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Digital Calipers
2

Digital Calipers

Digital Calipers

(OP)
Can anyone recommend a model of digital calipers?  Accuracy requried is 0.0005".  I am finding online information is confusing resolution with accuracy and want to make sure I get the right tool the first time.

Thanks a million,
Rebecca

RE: Digital Calipers

By a vernier and no one will ever steal it.  You will have accuracy to .0001"

RE: Digital Calipers

Buy the 8-inch (at least).  I get a chuckle every time my neighbors are stymied by something that is 6.1" long.

RE: Digital Calipers

flyfunky
Most of the big manufacturers produce decent digital calipers starting at around $100 and very rapidly escalating from there. You have to ask yourself what features you need, or do not need, and price accordingly.
 Having acquired one,hide it, in the back of your box.
Then go to Harbor Freight and buy a $24.99 stainless digital caliper It's good to plus or minus 0.001" and give this to the scroungers who want to borrow your digital caliper. Whatever you do, do not, lend your good one out.
B.E.  

RE: Digital Calipers

(OP)
Thanks for the valuable information.  I will be ordering the Mitutoyo as above.  

Berkshire - They will be kept well out of site and I will be only lending out the old Kincrome set haha

Thanks again for your responses smile

RE: Digital Calipers

TheTick,
This is not the joke thread, and they didn't get it.

RE: Digital Calipers

If you actually _use_ the caliper, you will not be impressed with the battery life, no matter the brand.  Battery life is further shortened, dramatically, if you have and use a data interface.

Note that you also have to pay extra, a lot, for a digital caliper that is water resistant, and less likely to lose its mind for a while after being sprayed with water- based coolant (which typically has wetting agents in it).

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Digital Calipers

(OP)
TheTick

I did get a giggle thanks smile

RE: Digital Calipers

" By a vernier and no one will ever steal it.  You will have accuracy to .0001 "

....where do you buy a VERNIER that's good for tenths ?

 

RE: Digital Calipers

Beware!!! you WILL break the thumb wheel off that caliper unless you really take care of it.. We have a whole bunch of those here all with broken thumb wheels.. Sometimes the crack takes out the battery compartment too.
We get battery life of about 1-1.5 years with that model. Great caliper though as long as you respect the plastic/thumbwheel.

RE: Digital Calipers

Vernier to .001"?  Had to dig in my memory a little deeper.  When I was a young machinist, I used a vernier that went to .0005", and the micrometer (precision C-clamp!) went to .0001".

All the precision in the world doesn't help if you don't learn to hold the thing right.

RE: Digital Calipers

   Are we talking calipers here, or micrometers?

   Micrometers, digital or vernier, are good for .0001".  I regard calipers as good for .001".  The digital readout might indicate .0005", but you should try it out on gauge blocks.

   I strongly agree with TheTick about vernier tools.  Nobody borrows mine.  When I need them, they are in my desk drawer where they belong.   

               JHG

RE: Digital Calipers

williedowg,
You buy the vernier caliper and a BIG magnifying glass.
B.E.

RE: Digital Calipers

Never trust a caliper, whether it's vernier, dial, or digital, to anything closer than 0.003.  Of course you can read the graduations to a thou or 5/tenths, it doesn't mean the accuracy is there.  You're only fooling yourself.  Get a mic if you need to be closer.  I started in the machine shop in 1982 and have used nearly every measuring device that is available to a machinist or toolmaker, and a caliper simply cannot be trusted that close.  Browne & Sharpe is the hands down winner in a dial caliper, followed by Mauser.  Wouldn't waste the money on a digital.

RE: Digital Calipers

Etalon makes a very good dial caliper as well.  Don't know if the Mauser is even being made any longer.

RE: Digital Calipers

A digital caliper is awfully convenient to use. I think it also helps measurement accuracy by being able to read while taking the measurement. It allows you to manipulate the calipers to get the smallest reading which means that you are square to the object. And you don't need to be a contortionist as often to read the display accurately.

But, I have seen mechanics accidentally hit the hold button without realizing and take bad readings. Dead batteries is a pain. Dial caliper are almost as convenient as digital and no batteries.

RE: Digital Calipers

You can trust a caliper about as far as your measuring skills and habits.
  • Clean oil and grit before measuring
  • Hold caliper squarely
  • Apply the right touch: enough for solid contact, not enough to deform part
  • Check zero before measuring
  • A good measurement is one that can be repeated
  • Repeatable measurements are good
  • It never hurts to cross-check against another instrument
  • The CMM is probably wrong
  • It takes a special touch to measure hole diameters.  Really small holes may be off due to thickness of tines

RE: Digital Calipers

I have a Mitutoyo vernier, a Mitutoyo dial and a Starrett dial.  All are 6-inch calipers and very close to each other on gage blocks, with the vernier taking the lead.

Most of my measurements do not require such precision, but I use them anyway and then convert to the required accuracy. In my business, it's like measuring with a micrometer, marking with a crayon, and cutting with an axe.

RE: Digital Calipers

I made the mistake of getting a solar powered caliper. I found it difficult to get measurements on dark areas of machinery, and ended up bringing a flashlight with me on service calls.

Russell Giuliano
 

RE: Digital Calipers

Hi Tick, always good to banter with a fellow machinist.  Your part about cross checking with another instrument (better yet a gage block) is good advice.  I do have to take to issue the repeatable measurements.  I have a drawer full of cheap calipers that are basically bait for the "tool borrowers" in our company, that will repeat the measurement to within a thou all day long, but it's still the wrong measurement! You can adjust to zero, but unless you wring up a stack of jo blocks that are very close to your target measurement, it ain't gonna do it! By the time you've gone to all that trouble, you could have either set up a snap gauge or just gone with a mic.

All calipers, even the Swiss ones, have an inherent parallax error because the jaw needs to slide.  They contain backlash and tensioning mechanisms and all of that, but I have found that to be safe, you just can't trust them to anything finer than about 3/1000.  My Browne & Sharpe and Etalon are both trustable to about a thou, but no human hands other than mine have ever touched them. (well, that are still living, anyway, LOL)

My funniest experience is when I witnessed a mechanic taking cylinder bore readings on an engine block with a dial calipers.  Yes, a standard 6 inch dial caliper!  I think the look on my face must have sent a chill down his spine because he immediately asked if there were a more accurate way of measuring.  He now owns a nice set of telescoping gauges and the mics to go with them.

RE: Digital Calipers

0.0005"? That's around 0.01 mm.
Please check the datasheets for digital calipers, and you'll not find a manufacturer that specifies better tolerance than 0.03 mm.
That the readout shows you 0.01 mm is a different matter.

Benta.

RE: Digital Calipers

True, repeating doesn't guaranty accuracy.  It does at least verify technique.

At my last machining job before graduating and moving into engineering, I had to watch the inspectors.  They were so sloppy that good parts would get rejected just because they couldn't hold caliper properly.  My "rework" consisted of a demonstration and lesson.

RE: Digital Calipers

The Tick,
 It never changes does it? I have a friend who is a corrective action engineer for a well known aircraft company. This week that person had to deal with a bunch of rejected "good" parts because the bores had been measured with a digital caliper instead of a 3 point micrometer.
  When they were measured with the right equipment, they were well within tolerance.
B.E.

RE: Digital Calipers

In my days on the shop floor a vernier (digital calliper) was always referred to as a very near. It will never be as accurate as a mic, slip gauges etc but it is much easier to carry around one 0-8" vernier than eight micrometers.

It all depends on how accurately you need to measure something but it is certainly a quick and easy way of getting a very near measurement, even if that is to find out if a piece around 5" needs a 4-5" mic or a 5-6" mic to measure it accurately.
 

RE: Digital Calipers

I don't know about you but I always used the universal measuring device, the 6" machinist rule. For really big  jobs the 18".

That aside today's machining methods have outpaced the ability to use simple and inexpensive measuring instruments on the shop floor. One thing we used for any run of parts requiring precision measurements, little tenths' we would always try to set up a comparison gauging process in lieu of a direct measurement.

I was most fortunate in about my 5th year of employment I got to attend a ten day metrology course. 5 days with an in house instructor, 5 days with outside instruction covering some theory, and new instruments and methods. I would strongly recommend that if a course, seminar, or even a demonstration dealing with metrology comes along take it.  
Again I was quite fortunate in that the company readily provided the instruments required for very accurate measurements and a relative clean room for calibration.

A bit of information gleaned from that course that has stuck with me all these years is that there are 21 geometric shapes when using a two point measurement you can get the same dimension.
I also have around 30 spring calipers of all persuasion used by my father, grandfather, and uncle for precision machining, actually comparison.
   

RE: Digital Calipers

unclesyd,

   I took Metrology in college.  It has proved useful.

   I keep a metric/English tape measure in my briefcase.  I keep losing my 6" pocket scales, but I have one at the moment.  The 6" vernier, my 0-1" micrometer (with vernier scale) and my 0-25mm micrometer (also with vernier) live in my desk drawer.  Since they are vernier rather than digital, they are in my drawer.  Perhaps some of you work in places where people put stuff back when they are finished with them.   

               JHG

RE: Digital Calipers

I forgot to add that the only geometric shape you can measure with a fair degree of accuracy with  a 2 point gauge is a sphere.  
In my previous post the 21 geometric shapes pertain to bores.

[b]drawoh/b],
Our two big shops used the brass token approach to getting anything checked out of tool crib back. As far as scales go I usually could sneak in an order for dozen at a time. I was real bad about cutting them down to rough align a Faulk coupling.

It just dawned on me that years ago when a new batch of machinists in training were given there first it would be to make a C Clap with a 1" throat.  I guess that was to replace the 1" micrometer.
 

RE: Digital Calipers

I used to have a nice 8" steel rule that I did carry almost everywhere and even got callibrated yearly.  However, that vanished at some point and I never got round to replacing it.  I have a cheap set of 6" digital callipers that are mine, and I have a slightly better work pair (shared in my dept, which is now just me and a colleague and he I think has his own, so they're basically mine).  However, I don't routinely carry them with me like I did my rule.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Digital Calipers

Not to be the wet blanket... but I will.

Given todays competitive environment, should you be loaning out poor measurement tools to people in your own company?

RE: Digital Calipers

The accuracy in any measurement lies in the proper training and use of the metering device. Also; accuracy, repeatability and reliability lies in the requisite regular testing and calibration of the instruments in use.

Check the ISO 9000 std.  

RE: Digital Calipers

ISTR that if you work for an ISO company, you should leave your own measuring tools at home, and use the controlled and calibrated ones provided by the company.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Digital Calipers

The ISO companies I worked for paid to calibrate personal instruments at work.  On calibration day, bring every caliper, rule, and tape measure you own!

RE: Digital Calipers

Speaking of measuring I just got a call asking where i bought some Hastelloy C Cylinders (5" dia x 24" lg with 1.0625 wall) I purchased in he early 80's and the company is no long in business.
It seems that someone just cut them down to a new length, the only problem being they are now 1" too short.
Supposedly this was a digital readout that was in error.

TheTick,
I have a ten foot tape measure that is all white no numbers, how would it fit in the calibration scheme.  

RE: Digital Calipers

Simple, syd, I'd calibrate to measure 10 feet plus or minus 10 feet.

Better, a sticker we once put on a broken pressure gage said "calibrated to measure: nothing, +/- infinity".

RE: Digital Calipers

As a slight diversion, never underestimate the usefulness of cheap measuring devices. Some very large firms which I have worked for (design and stress depts) won't provide a measuring device unless it's properly calibrated - these cost money, therefore they don't have anything and trying to weigh something has to be done with a job number somewhere off site.

This is all fair enough unless you just want to know the weight of a 125g object +/- 5g, in less than 2 weeks! I just brought my digital kitchen scales in and calibrated them myself with an old 1lb stamped weight. What do you know, the $20 scales were there within 2g!

Metal verniers for me every time and yes I do keep them near all the time and was trained how to use them.

A slightly inaccurate answer is often 1000% better than no answer at all.

RE: Digital Calipers

By 'stamped' I mean that the lead plug in the weight had a customs and excise seal imprint.
 

RE: Digital Calipers

unclesyd,

   I built a shed in my backyward last fall.  I had problems with my tape measure which measures inches, feet and inches and millimeters.  The feet and inches text is on the opposite side of the tick from the inch dimension, which caused me to measure a half in inch off, repeatedly.

   And I was unable to find my lumber stretcher.

   If I were serious about framing, I would get a tape measure calibrated only in feet and inches.  

               JHG

RE: Digital Calipers

Your not the first or the last. One of the better carpenters I know had the same thing happen to him last year and the biggest problem it was on a job with a lot of onlookers.

I had a lot of fun with the blank tape on the job as every time a fitter would miss a measurement I would hand him the tape and grease pencil and tell him just to make one mark.  

RE: Digital Calipers

Greg:

So, be honest, who carries an appropriate measuring instrument with them most of the time?

Is that the real sign of being a crusty?

...---...---

I keep a (plastic) mm+in caliper in my cell phone holder with my LED flashlight for rough measurements, plus a 16 ft inch+mm tape measure on my belt.   Sure, neither is calibrated, but when I need to confirm a bolt diameter, or explain to a Spanish worker overseas how long to make the scaffolding under the genrator, I don't need/want thousandths tolerances.   In the tool room, there are calibrated devices, I want the millwrights to use them when appropriate, but my own are needed where I am, not back down a dozen ladders and across the road in the turbine building.

Sure, you can make inches and mm errors, but I NEVER want to make conversions in the field.   So I always carry double reading tapes and rulers.

Also, in today's non-tech, poorly trained worker, never shop-disciplined and poorly union-trained as youngsters and helpers, I will not trust most vernier readings, but feel they are more likely to make less errors with a digital instrument.   Sure, the "old guys" will read verniers correctly.  But the youngsters can't nowdays.   

In today's work, would I trust    

RE: Digital Calipers

I have a mitutoyo 0-12 inch vernier.

factory QC test shows its accuracy is  +-.001' from 1-6' and .002 from 6-12, mostly stainless, except for the casing around the dial which is plastic, but only a cover, the housing with the gears is contained in stainless as well, so the plastic cover is more for style.


@racookpe: 32 is a youngster to someone who is 65, and it doesnt take a genius to use a vernier, dont squeeze hard, and find hold it square.

but as for the topic of the thread, if you need accuracy to tenths you can not use ANY vernier, not even brand new.
use a micrometer.

like that guy said vernier = very near.


just use a micrometer.
if its a small part, and you're pressed for cash, check this out

http://www.instructables.com/id/DIY-Digital-Caliper-Micrometer-Comparator/

RE: Digital Calipers

Let us remember that vernier and caliper are two different things. Vernier scales are used on micrometers as well.

RE: Digital Calipers

There are a lot of people that seem to be claiming poor accuracies with verniers.  I have a pair of Mitutoyo 8" verniers and have no problems measuring gage blocks and the like to the nearest 0.001 (the read out gives to the 0.0005).  Given odd shapes or spheroids the measurement becomes a bit rougher, but you can certainly obtain accuracies in the thousandth range by careful measurement of a clean surface.

As far as batteries go, they last forever.  I think Mitutoyo says the batteries are good for 3 years of use.  I know mine have gone over a year of frequent use with no change of batteries.

The claim that the wheels break and things like that strikes me as odd.  Calipers are an engineering tool, so treat them as such and they will last forever.  If you treat them like a common tool (think hammer) they wont last you as long as you would hope.

Get a good pair, and learn how to use them.

RE: Digital Calipers

10 different people will get 10 different readings using digital calipers. If you need to maintain that accuracy you would need a micrometer.  

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