 10:44:37

In a cave .

Don't knock fractions, not all engineering needs 0.001mm. Try building a bridge without using fractions. Engineering is not just about machined components.

Seriously, the system of measurement should fit the need of the component. An extreme example I saw recently was a motor mount which was dimensioned as 3.4375" overall length. This implies extreme accuracy whereas a fractional dimension of 4 7/16" would have been accurate enough as it is not a critical dimension. Horses for courses.

Regards

T

[John Stevenson 1Participant @johnstevenson1]

They only exist in Imperial measurement. 1/2 a metre isn't a technical term.

[Speedy Builder5Participant @speedybuilder5]

Whilst knocking the use of fractions, why don't we jibe at number and letter drills ? For us IMPERIAL lot, did any one see drill and reamer sizes in decimal increments – Oh yes please, can I have a 0.35" dia drill. Fractions, letters and numbers are the bread and butter of many of our old drawings as too are milimeters for newer drawings – so don't knock it when us traditional enginers use a bit of modern metrology to connect with the past.

[Anonymous]

Hmmmm, what a vulgar discussion, let us hope it stays rational and proper, and doesn't veer into the improper.

Regards,

Andrew

[Author]

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