Which dial caliper to trust? (This was worded as "dial indicator" before. In the end a dial is a dial)

[jhearons]

I don’t mean to hijack this thread but I’ve noticed that when I hold my index finger and thumb apart to measure dog turds on the sidewalk I get a different measurement against the yardstick at home for my left hand versus my right hand. Do you think a Chinese person would get more consistent results doing the same thing?

 

[jim rozen]

Sure you can measure tenths with a dial caliper - do it all the time, ten of 'em at a time!

 

[neanderthal mach]

What eKRETZ and others had to say is indisputable. Adding to what's already been mentioned. The world wide allowable deviation standard for metrology equipment is + - one count. The measurement deviations you mentioned between all four calipers are well within the allowable tolerance there designed for and capable of, so there all correct. Trying for 10ths or even half thous with calipers isn't ever going to happen and be repeatable enough to be trusted. That's literal tooth fairy or unicorn territory.

 

[ttrager]

Out of four calipers for example:

Two Starrett 120As read .014 slightly over the line but not at .01425. One caliper is very lightly used and the other is my companion.
One import digital readout caliper says .0145, and my Mitutoyo Limited Edition almost never used says .0145.

Looks like the Starrett's are off. Didn't expect this and wonder if others see things like this.
I measured everything more than once under clean conditions. I measured the example with a guitar string.
Once the jaws close that's it. No free play. I tried a little force on the flats, not the front 30 degree bevels.

In real life, the digital indicator is never used because I didn't trust it and I don't like dealing with batteries. Although the display blinks
when the battery needs to be replaced. The Mitutoyo is almost never used as well as one of the Starretts.

My Mitutoyo 8" digital calipers are remarkably accurate, and repeat nicely. This is said within the context of calipers mind you, which are incredibly sensitive to deviations in hand-use person to person given those great, big, long jaws. I just measured a 2" ceramic gage block @ 2.00" even, a 1" block @ 1.0005, and a .650 block @ .6505.

I take care of them mind you, and I don't lend them to anyone else. I'll take digital calipers over mechanical's every day.

Having said all that, what other's have said is common wisdom, which I'm sure isn't news to you: "Precision" measurements in my shop are done with Micrometers (my Mitutoyo digital mics are great), or Indicating Micrometers (we have Mitutoyo and Etalon's), Optical Comparator, or LaserMike.

 

[M.B. Naegle]

I THOUGHT is was about time for this topic to come up again...

 

[DDoug]

View attachment 371243
I THOUGHT is was about time for this topic to come up again...

It is the insanity that occupies the OP.