digital calliper

[BANYAN]

Hi, I have two sets, one metric the other Imperial (Fractions) and until recently I used them all the time until I became aware of a small problem I have yet to resolve.  I was wondering why some of my measurements were very slightly out and finally recognised that the calipers were not truely zeroed (they differed from each other and from a "engineer" certified quality miocrometer).  We are only talking a few hundredths here so it is not critical for many jobs; but I would love to know how to truely zero these? (I can reset the readout to zero, but the inscribed vernier scale is not zero when the jaws are fully closed (this is verified by the micrometer which indicates / measures a difference in size equivelant to the difference shown on that scale.)

 

CraigB@ thanks for the reminder in your earlier post which alerted me to this possibility; I think I may have to invest in a better quality metric version; the Imperial measurement version is slightly out, but much better and I can live with it.

 

cheers

 

Pat

Edited October 23, 2013 by BANYAN

[Modeler12]

Pat, perhaps I misunderstood your post, but both of my calipers (digital as well as the dial type) have a zero adjustment. In other words, when I close the jaws and there is a reading other than zero, I push the zero button on the digital or turn the dial on the other one.

If you encounter deviations after that, then there is a problem with the instrument.

Edited October 23, 2013 by Modeler12

[HIPEXEC]

I use mine all the time and not just in building my model.

[BANYAN]

Hi Jay, yep, I have the same understanding of zeroising (the readout) not the tool itself.  However, as I said the unusual thing is that if I measure the same article/item, all three give a different result.  I understand that if I zero the readout, the amount of movement is relative to the starting point (zero) and therefore all readings should be the same. The micrometer (which has been tested/calibrated and certified) I trust to be the most accurate.  The readout given by the Imperial (fractional) digital readout calipers is not far off, but the cheaper (version/type most folk seem to be using) are out a bit. 

 

I have noticed that when the jaws are fully closed on the metric calipers and I 'zero' the readout, the etched vernier scale on the main slide (?) is out (not registering on the 0 line) and it is very close to the difference in accuracy of the measurement between the micrometer and the caliper also.  This is the enigma - if the readout measures the relative movement to calculate the 'measurement', it should be accurate no matter what?  Essentially, I believe that after a while the caliper readout of the measurement may become suspect, possibly wear on the internal parts?

 

I am not sure how the distance reading is converted to the digital readout value, but I am beginning to think that the mechanical component of the sensor (or however it is done) may wear over time and that is why I am getting the slight error in measurement.  This became evident after having to remeasure my micro-drills on several occasions as one caliper gave me one reading, and the other a different.  A couple of hundreths (when rounded) makes a difference in determining whether to use the drill as say a 0.9 or 0.85mm drill.  I double checked these sizings with a gauge plate (not the most accurate means) but the results using the micrometer were much better than using the metric calipers.

 

I have reverted to using my micrometer until I get a better quality caliper (with digital readout) and I will be sure to check how accurate they are first this time

 

cheers

 

Pat

[BANYAN]

Hi folks, further to my last post, I am now wondering how many of us have taken the time to check if the measurement determined by the caliper is actually accurate (at purchase and then at intervals) - I certainly didn't  

 

I will now be checking my next purchase for a reasonable degree of accuracy, and ensure I check it reasonably regularly to ensure a consistent measurement accuracy as well as confidence in the caliper.  For most uses in ship modelling, having a super-accurate readout is not that important, but a reasonable degree of 'consistent' accuracy from these tools is important I think?

 

cheers

 

Pat

[Richard Griffith]

I too prefer the dial readout as it is easy to see and read.  I had a digital but it ate up the batteries and required zeroing with every measurement.  It was a cheap one so my experience with digitral may be skewed.  But the dial ones are my most used tools in the shop. 

 

The tool should be checked preiodically for accuracy.  Chips on the gear or rack will throw off the accuracy.  Since we are not building for the aerospace industry, take measurements of known dimensions such as your one two three blocks, or the width of your steel rulers.

 

If at first you don't fricassee, fry, fry again...............

 

Duffer

[Q A's Revenge]

For most jobs Digital calipers are pretty good and easy to read but if you want accuracy a Micrometer is hard to beat. Bear in mind though Mic's only have a small measuring range.

[Modeler12]

I took both calipers I showed above and a two inch micrometer that came with a 1.000 inch 'standard'. It is the black ring in the picture below.

After 'zeroing' both calipers (which was not necessary since they were still set from before), I measured the 'standard'. My dial calipers were dead on 1.000 inch and the digital fluctuated between 1.0000 and .9995 inch.

 

I don't have any gauge blocks larger than the 1.000 inch, but I am satisfied with what I have. I really think quality has a lot to do with this. As we all know you can buy 'calipers' that are real toys and those made by a reputable company. Then there are many in between.

I might add that the dial calipers I show is a 505 series Mitutoyo (about $120) and the digital is an inexpensive Pittsburg (it was a gift but sells for $20). I can really tell the difference in just the way the two 'feel' and the finish. And, as I have said before, I like the dial much better because it gives me a 'indication' of where I am (plus and minus what ever).

Edited October 24, 2013 by Modeler12

[Q A's Revenge]

I bought this Mic checking set very cheap a while back. Can't say it gets much use though! :-)