Digital vs Dial Caliper Comparison

N

notadog

A co-worker has just brought me a new 6" Dial Caliper, 0.001" resolution. We have been using 6" Digital Calipers, 0.0005" resolution.

:argue: He said he wanted to use the new ones because he felt that they were easier for him to "read". I on the other hand feel like he's not on the right track. We have both inch and metric tolerances on our drawings. He will now either have to have a metric caliper or do calculator conversions. Or use the digital ones for metric measurements.

So, I would like to know what is out there, Statistical wise (excel spreadsheet preferably), that can be used to prove this? And the instructions to perform this. Is there any other info out there that can be used to help him or I see that it does(n't) matter.

Any help on this matter would be greatly appreciated!
 

Stijloor

Leader
Super Moderator
Have you ever performed a Measurement Systems Analysis (MSA) study with these devices?
 
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I think it is easier to misread a dial caliper, especially when a persons eyes get older. I do think both the calipers you have there could be read to the same resolution by a good operator with great eyes, so that isn't a problem, (the digital one really only reads to the nearest half tenth, it is not actually reading to 4 decimal places), so you can actually interpolate less with it than the dial.
Due to the possibility of misreading however, I frown on using them here, why introduce a source of error?
As you point out, metric is just a button push away with the digital one, conversion just introduces even more error sources.
 
N

notadog

No, I haven't. I was hoping the someone had a good example that could be presented to him and his supervisor. A non Biased approach.
 

Ninja

Looking for Reality
Trusted Information Resource
Without data from your side (with that person) showing that his readings are inaccurate, or not adequate, what you are really talking about here is risk.

Stijloor pushed the right topic...are either of your caliper types adequate? You may both be wrong...
Data really helps.

After MSA on our calipers, we threw them all out and got a CMM.
Dial vs digital didn't matter, they both failed.

If you want to go digital based on a risk assessment, did your risk assessment include him not being able to (or difficult to) read the digital?

If this is a preference thing...test your gages.
If this is a risk assessment decision by management, then explain the decision in those terms...and it ceases to be a discussion and becomes a defense of 'decision already made'.
 
N

notadog

Thank you all for your responses

Let me ask it this way:

I can buy only one caliper. But I have to compare two different styles of calipers.

How do I compare the two to find out the best for my operation?

One Operator
Two Calipers: One Digital & One Dial
10 parts

How do I determine which caliper is better? I need to measure two parameters Length and OD.
 

Project Man

Involved In Discussions
I have had this conversation and study. The "Old School" machinist with his calipers (that he's been using for 20 years) was able to measure the parts within .0001" - .0002" of the CMM measured result. The digital calipers, because of the rounding 5th digit, did not fair quite as well. I've also had an inexperienced operator use digital calipers and fail a measurement test because they weren't using the tool properly/consistently.
A personal preference is not easily changed. Unless you have data that would force his hand I don't think you should.
 

howste

Thaumaturge
Trusted Information Resource
Thank you all for your responses

Let me ask it this way:

I can buy only one caliper. But I have to compare two different styles of calipers.

How do I compare the two to find out the best for my operation?

One Operator
Two Calipers: One Digital & One Dial
10 parts

How do I determine which caliper is better? I need to measure two parameters Length and OD.

As has already been recommended above, do a measurement system analysis. Gage R&R studies would be where I would start. It will give you data that will show the ability of each gage to measure the parts at the tolerances you're using them for.
 

Michael_M

Trusted Information Resource
There is another thing to consider in the risk department: gage damage. Dial Calipers use a physical gear. I, personally, have destroyed a few pairs of Dial calipers when I get a chip stuck in the gears. If a chip causes a tooth to skip, will the operator 'know it' and what are the risks of making bad parts (again, been there done that, once).
 
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