Digital calipers

[BadDog]

I think it's clearly about appropriate quality. Good name non-cheap calipers are not micrometers, but they are still reliable and consistent within their state limits. And if used properly you can expect it to read roughly the same at any point on the caliper. Cheap might be 0.002 under below 2", and then drive 0.002 over by 4", or anything in between. Each one can be expected to range differently. I grab a mic, good 12" Mitutoyo digi-calipers, cheap HF, B&S Vernier 14", a scale, or a tape as I think appropriate to the application, and what I feel is suitably convenient. I trust my Mits or B&S to final machine tolerances much closer than the HF, and don't have to fiddle with a mic. So they sit squarely between my HF calipers (used for fab work and stock/saw size check mainly) and my micrometers. If all I had was a cheap set of calipers, I would feel obliged to grab the mic and fiddle with that when as it is, I do not. If all I had were HF calipers and good micrometers, my tasks would get substantially more frustrating due to using the micrometer much more than I have to with the Mits and B&S at hand...

[Downwindtracker2]

I use a electronic calipers, they are deluxe inexpensive ones. But they never truly shut off, so it seems every time I use them I have to change the battery. I've gotten to leaving a card of batteries on their case. Watch a couple of YouTube https://www.youtube.com/watch?v=KnDype-j3hk

and https://www.youtube.xxxxxxxxxxxx This give you idea.

Second link removed, as it was a duplicate of the first link.
H

[pete]

A tough question to give a definitive answer to Ron.I guess it all depends on the person and what there shop is mainly for as to how useful, accurate and valuable a set of calipers really are to them. I could I guess get by without having a decent set of calipers but sure wouldn't want to. Everything there used for would take a bit longer and be a bit more of a pita just like Russ said. Besides the more normal shop measurements I've used them over the maybe more traditional ways for setting table saw cuts, router work, home renos, even some plumbing. So I know I'd really hate to be without mine. John, Steve and maybe a few others mentioned closing the calipers by using your fingers. Maybe 8-10 years ago I ran across a Mitutoyo video showing how to properly measure with a set of calipers and they weren't using that thumbwheel. That's for quickly moving fairly large distances. They showed closing the caliper jaw by using your fingers and thumb to lightly squeeze the caliper closed. Or with larger calipers and parts using both hands to hold the fixed jaw in place and close the other jaw. That still takes a consistant light practiced touch, but after trying it on stacks of unknown size gauge blocks I do think it gives consistantly better and possibly slightly more accurate results. And I think the more use a set of calipers has had the more important it is to measure that way. They can wear slightly and the movable jaw can then move slightly out of square with the fixed jaw during a measurement if your not careful. Unfortunately I've never been able to refind that video, maybe it's no longer on there website. "Do we really need them?" Any question raised about what calipers to buy over on the Practical Machinist forums gets most of those pros saying there using there calipers all day every day. So it seems lots of shops including CNC are using them even in commercial situations. I've checked myself enough times I'm pretty confident I could get repeatable measurements within .002" to maybe a tiny bit less if I take more time and double check the measurement a few times just to be 100% sure. But if I have to have it closer than .005" or less then it's probably faster and easier to just use a micrometer to be dead sure and quit wasting more time while still not being totaly confident of the caliper measurements. Almost never will I use the inside jaws since the smaller the hole the more inaccurate they are.

Apparently there are at least one or two digital calipers made in Europe? that will read to and are supposed to be accurate to a couple of 10ths accuracy. The one price I saw mentioned was about 5k some years ago. Why there made I don't know. I'd still trust a good micrometer over any caliper no matter how well made and costly. But again I think it also depends on just what main use your shop and tools are for. If you do mostly fab and welding then probably any caliper, a decent 12" combination square, carpenters square and good tape measure would be good enough. And if that's all I was doing I'd be buying the cheap calipers since it's likely any set would see a short life in a fab shop. For me calipers would be the most used tool whenever I'm in my shop most times so I bought the best I could afford and a second mid range set for any rough work. But from what I've read for the best repeatable accuracy with any calipers then a good brand name set of vernier calipers with an experienced person using them are still supposed to be a bit more accurate than the dial and digitals. I'd be dead slow using them and for sure I'd need better eye glasses than I have right now and almost for sure be more inaccurate.

Before the modern type of vernier calipers were invented they did some very precision fits using the old school inside and outside calipers that couldn't really measure anything on there own.They had to be preset or set to the part size then check that against a well made and trusted scale plus a a good calibrated feel and a very well adjusted mark I eyeball. The same could still be done today if we really had to for what a lot of what were doing maybe. I doubt I could do it without a whole lot of practice first. If I had to start my shop again from nothing for some reason then the very first shop tool I'd buy would be a good set of digital calipers.

[ALCOSTEAM]

The junkiest electronic digital calipers and mic that I have ever bought were Starrett. While I did not buy them brand new they were less than a year old and I doubt the original owner used them more than a few times. I kept them in their cases and in the tool box safe and sound and only used them occasionally. After maybe 2 years of ownership I went to use the 0-1 mic and it was dead so I put in a new battery, still dead. So I grabbed the caliper and it was dead so I put a new battery in it, still dead. Seems thru those years Starrett had horrible troubles with their digital stuff. I looked into sending them in for repair and found Starrett all but unwilling to mess with them as they were not repairing what was sent in but offering a bit of credit towards buying new. I told them I would take the hammer to them and never buy Starrett electronic anything again.

For just regular work I have went to using just about all HF digital calipers, for work where I don't need a mic but want really good numbers I have some Mitutoyo 6" calipers. I find them to be about the most accurate digitals I have used but they seem to eat batteries. Every pair of the Mitutoyo's I have found at the pawn shop and have not paid over about 25-30 bucks.

I still find especially when doing roughing work I like regular dial calipers as I can instantly look at the dial and see I have XXX to go. the same can be done with a digital by zeroing out on your finish dimension but I just like to look at the dial.

For bigger work years ago I bought a set of 24" Fowler vernier calipers. They take a bit of getting used to but are actually quite accurate. I just recently machined a 60kw generator end to match up to the bell housing on the back of a diesel engine. Since I needed to also make a bolt pattern on the part and once I got to machining I would loose my original indicating points I decided to do all the work on my 20" rotary table on the mill which the part just barely fit onto the rotary table. This was certainly a make no mistake on part. The Fowler verniers worked flawlessly and the end result when I went to test fit the locating step had to be tapped lightly to just fit into its spot on the bell housing and all 12 bolts went in perfectly.

[BadDog]

Good point. Most everyone I've talked that has or used them hates the Starrett digi-calipers. And I tend to avoid the dials for use near machines due to the problem with chips or any kind of debris making them unreliable. So my only set of dials set under my granite plate, Mits digital near lathe/mill, and HF verier near fab table. The big B&S sets in a tool drawer until needed once every few years.

[Mr Ron]

Thank you all. I have a better understanding now to the pros and cons of digital calipers. One thing I would like to add is; when taking multiple measurements over a large range of diameters or steps, with a micrometer, you have to screw/unscrew the thimble many turns, while with a caliper, size adjustment is quick. I guess there really is a need for both instruments.

[Harold_V]

Thank you all. I have a better understanding now to the pros and cons of digital calipers. One thing I would like to add is; when taking multiple measurements over a large range of diameters or steps, with a micrometer, you have to screw/unscrew the thimble many turns, while with a caliper, size adjustment is quick. I guess there really is a need for both instruments.

And Pi tapes, too. All depends on the circumstances at hand.
If you haven't used large diameter micrometers, you may not understand that they become rather cumbersome, difficult to use. Feel gets lost pretty easily, as it's easy to get misaligned. A ratchet, in such circumstances, is rendered virtually useless. In such an instance, a Pi tape can serve quite nicely.

H

[spro]

Harold. "Pi tape" sounds interesting in itself. I could search it but the use could not be as well explained as you can.

[SteveM]

when a Harbor Freight caliper can do it as accurately and at much less cost.

I have a Mitutoyo and a Horror Freight.

When the Mitu doesn't zero when I close it (it's typically off half a thou), I wipe the jaws, close it and it zeroes.

The HF fails to go back to zero by large amounts and at random intervals, so you HAVE to close it EVERY time to be sure your measurement is good.

Was going to use the HF as a quill readout, but no.

Steve

[Rich_Carlstedt]

I have heard Harold tell us that digital calipers cannot be relied on to give precise measurements and that the micrometer has to be the go to tool. If that is the case, what, then is the function of the digital caliper? Do we really need them? ..................................................... I also include dial and vernier calipers in this question....................................................... so they can't all be bad. As far as I am aware, calipers can only read in thousands, while micrometers can read in ten thousands. .......Is that the reason for dismissing calipers?........................Please set me straight as to the role of the caliper in the machine shop.

This is like a Chevy versus Ford Argument !
It mostly has to do with the way you were trained.....or were prejudicially instructed. You have to evaluate the function and the methods used as well as the tools at hand. There are those who say that digital calipers are not accurate...yet they may have magnetic scales on their lathe and mill ! Hey, in one voice they say no to digitals for accuracy, and the next minute they swear that thier DRO is good to .0002 !

See what I mean ?

When you use a Micrometer, do you also use it as a "C" clamp ? Probably not as most know , or seem to know that to do so is a NO-NO
For 40 years I have had a crusade at work teaching journeyman machinists how to use a caliper ..ALLL the caliper brochures and instructions are wrong and even the photos are incorrect . Check out this photo

http://www.mitutoyo.com/wp-content/uplo ... alLite.pdf

And that is from a very fine company. No wonder calipers have a bad reputation from some ......experts !
Guess what happens when you have loose gibs on your mill, and a DRO ? is it really responsive for accuracy ? No, it's not !

As mentioned by another poster, it is imperative to have the gibs adjusted right AND putting the measuring force at the point of contact means you never use the thumb wheel, you use your thumb and finger on the jaws exactly at the same point of contact with the work piece. Anything else is futile . Unlike mikes, your zero location can be lost, so each use requires a feel on the jaws when closed and a re-zero on the scales . While you are at it, how many times have you seen a 3 inch mike be checked with a standard, but never a caliper doing the same ? Again fellows its a whole different world to learning to use a caliper properly because of all the error in use out their
I laugh when I hear of folks trying to use a HF caliper and expect to read to any level of accuracy...It will not happen !
Precision ground surfaces and correct jibs as well as a precise micro magnetic strip is required.
Like anything, you get what you pay for. 30 years ago, I bought a Starrett Digital caliper ( 720 ) and it cost over $ 200 back then, but it reads in tenths. I could consistently match my machinists dimensions as we built dies and I walked around the shop and was asked to check on some work. Did I always believe a dimension ? NO, absolutely not. When you do critical work, NEVER believe one measuring instrument ! !
I posted pictures some time ago , but Photobucket has killed that off, but I did show the approach to using a caliper and what it can accomplish.
So what is gained by a good digital caliper and proper technique ?
1 Accurate dimensions
2. Versatility
3. Weight-compare it to a 5-6 mike
4. Absolutely fantastic when making multiples of the same Item and using a "Zero" on your desired dim, so you get a immediate + or - report
5, Reduction of math errors

What do you get with cheap calipers or poor techniques
1. Absolutely nothing

I am not trying to be argumentative fellows, but when something is not working to expectations, it's time to sit back and rethink the problem and the causes and effects. I an sure you will be enlightened with the results --whatever the problem

Rich

Side note: The early Starrett's had poor battery life ( and some others too)
This is fixed with a simple modification. My battery's last for several years .
its in one of my earlier posts

Did find these , but not he fix
http://www.chaski.org/homemachinist/vie ... r&start=12
and
http://www.chaski.org/homemachinist/vie ... per#p52280

[AllenH59]

I am going to measure my ID side of my calipers to see how they are. I am a dinosaur, and use telescoping gauges for ID fits.

[pete]

So do I Allen. Likely you already know but others may not. The reason the ID side is inaccurate is the tiny flat that's on the measuring face of each ID jaw. So the tighter the radius (smaller hole) the more they span across that radius and can't measure the actual hole diameter. If the jaws were knife sharp they could. But the edges of the jaws would then quickly wear and you'd be right back to being inaccurate again.In a home shop and for holes large enough to use them I doubt there's anything cheaper or more accurate for the money than a good set of telescoping gauges. They can't really tell you the holes slightly tapered or out of round. But that takes some large coin for proper hole gauges.