Which Digital Calipers

[Joel]

I need to replace my 6" digital calipers. I need good accuracy without breaking the bank. There are many choices, and most of the ones under consideration claim .001 accuracy. I know many here have a strong preference for Mitutoyo, but they make several similar models with a broad range in price. Any specific recommendations?

[Al Messer]

Joel, Digital Calipers are a lot like women and sports teams: everybody has his own favorite. Wish I could REALLY advise you, but mine are an Oriental import that cost me the princely sum of $24.95. But, they are accurate enough for what I do.

[BillH]

I love my 8" digital caliber I got from HF for 25$ on sale. They are the stainless steel ones.
I also have a nice mitutoyo 6" dial caliber that I used for first time in a long time, and oh man, I forgot how nice and silky smooth it is.

[PeteM]

Mitutoyo's best digital calipers have an SPC output. This is one thing you probably don't need, and can save you $30 or so. I wouldn't buy their cheapest units (some have said less accuracy) but either a conventional digital or a water-resistant digital if that's a concern for your application.

[Joel]

Thanks, I still have a good set of the inexpensive ones. I need something good to .001 or better, and I figured many here have had good luck with some particular calipers.
J&L currently has on sale, a Mitutoyo MT5-00652E for $139. A B&S Dura-Cal IP65, 599-571-10S for $110. And a Starrett 721A-6/150 for $122. None list accuracy in the catalog.

[This message has been edited by Joel (edited 12-09-2003).]

[JCHannum]

The best digital calipers I own are Mitutoyo Absolute Digimatic. Read to 0.005". Cost $5.00 & new battery.
I use my Starrett dial calipers for most work. I just have never gotten used to using a digital when machining. Same with indicators.

[BillH]

How about micrometers? Am I at a huge disservice for not owning one? On my axles I need to cut, I have been using my digital calibers, and some tolerances are close to .0005.
Hmmm...

[Evan]

Joel,

According to the technical specs on the Mitutoyo website the accuracy of nearly all thier digital calipers is +-.001. Some of the line have readouts with resolution of .0005 but still only accuracy of +- one thou. That isn't good enough for me which is why I still use dial calipers.

[JCHannum]

A digital caliper that reads to 0.005" has an accuracy of 0.001".
You cannot expect better than 0.001" from dial calipers due to the mechanics of the rack & pinion drive and inherent loss of accuracy and repeatability in the mechanism not to mention the effect of parallax in taking the reading. No dial calipers that I know of spec better than 0.001" accuracy.

[Joel]

Thanks,
BillH, to work to tight tolerances you need to use micrometers. Even cheap ones will work well for you compared to calipers.
Evan, when I am working to close tolerance, I use my mics. Often tolerances are not required to be that tight, and digitals are a great expedient. Years ago, I almost bought a Mitutoyo until I found out it was only accurate to .005. Glad I checked.
JC, my cheapies read to .0005 but are only good to maybe .003, good for roughing only. Do you think the Absolutes are superior to the Dura-Cals?

The B&S are looking pretty good. I can get them for $95 from the mfg. The Mitutoyo Absolutes are still right there though for under $100. Starrett doesn't give an accuracy on theirs, so I am ruling them out.

[chipeater]

Starrett are accurate to .001.

See

http://catalog.starrett.com/catalog/catalog/groupf.asp?GrpTab=Feature&GroupID=627

[Evan]

JCH,

I presume you mean .0005, not .005. Resolution and accuracy are not the same. Accuracy depends upon the quality and linearity of the encoder mechanism. Resolution depends upon the display capability. Even if the display can show steps of .0005 if the accuracy is only +-.001 then then possible error range is .002. A dial caliper may not be specified as having accuracy better than .001 but the needle position can be interpolated to better than that and the accuracy tested with traceable standards like guage blocks. You can't interpolate a digital display. Also, all digital displays have an inherent least significant digit inaccuracy of +- one count. In the case of the Mitutoyo since it can display .0005 steps that means the one count error band is +- .0005, or .001. That is display accuracy (resolution), not measuring accuracy.

One more thing; I often need to make things the same size. The absolute dimension isn't important. Under those conditions I can read the dial down to maybe .00025 or so. No can do with a digital.


[This message has been edited by Evan (edited 12-09-2003).]

[Evan]

BTW, good quality ball bearings (ABEC-SP grade) make excellent calibration tools. The mean and max od is specified to +.0000 and minus .0001" for bearings under 18mm and +.0000 and -.00015" for larger ones up to 30mm. Even the lowest grades have decent specs, no more than +.0000/-.0003. The standard principle when calibrating is the standard should be ten times more accurate than the measuring tool.

[This message has been edited by Evan (edited 12-09-2003).]

[JCHannum]

Joel, I think any of the better Mitutoyo calipers are probably pretty good, only get the features you need, the absolute retains the zero setting when shut off, which is nice, but not necessary. SPC output also adds to the cost as mentioned. I would avoid the plastic Mitutoyos. Travers has the 6" MyCal Absolute at $84.95 right now.
Evan, yes, I lost a decimal place, meant 0.0005". It is impossible to accurately interpolate the scale on a dial instrument unless it incorporates a mirrored scale to eliminate parallax as I stated. I do not know of any dial calipers with this feature. Just tilting the dial on my Starrett changes the reading at least 1/3 of a division.

[Evan]

Chip,

"Starrett are accurate to .001. " Nope. They are accurate to +-.001. That is a two thou range so the reading is somewhere within a two thou band of possible error. That is completely unusable for me.