Best Caliper for Shop Use? Digital vs. Dial Caliper vs. Vernier-type

bobdoering

Stop X-bar/R Madness!!
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#41
Finding Measurement Pressure

The actual measurement pressure is the force applied by the pressure device minus the force necessary to move the caliper sliding jaw on the caliper beam, which can vary greatly even on two “identical” calipers.
To determine this force simply fasten the pressure device to the caliper, move the sliding jaw to touch the pressure device cylinder, zero the caliper and, by pulling the sliding jaw against the pressure device, see how far the sliding jaw is pushed back towards zero when released.
If the sliding jaw is pushed back to less than 1 mm, then the sliding jaw “friction” is less than the table value – which is good, as full cylinder movement (distance) can be used when measuring.
I am a big fan of gage R&R, because it tries to capture some of the issues that people would otherwise ignore or dismiss when picking a gage - especially as the gage resolution relates to the statistical resolution (the resolution you really get). That is not my point, however, for this discussion. The issue is gage pressure. Calipers are better than common micrometers - by the nature of their design. It is simple to show - do some gage R&R with a caliper versus a micrometer on marshmallows. It may exaggerate the case, but it illustrates it very clearly. There is another physical phenomenon that does not show up in these exercises - and is not mentioned in the above gage pressure discussion - but is the heart of further measurement variation on the shop floor - and that is impact. Since operators are generally in a hurry, they may tend to run up their gage quickly to a part for measurement, creating impact. Impact force significantly exceeds any pressure you can measure from applying the thumb to the sliding jaw. It may also create floating zeros from the zero button, also, as the operators chase this around. Impact is usually not captured on gage R&R studies because they are performed in a more relaxed environment. Any if anyone shows you how they measure something, they will not likely exhibit impact. But walk away and let them get into their rhythm, and it is there - and depending on the working conditions (pressure to get parts out), etc., it can get bad.

Something to ponder...:cool:
 
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G

Gordon Clarke

#42
OK John, I'll start off by thanking you for commenting :) and your use of colour cetainly helps.
However (here it comes), I'm not sure when you are commenting my pros and cons and when you are intending to add to the pros and cons. Is there any chance you could give me a shortened version of your actual pros and cons so I can update?

I do have some comments of my own to yours :)

Pro: They are reliable as heck and for some undefinable reason I think that the process of learning to use them has some intangible benefit for the person doing the learning.
"They are as reliable as heck ...." In my ears (remembering I'm a "foreigner") that sounds more like a "con" than a "pro". Is "heck" meant in a positive way?

Pro: Maybe I'm just too old and been at this way too long, but I just trust a high-quality make of dial caliper more than I trust a digital (partially because I've seen too much pointless and expensive scrap caused by that darn zero button).
The zero button on many calipers (nowadays) is situated in a place where, unless you have some weird hand deformation), is as good as impossible to "hit/touch" when measuring. I'd say it's a question of looking out for this when purchasing.
"Old dogs can't learn new tricks" - rubbish - I'm older than you :)

Con: Ya can't just use a dial caliper in a machine shop environment, throw it on your workbench at the end of your shift, and expect it to survive.
I'm not sure how serious you are here. Measuring equipment isn't a hammer or a screwdriver that should be "thrown" on a bench or any place else. I'm open to suggestions but I can't tink of any measuring equipment that will withstand a "throw" - and that includes a steel rule. Take care of your tools and they'll take care of you.

Having tools that can easily switch between measurement systems should be handy for anyone who, unlike myself, is not a lunatic.
My original pro for metric/inch was meant more along the lines that the same caliper could be used worldwide. I don't know if you know this, but the USA is just about the only country that only uses inches instead of metric.

Con: I must respectfully disagree with your assertion that digital is more accurate than dial (although I agree, more accurate than vernier). In my experience, it seems to depend on the level of experience on the part of the person using the tool: newbies seem to be better with digitals than dial calipers while old f*rts like me tend to show better repeatability with dial gages.
Just as many micrometers and dial indicators have gone digital (with 10 times the accuracy of the "old" types) so have calipers. At an exhibition in Stuttgart (Germany) I was at a few months ago I saw and handled a 6" digital caliper that was accurate to within 0.0001 inches.Everyone I saw measure something with it smiled and shook their heads in disbelief - including me. It was only about 3 times as expensive as a normal high quality caliper. It's specified accuracy was the same as the Sylvac Microcal which can only measure externally and only up to 4". Btw, this caliper (Sylvac) has a built-in pressure device. I don't think you tried using digital calipers for some time - am I right?

If you are measuring something that requires a degree of accuracy to where a pressure device is necessary for your caliper, in my very humble opinion you shouldn't be using a caliper in the first place.
One of the advantages of a caliper pressure device is that the user can concentrate on measuring and get full use of both hands. Another is that it eliminates too much user influence on the pressure being used. I'll bet you know some who say they don't need to use the ratchet on a micrometer and have it all "in the feel". I won't deny that's possible, but I've also seen jerks use a micrometer when they couldn't find a clamp!
Re "you shouldn't be using a caliper in the first place" my following remark is not intended to make me "Mr. Popular" in the USA. I've been to the USA several times and it's always surprised me how old fashioned and hyper modern things can be.
Sadly I think USA is losing the battle in the manufacturing world - and not just because of high wages and standard of living. I share the American love for "gadgets" but in some fields there is a tendency to "stick with what you know". They can be found in the USA but almost everyt small machine shop in Denmark (and most of Europe) looks like something you'd expect to see at NASA :) If you Google on facts for Denmark I think you'll find it's one of the top five countries in the world as regards standard of living.











 
G

Gordon Clarke

#43
Bob, I don't need to ponder :) you have much the same experiences as I do. If you want, what I'd consider, the latest R&R on calipers (and especially on caliper measurement pressure) then I can send a link on a PM to you. I'll bet I can surprise you with the latest developments within the last 6 months.
Look at how fast computers are developing - Megabyte, Gegabyte and now Tetrabyte. The mind boggles :D
 
J

John Nabors - 2009

#44
OK John, I'll start off by thanking you for commenting :) and your use of colour cetainly helps.
However (here it comes), I'm not sure when you are commenting my pros and cons and when you are intending to add to the pros and cons. Is there any chance you could give me a shortened version of your actual pros and cons so I can update?

I do have some comments of my own to yours :)

Pro: They are reliable as heck and for some undefinable reason I think that the process of learning to use them has some intangible benefit for the person doing the learning.
"They are as reliable as heck ...." In my ears (remembering I'm a "foreigner") that sounds more like a "con" than a "pro". Is "heck" meant in a positive way?

Pro: Maybe I'm just too old and been at this way too long, but I just trust a high-quality make of dial caliper more than I trust a digital (partially because I've seen too much pointless and expensive scrap caused by that darn zero button).
The zero button on many calipers (nowadays) is situated in a place where, unless you have some weird hand deformation), is as good as impossible to "hit/touch" when measuring. I'd say it's a question of looking out for this when purchasing.
"Old dogs can't learn new tricks" - rubbish - I'm older than you :)

Con: Ya can't just use a dial caliper in a machine shop environment, throw it on your workbench at the end of your shift, and expect it to survive.
I'm not sure how serious you are here. Measuring equipment isn't a hammer or a screwdriver that should be "thrown" on a bench or any place else. I'm open to suggestions but I can't tink of any measuring equipment that will withstand a "throw" - and that includes a steel rule. Take care of your tools and they'll take care of you.

Having tools that can easily switch between measurement systems should be handy for anyone who, unlike myself, is not a lunatic.
My original pro for metric/inch was meant more along the lines that the same caliper could be used worldwide. I don't know if you know this, but the USA is just about the only country that only uses inches instead of metric.

Con: I must respectfully disagree with your assertion that digital is more accurate than dial (although I agree, more accurate than vernier). In my experience, it seems to depend on the level of experience on the part of the person using the tool: newbies seem to be better with digitals than dial calipers while old f*rts like me tend to show better repeatability with dial gages.
Just as many micrometers and dial indicators have gone digital (with 10 times the accuracy of the "old" types) so have calipers. At an exhibition in Stuttgart (Germany) I was at a few months ago I saw and handled a 6" digital caliper that was accurate to within 0.0001 inches.Everyone I saw measure something with it smiled and shook their heads in disbelief - including me. It was only about 3 times as expensive as a normal high quality caliper. It's specified accuracy was the same as the Sylvac Microcal which can only measure externally and only up to 4". Btw, this caliper (Sylvac) has a built-in pressure device. I don't think you tried using digital calipers for some time - am I right?

If you are measuring something that requires a degree of accuracy to where a pressure device is necessary for your caliper, in my very humble opinion you shouldn't be using a caliper in the first place.
One of the advantages of a caliper pressure device is that the user can concentrate on measuring and get full use of both hands. Another is that it eliminates too much user influence on the pressure being used. I'll bet you know some who say they don't need to use the ratchet on a micrometer and have it all "in the feel". I won't deny that's possible, but I've also seen jerks use a micrometer when they couldn't find a clamp!
Re "you shouldn't be using a caliper in the first place" my following remark is not intended to make me "Mr. Popular" in the USA. I've been to the USA several times and it's always surprised me how old fashioned and hyper modern things can be.
Sadly I think USA is losing the battle in the manufacturing world - and not just because of high wages and standard of living. I share the American love for "gadgets" but in some fields there is a tendency to "stick with what you know". They can be found in the USA but almost everyt small machine shop in Denmark (and most of Europe) looks like something you'd expect to see at NASA :) If you Google on facts for Denmark I think you'll find it's one of the top five countries in the world as regards standard of living.
Gordon-

I guess I'm guilty of being your typical 'Ugly American' and of assuming that everyone in the world understands my US colloquialisms. I plead guilty and am ready to face my punishment :bigwave: Hopefully this will only involve being beaten with al dente pasta.

I don't have time to address all your points but I will hit a few and get to the rest as soon as I can:

1) Yes, 'reliable as heck' is meant in a positive way.

2) The 6" Mitutoyo digital caliper I currently have has a zero button in a very inconvenient location, and causes me to use some very unfortunate language when I am trying to get a measurement in an awkward angle. As for this:
"Old dogs can't learn new tricks" - rubbish - I'm older than you :)
Just because you are older than me doesn't mean that your mind isn't more nimble than mine!!

3) Yes, I am quite aware that we in the US are the only barbarians left in the world not using the metric system and I believe this is harming our competitiveness. One of the questions in the "New Folks.." thread is, "If you could change one thing.." It's hard to pick just one thing I would change about the quality field, but one might be to drag the US, kicking and screaming, into adapting the metric system. It makes so much more sense and I for one am quite comfortable working in it.

4) Please PM me with information about the 6" digital caliper with .0001" accuracy. I WANT ONE!!!!:)

5) Yup, Denmark is one of the top 5 countries in the world in terms of standard of living, and sadly, the US is not (but we are in the top 15!!).

Kind Regards -John
 
Last edited by a moderator:
G

Gordon Clarke

#45
Good Lord John, a guy with the same warped sense of humour as myself :D We don't make life easier but we do have fun at living it.
I think I wrote a bit more diplomatically than your reply in no. 3) indicates :)
When I left Scotland to live and work in Denmark, Britain at that time still used the inch system (Imperial System). It took me about a couple of days to get used to the metric system - I'd hate to think how long it would have taken me if it had been the other way around.
If I can't figure out how to PM you, I'll get back to you.
 
G

Gordon Clarke

#48
A little something on digital caliper accuracy.
For those that buy electrical equipment and wait till the xxxx hits the fan before reading the instructons, save yourself time and stop reading now :D
To the others, my advice is:
When you get a new digital caliper clean it and insert the battery (if it's not already in place).
Zero the caliper and find something where you know the exact diameter or length i.e. a plug gauge or gauge block. What does your caliper read? if it's off by more than the specified acuracy in DIN862 (or similar) then return it!
I've written caliper length specifications (DIN862) earlier in this thread. There is of course much more than just that in them.
The biggest problem for a digital caliper (in fact all calipers) are measurement of small holes. Try with a small hole ring gauge i.e. about 1/4" or so. Again, if it's (the caliper) not within spec. return it!
Does anyone know a happy man (or woman) who bought a new car without a test drive? If your caliper is off the exact measurement then you'll know how much to compensate by, as any deviance usually (not always) applies to the whole length. If a digital caliper (up to 40") is used for comparison measurement and zeroed on for example, a gauge block the same size as that about to be measured, then the caliper accuracy should be within 0.0005"
Now I'm wondering if any caliper manufacturer will say I'm misinforming :) If not then please tell folks I'm right.
To quote my dad, "I'm not always right, but I'm NEVER wrong" :D
 
G

Gordon Clarke

#49
This is a quote from, and my reply to, an earlier posting in this thread.

If you are measuring something that requires a degree of accuracy to where a pressure device is necessary for your caliper, in my very humble opinion you shouldn't be using a caliper in the first place.
One of the advantages of a caliper pressure device is that the user can concentrate on measuring and get full use of both hands. Another is that it eliminates too much user influence on the pressure being used. I'll bet you know some who say they don't need to use the ratchet on a micrometer and have it all "in the feel". I won't deny that's possible, but I've also seen jerks use a micrometer when they couldn't find a clamp!

Now to my reason for mentioning it again:

I've always maintained that no "officially" recommended measurement has ever been made for caliper measurement. Anyone that has ever used a (digital) caliper with extra long legs knows how sensitive the result is to too much pressure!
Has anyone ever seen recommended caliper use measurement pressure?
In every standard I have seen, there is a "vague" remark about applying a suitable pressure - whatever that means :) It sounds like a Catch 54 arguement. Equally similar is "never drive faster than road conditions permit" - which, to me, is like knowing in advance that an accident is about to happen.
 
G

Gordon Clarke

#50
I forgot the word "pressure" in my last posting - which makes it a wee bit confusing :)

I've always maintained that no "officially" recommended measurement pressure has ever been made for caliper measurement. Anyone that has ever used a (digital) caliper with extra long legs knows how sensitive the result is to too much pressure!
 
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