Digital calipers

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Mr Ron
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Digital calipers

Post by Mr Ron »

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? They have been around for a long time. I also include dial and vernier calipers in this question. All the precision measurement companies manufacture calipers of all forms, 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? As an amateur machinist, I only work to thousands, but I know tens of thousands and even millions is needed and used in industry. Please set me straight as to the role of the caliper in the machine shop.
Mr.Ron from South Mississippi
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WesHowe
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Re: Digital calipers

Post by WesHowe »

I use calipers all the time. But I use a micrometer on the final cut(s) when I need to be tight. My observation has been that I cannot get consistent readings consecutively with the same calipers on the same work piece. I frequently find that after measuring a larger piece, when I close the calipers I am not longer at zero. I suspect there are two issues... first, the thin design of the jaws makes a reliable, repeatable grip of round objects difficult. And second, as I understand it the electronics just count tiny marks as they pass by, and I am thinking sometimes they miss a count, because the re-zero problem I mentioned happens more often when I open and close the jaws faster.

From what I have seen, outside of the "big name" brands, there are two designs that predominate. One uses an LR44 battery, the other a CR2032. The first costs $15 or so, the other more like $35. I feel the $35 ones are better at, but do not eliminate, the issues I cited (and the battery lasts longer). I refuse to pay the $100+ price the "big names" are demanding, and thus have no experience with them. I would expect that the jaw width issue is probably the same.

With a micrometer, I can get a reading that is the same again and again on the same piece, to the tenth of a thousandth. I don't always need that kind of accuracy, but when I need a single thousandth absolutely positively, I use a micrometer. Calipers are not always that accurate in practice, even if they are in theory.
John Evans
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Re: Digital calipers

Post by John Evans »

Quick close measurements ! I have at last count about 10-12 calipers one digital for quick inch-metric conversion,the rest dial with a couple of verniers floating around. Biggest issue is the fact the sliding member has a gib which can allow a bit of rocking which affects the reading,also the users technique of use can cause errors.The best way is to use your fingers to close the jaws rather than pushing the slide. Closer than .002-3 I get out the mics. Biggest issue/mistake I see people doing is measuring a OD then trying to bore/measure a ID with the other side of the calipers and expecting to get the needed fit when done.
But allowing for all of the above I still use my calipers a LOT!! You just have to understand their limits.
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SteveM
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Re: Digital calipers

Post by SteveM »

I use John's method of closing the calipers by the jaws and get consistent measurements.

If I'm only working to a non-critical dimension, I might use the calipers for my final measure, but for anything else, I might use the calipers to get me close, but the mic to get me to finish size.

The inside measure jaws on a caliper have small flats and therefore will always give an incorrect measurement.

I have an internal mic, small hole gauges and telescoping gauges for bore measurements.

Steve
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warmstrong1955
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Re: Digital calipers

Post by warmstrong1955 »

For me, it's just depends on what I'm machining.
There's caliper work, and there's mic work.
Some things don't matter if they are a thou or two over or undersize. Some things do.

Bill
Today's solutions are tomorrow's problems.
Mr Ron
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Re: Digital calipers

Post by Mr Ron »

I understand the limitations of calipers, but why do companies like Starrett, B&S, Tesa, Mitutoyo and other big name companies make them; they are not at all cheap. In fact, they usually cost more than micrometers.
Mr.Ron from South Mississippi
John Evans
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Re: Digital calipers

Post by John Evans »

In a word Convenience ! one 6" caliper for close measurements replaces 6 mics, a set of tell gauges, a set of small hole gauges etc.
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Downwindtracker2
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Re: Digital calipers

Post by Downwindtracker2 »

At work,in a maintenance shop, they gave a quick and easy read. If you had to go to the toolroom and get the big set, change the anvil and check it, or reach over and grab the calipers then glance down at the dial, which would you choose ?

In woodworking they are great, the numbers are big, either in imperial, metric and fractional. That change by pressing a button is handy, the spindle on my lathe had an odd number, but it made sense when I switched to metric.

Unlike mics where the ratchet or thimble will give consistent reading by almost anyone, a calipers is a feel acquired by practice. If they are metric verniers, a lot.
A man of foolish pursuits, '91 BusyBee DF1224g lathe,'01 Advance RF-45 mill/drill,'68 Delta Toolmaker surface grinder,Miller250 mig,'83 8" Baldor grinder, plus sawdustmakers
SteveM
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Re: Digital calipers

Post by SteveM »

Downwindtracker2 wrote:In woodworking they are great, the numbers are big, either in imperial, metric and fractional.
I've seen the dial ones with fractional, but not digital.

Steve
Mr Ron
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Re: Digital calipers

Post by Mr Ron »

I now understand a caliper can be a convenience tool for approximate measurements, but that doesn't explain why fine tool companies make such expensive calipers when a Harbor Freight caliper can do it as accurately and at much less cost.
Mr.Ron from South Mississippi
John Evans
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Re: Digital calipers

Post by John Evans »

Mr Ron wrote:I when a Harbor Freight caliper can do it as accurately and at much less cost.
Don't count on it !! I've had a few of the low end ones and ended up giving them to people who didn't know better or much care. I have one Fowler that is not too bad ,nice feel and repeats well,but still not as nice as my B&S or Mitutoyo's .And battery life there is no comparison HF to say a Mitutoyo.
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ccfl
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Re: Digital calipers

Post by ccfl »

They make $150 calipers because, apparently, there are lots of people out there who want to buy them. I know, I don't understand those people either.
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