What is the correct Working Standard for Digital Micrometer?

[Dongzkie]

What is the correct working standard for digital micrometer?
I am confuse as far as i have known gage block is the right working standard for micrometer but we are using pin gage. I've asked one of my colleague he told me that we are measuring diameter of our product. Is this really right?

[Jim Wynne]

In Reply to Parent Post by Dongzkie

What is the correct working standard for digital micrometer?
I am confuse as far as i have known gage block is the right working standard for micrometer but we are using pin gage. I've asked one of my colleague he told me that we are measuring diameter of our product. Is this really right?

It depends on what you mean by "working standard." In general if you're calibrating a standard micrometer, blocks are preferable because they engage the entire contact surface. If you're using a some form of standard on the shop floor to verify a mic prior to use, and the pins simulate typical workpieces, then pins are probably the way to go.

[step30044]

You will need to account for the accuracy of the pins and micrometer as well as the condition of the pins

[Jim Wynne]

In Reply to Parent Post by step30044

You will need to account for the accuracy of the pins and micrometer as well as the condition of the pins

That's true, but it would also be true of blocks.

[Dongzkie]

thank you very much for the advice.
As for now we are using Class Z gage + which has the accuracy of 0.0025mm use in Mitutoyo digital micrometer has accuracy of 0.001mm and i don't think this is acceptable.

[Jim Wynne]

In Reply to Parent Post by Dongzkie

thank you very much for the advice.
As for now we are using Class Z gage + which has the accuracy of 0.0025mm use in Mitutoyo digital micrometer has accuracy of 0.001mm and i don't think this is acceptable.

What are the tolerances of things you're measuring?

[JRKH]

I must say that, I am not particularly convinced that using pins is a good idea. The justification that one is measuring "round parts" doesn't convince me.

The issue of checking round parts may effect the wear pattern (flatness) of the anvil and to a lesser extent the spindle but if this is significant then it is something best evaluated in a cal lab setting and not on the shop floor. The wear on the Anvil will likely be in a single direction due to fact that it is fixed, and the particulars of measuring round parts. The wear on the spindle will be different and less pronounced depending on the number of different diameters are measured due to the fact that the spindle rotates and thus contacts the surface differently with different dia's.
The readout, digital or analog - should have no bearing on the standard used.

That is just the gut reaction of an old machinist who ran turret and engine lathes for many years and measured thousands and thousands of round parts, before even coming to the inspection/quality field.

Peace
James

[Jim Wynne]

In Reply to Parent Post by JRKH

I must say that, I am not particularly convinced that using pins is a good idea. The justification that one is measuring "round parts" doesn't convince me.

The issue of checking round parts may effect the wear pattern (flatness) of the anvil and to a lesser extent the spindle but if this is significant then it is something best evaluated in a cal lab setting and not on the shop floor. The wear on the Anvil will likely be in a single direction due to fact that it is fixed, and the particulars of measuring round parts. The wear on the spindle will be different and less pronounced depending on the number of different diameters are measured due to the fact that the spindle rotates and thus contacts the surface differently with different dia's.
The readout, digital or analog - should have no bearing on the standard used.

That is just the gut reaction of an old machinist who ran turret and engine lathes for many years and measured thousands and thousands of round parts, before even coming to the inspection/quality field.

Peace
James

I'm going under the assumption that the OP is using calibrated micrometers and calibrated pins (or other "working" standards), and using the standards on the floor as just a quick verification that things are as they should be. When doing a full calibration, blocks of the appropriate class should be used. In the circumstances described by the OP, where diameters are being measured, I don't see a problem with using pins of the appropriate size to do the verification.