Comparing Gage Block Sets

[erikmannie]

I cleaned the mic anvils + Starrett end measuring rod with acetone & used the wrench to get this right at 1.0000”. I’m using the tensioning knob. I will post pictures as this unfolds.

You guys may get some parallax, but this reads right at zero. I removed and replaced the standard two times, and it repeats.



Removing and replacing three times, the Shars 1.00000” gage block is always wider than the Starrett standard.



Removing and replacing two times, the Starrett standard always reads 1.0000”.



I would believe at this point that the Starrett standard and Shars gage block are not the same dimension.

 

[erikmannie]

Here I have cleaned and adjusted so that the Starrett end measuring rod will repeatedly measure to be 4.0000”. I am making sure to be very consistent with the ratcheting tensioning knob.



The Shars gage blocking is a whopping 8 tenths longer than the Starrett standard.

It was too heavy to stay in the stand for the photo.

 

[erikmannie]

I measured the Starrett 4” standard three times afterwards, and it is always right there.



It is 61°F where I am working, by the way.

I would conclude from this that the Starrett end measuring rod and Shars 4” gage block are not the same length.

 

[erikmannie]

You say that you're disappointed with the accuracy and consistency of the gage block sets.

Just curious what you meant by that. How inaccurate are they? And how do you know?

I don't have a metric set, but would like one. So I'm shopping around.

Buy my metric set. I have yet to see a reason to take it seriously.

 

[Dabbler]

@erikmannie What I see is what I'd expect. Measuring using the standard isn't going to give you premium results but it is what you have. for the 1" where the set shows it +11, that is +11 ten thousandths or +1 tenth. That is what I'm reading on your mic.

It is better to calibrate them on a AA grade surface plate using a half-tenths indicator, comparing it to a master gauge block set. I am suspicious of your 4" results, and would recommend checking both your standard and your mic against an outside standard, such as a B grade Mitutoyo gauge block, or better. I was lucky over the years to have access to lab quality surface plate and blocks. This is no longer the case.

It probably is the case that the Shars calibration is lying, but it would be prudent to check first. Cheap mic standards are notoriously fickle.

 

[extropic]

My primary concern with inexpensive gage block sets is durability.
A buddy of mine had a set and, even though I was very careful, I managed to scratch one of the blocks.
I replaced that block with a Mitutoyo.
I don't trust off-brand gage blocks.

 

[erikmannie]

@erikmannie What I see is what I'd expect. Measuring using the standard isn't going to give you premium results but it is what you have. for the 1" where the set shows it +11, that is +11 ten thousandths or +1 tenth. That is what I'm reading on your mic.

It is better to calibrate them on a AA grade surface plate using a half-tenths indicator, comparing it to a master gauge block set. I am suspicious of your 4" results, and would recommend checking both your standard and your mic against an outside standard, such as a B grade Mitutoyo gauge block, or better. I was lucky over the years to have access to lab quality surface plate and blocks. This is no longer the case.

It probably is the case that the Shars calibration is lying, but it would be prudent to check first. Cheap mic standards are notoriously fickle.

As far as I know, the Starrett end measuring rods could be off. I was trying to do the best I could do with what I have to compare apples to apples.

 

[extropic]

As far as I know, the Starrett end measuring rods could be off. I was trying to do the best I could do with what I have to compare apples to apples.

Just out of curiosity, after you used the 1" standard to "calibrate" your micrometer, did the mic read Zero when fully closed?

 

[erikmannie]

Just out of curiosity, after you used the 1" standard to "calibrate" your micrometer, did the mic read Zero when fully closed?

I did not check that.

 

[erikmannie]

Here is the same thing with some metric items. I will change the methodology a little bit, and I will set the zero with the Shars gage blocks, starting with 50 mm.