digital calipers

[Robin teslarParticipant @robinteslar]

Hi Myfordians

Im sure we are all aware of the plethora of cheap digital measuring devices available on Ebay all from PRC of course. The probelm I find with my digital caliper is that the zero can inexplicably change, sometimes quite drastically in the course of measuring. Of course I make it a habit to close and zero the reading each time (essential imho) but it certainly detracts from the usefulness of the device and that you could end up with scrap if you forget to check zero each time. Course, never got that with a vernier caliper.

I understand the basic the simple micro slice scale that it uses (is it optical?) and that it is inherently relative, but there are better systems that use an absolute scale. Can anyone suggest a caliper like this (Mitutuyo? serious cost)

Certainly I couldnt possibly trust this system for any machine mounted DRO

Am I missing something, should i go back to my vernier caliper and get much stronger spectacles

Robin

[Robin teslarParticipant @robinteslar]

absurdly cheap but?

[Nick_GParticipant @nick_g]

Posted by Robin teslar on 13/01/2015 11:41:24:

Hi Myfordians

Robin

What shocking disgraceful discrimination.!

Boxonians and Chinglites have equal rights these days you know.

Nick

[Neil WyattModerator @neilwyatt]

Hi Robin,

The scale is capacitive. Most cases of varying readings I have seen can be resolved by cleaning the scale carefully with meths or changing the battery.

Zero readings can drift overnight on the calipers, but I haven't found this with DROs. The heads are identical, so I think it may be something to do with leaving calipers closed when the temperature cycles overnight? It is also possible to tap the zero button when closing the caliper if I'm a little careless.

For the price I consider them disposable, but I've never had to throw one out and some of mine are well over twelve years old old.

It's worth making sure you don't have the real cheapies – go for stainless steel reading to 0.0005"/0.01mm and loom for the thumbscrew at the top for adjusting the gib.

If you have a duff one, try again, I have five or six calipers (including a couple of plastic 'hacks&#39 and three DROs, only one (a DRO on the mill) has totally failed (I got a new read head for very little from Machine DRO). I remember using my vernier caliper once, but it was a long time ago.

Neil

[Gray62Participant @gray62]

Robin,

I've used the el-cheapo calipers (and still do from time to time) but now only ever for a rough guide. For final measurement, I always refer to either a Moore and Wright digital vernier which is far more reliable or traditional micrometer and or vernier or dial gauge caliper.

I find that temperature and humidity can have significant effects on the cheap digi calipers.

For reading, as I have poor eyesight, I invested in some clip on loupes, at around £40 they give 3.5x magnification which is ideal for reading a vernier and when not in use simply flip up out of the way.

Graeme

[mechman48Participant @mechman48]

Hi Robin

This applies to all of us not just Myfordians; As you say to have a decent readout you have to 'pays your money' i.e. Mitutoyo, all these digi callipers are made for the mass market in PRC & sold under many brand names inc. Starret, M&W etc. I have a 8" Mitutoyo digi vernier, & 0 – 25 mic that I use as masters, I use a 3" & 4" digi verniers for general use ( from Machine-DRO UK, usual disc. ) again made in PRC, but I also have a couple of 'older' analogue mic's inc. one I bought when I served my apprenticeship so its over 45 yrs old, & still accurate, some of which I use to double check a final reading on stuff I am doing ( not a lot lately ) .

What I find is that for consistent readings I leave my mic's / verniers to 'acclimatise' to my workshop temperature once I have had the heaters on for about an hr, or I have a vernier in my top pocket where it reaches body temp so as I use it it maintains repeatability, & yes I still check 'zero' occasionally. The trouble with batteries is that when cold they tend to have a voltage drop until warmed up so keep them at a constant temp if you can.

George.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Robin teslar on 13/01/2015 11:41:24:

… should i go back to my vernier caliper and get much stronger spectacles

.

Robin,

A very useful compromise would be the type with a rack driven dial [instead of a digital display, or a vernier].

… My old Mitutoyo still reads reliably [provided I keep the rack clean]

MichaelG.

[Ralph HParticipant @ralphh]

Digicals are all the rage now. Half the people at work cant even read a mic.

I have many on my calibration system and I wouldnt trust them to within a thou let alone 0,01mm. The cheap ones certainly do "drift" very easily. Most of the time the cause is swarf or dirt on the tracks and they all need regular cleaning with meths to flush out the tracks. Even a tiny amount can throw the reading out of accuracy (not just at zero either) and the cheaper the caliper = the more sensetive to it they are. It is a case of you get what you pay for here and Mitutoyo make by a long way the best and most reliable. Not totally proofed againt drift but much much better. Someone here recently bought a cheap one from SPI and it couldnt even hold a zero out the box. I flushed that and it was dirty from manufacture. Even after that it wasnt great and is now marked with a 'do not use'.

I use mics or verniers and dont trust them in general, much prefer my eye. Buy a Mitutoyo. They are worth the money.

[Robin teslarParticipant @robinteslar]

Posted by Michael Gilligan on 13/01/2015 12:56:54:

Posted by Robin teslar on 13/01/2015 11:41:24:

… should i go back to my vernier caliper and get much stronger spectacles

.

Robin,

A very useful compromise would be the type with a rack driven dial [instead of a digital display, or a vernier].

… My old Mitutoyo still reads reliably [provided I keep the rack clean]

MichaelG.

Thats a very sound suggestion, will look into it tx

[Neil WyattModerator @neilwyatt]

Am I being cynical to think that having to clean digital calipers carefully is a 'design flaw' but when it come to the rack type, it's 'good care'?

Neil

[Robin teslarParticipant @robinteslar]

Allow me to say, guys, that the anomalies that i observe are more like step changes say 0.15mm instead of zero. not consistent. My caliper is gerally clean, but will try some spirit. I think it has more to do with the speed at which i close to re-zero the device, maybe it cant keep up, not that i am rash of course.

A salutory observation I think. One step forward two steps back

Cheers

Robin

[MuzzerParticipant @muzzer]

Regardless of whether the label says Mutitoyo or Xmas Cracker, I habitually check the zero reading before and after critical measurements and periodically check a known reference piece. This will certainly show up any significant inconsistencies, without needing any fancy calibration equipment. My generic digital calipers seem to be pretty reliable but there again, if they hadn't been, I would have kept looking until I found some that were.

When I took one of my glass DRO scales apart to shorten it, I found nice finger prints all over it from when it was manufactured – obviously I took the opportunity to clean it, although it hadn't been causing a problem. They need to be able to tolerate a certain amount of contamination but like any tool you depend on it pays to periodically clean, check and inspect them.

Murray

[Anonymous]

Posted by Robin teslar on 13/01/2015 14:06:18:

Allow me to say, guys, that the anomalies that i observe are more like step changes say 0.15mm instead of zero. not consistent. My caliper is gerally clean, but will try some spirit. I think it has more to do with the speed at which i close to re-zero the device, maybe it cant keep up, not that i am rash of course.

A salutory observation I think. One step forward two steps back

Cheers

Robin

Which is why I almost never use vernier calipers; micrometers rule.

Andrew

[Ady1Participant @ady1]

My cheapo cross slide vernier DRO has been fine for a year or two so far, one battery change to date

Just got a 12inch one for the lathe bed, 22quid

I reckon that the location where I mount it will be the most critical factor in it's longevity and usefulness

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 13/01/2015 13:50:47:

Am I being cynical … ?

.

I neither know nor care

MichaelG.

[VicParticipant @vic]

I've got several cheap ones in the shop in case I drop them. None of them are anywhere near as good as the Mitutoyo ones that stay warm and dry in doors!

[Howard LewisParticipant @howardlewis46836]

As everyone else has said, if you have any doubts about the reading, give things a good clean.

It is surprising just how much dirt gets onto the scales and gibs!

The digital scale that is attached to the quill on the Mill/Drill occasionally produces some very interesting, but totally irrelevant readings. After a clean up, life returns to normal.

Sometimes, removing the battery for 30 seconds or so seems to return things to sanity, or to unfreeze the display.

The calliper is not good at repeatability, even with a fairly stable shop temperature, so it is worth checking/resetting Zero before almost every reading.

And, Yes, I still do use a Mic, or a mechanical Depth mic from time to time; if only to keep a check on the electronic wonders. AND they don't run out of battery at a vital moment!

Howard

[TSHParticipant @tsh73987]

I have a cheapo digital caliper (from Lidl IIRC) which in recent weeks would, without warning, change reading by 5.08mm (always this amount). This has not happened since renewing the battery.

Trevor

[Roger Provins 2Participant @rogerprovins2]

I have 5 digital calipers bought and given as presents over the years.

The best one is a "no name" that does mm, inches and fractions of inch.

It always returns to zero and is absolutely reliable on repeatability.

[martin kilroy 1Participant @martinkilroy1]

Posted by TSH on 13/01/2015 18:14:30:

I have a cheapo digital caliper (from Lidl IIRC) which in recent weeks would, without warning, change reading by 5.08mm (always this amount). This has not happened since renewing the battery.

Trevor

Two tenths of an inch

[Michael GilliganParticipant @michaelgilligan61133]

For info.

The native resolution of the Sylvac system [which is what the Chinese 'cloned' ] is in imperial measure …

MichaelG.

.

Edit: [copied from my post on a previous thread]

There is some interesting reading here

… especially the comment by Hans U. Meyer

MichaelG.

.

P.S.  You can find his Patents on espacenet

Inventor = MEYER HANS ULRICH [CH]

Edited By Michael Gilligan on 13/01/2015 20:38:42

[Neil WyattModerator @neilwyatt]

I did an experiment with my usual caliper – not Mitutoyo, it's Proops, circa 2000

Left set at 0.01 on the bench for several hours, it crept up to 0.01mm.

I then opened and closed it as fast as I could (as in literally snapping it closed). i could not get an error.

Put it on a windowsill about 5" above a heater, left it there for about two hours until it was very warm. To my surprise it read 0.10mm, quite a change!. It's back on the bench now, and in the time it's taken me to type this the display has dropped to 0.08mm.

<Interruption while one of the lads comes in and says 'have you ever heard of a band called 'Wishbone Ash'?>

It's flickering between 0.06 and 0.05mm now.

I just tested it on a 25mm test bar, and it reads 25.05mm.

My immediate conclusion is that these cheap units are highly temperature sensitive but that the error is a zero error, so that the issue is keeping them at the same temperature your zeroed them at.

Neil

P.S. it's flicking between 0.04 and 0.03 now, and doesn't feel warm anymore.

[John CParticipant @johnc47954]

And there's the rub…

[pgk pgkParticipant @pgkpgk17461]

It's only a fair test and criticism if you repeat the experiment with your mitutoyo's. Of course if they creep….

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 13/01/2015 20:36:05:

Left set at 0.01 on the bench for several hours, it crept up to 0.01mm.

.

Neil,

I'm struggling to understand that statement ^^

MichaelG.

[Author]

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