Standards Or Blocks To Test Micrometers?

[AR. Hillbilly]

I recently bought some micrometers on ebay. I got a Starett 0-1" and a Brown and Sharp 0-1" a Starette 1-2" a Starett 2-3" and a 6" starett that takes different anvils but only got the 5-6" anvils. I'm looking to buy standards or blocks to set and test these. I'm having no luck on ebay or any of the machinist sales places I've visited. I'm not sure what to call these or what to look for. Any and all advice would be appreciated. I'm a complete noob.

 

[kd4gij]

Here you go.
https://www.google.com/?gws_rd=ssl#q=micrometer+standards+set

 

[Holescreek]

http://www.ebay.com/itm/MITUTOYO-1-...453111?hash=item33b4c9c0f7:g:waYAAOSwiylXBFHl

 

[Bob Korves]

I would just buy a set of shop grade gage blocks and use them. I in fact do exactly that. They will fill many other needs in the shop as well. I have standards for my micrometers, but have never seen a standard of accuracy for them, plus I do not know their history, mostly being used micrometer standards. A new set of gage blocks (grade B is adequate for a hobby shop) is a known quantity, and is what is used to calibrate micrometers for continuing work in certified shops. A grade B set of gage blocks costs about the same as a set of mic standards.

I use the gage blocks to calibrate the mic standards...

 

[AR. Hillbilly]

Thank you guys so much. I don't know why my searches have been so empty. These give me a lot of choices.

 

[Tony Wells]

Remember that Jo blocks are flat, as should the anvil and spindle of the micrometer. If there is an issue with doming, dishing, or other out of flat or parallel condition on the instrument, then a flat check will really only get you part of the story.

Specific micrometer standards can (and seem mostly to) have slightly convex faces. Naturally, this will not detect the exact same problem type as a flat standard such as Jo block.

In reality, a specific micrometer evaluation kit is available. It contains optical flats to check for surface wear on the measuring contact areas. It also should be noted that a micrometer can read spot on at zero and at the usual 1.0000 limit, and not be accurate in the middle of the range because of disproportionate use in a small area. Also you should verify readings at 90° points of rotation of the spindle.

 

[TomS]

Enco lists SPI and Starrett standards on page 320 of their current catalogue. But I do agree with Bob and Tony regarding the use of gage blocks. About the same price and more uses.

Tom S.

 

[Holescreek]

Remember that Jo blocks are flat, as should the anvil and spindle of the micrometer. If there is an issue with doming, dishing, or other out of flat or parallel condition on the instrument, then a flat check will really only get you part of the story.

Specific micrometer standards can (and seem mostly to) have slightly convex faces. Naturally, this will not detect the exact same problem type as a flat standard such as Jo block.

In reality, a specific micrometer evaluation kit is available. It contains optical flats to check for surface wear on the measuring contact areas. It also should be noted that a micrometer can read spot on at zero and at the usual 1.0000 limit, and not be accurate in the middle of the range because of disproportionate use in a small area. Also you should verify readings at 90° points of rotation of the spindle.

99% of calibration labs with optical flats don't have a single individual that understands what to do about the lines they see on an optical flat and merely reject anything they don't understand. Do you really think that the average home shop machinist needs a "micrometer evaluation kit"? How many individuals are going to instinctively know how to adjust their new purchase, much less lap anvils?

 

[chevydyl]

Be careful of buying cheap new gage blocks, another member here bought some shars blocks and found that a stack up yielded as much as 7 thou offset, that's not a number I want to calibrate my Mike's too

 

[Bob Korves]

Remember that Jo blocks are flat, as should the anvil and spindle of the micrometer. If there is an issue with doming, dishing, or other out of flat or parallel condition on the instrument, then a flat check will really only get you part of the story.

Specific micrometer standards can (and seem mostly to) have slightly convex faces. Naturally, this will not detect the exact same problem type as a flat standard such as Jo block.

In reality, a specific micrometer evaluation kit is available. It contains optical flats to check for surface wear on the measuring contact areas. It also should be noted that a micrometer can read spot on at zero and at the usual 1.0000 limit, and not be accurate in the middle of the range because of disproportionate use in a small area. Also you should verify readings at 90° points of rotation of the spindle.

The Jo blocks are definitely a different feel on the mic anvils because of the flat surfaces. When the anvils of the mic are flat and parallel, you can tell by how they tighten down on the Jo blocks. You can also tell pretty easily when the mic is only biting on one side of an anvil because it wants to walk. The slightly rounded ends of mic standards do not do that, and they are more difficult to interpret, in the same way as snap gauges, trying to find the highest setting that just nicks the mic at one point.

Another plus for Jo blocks is that you can calibrate your mic at any increment you wish to test it at, not just even inches. If you are doing a critical measurement, you can calibrate your mic at the specific reading, to .0001", that you will be measuring for with the mic. Not often necessary, and perhaps overkill, but nice to be able to do for ultimate peace of mind. Jo blocks are really useful in the shop for lots of things.

I have never messed with optical flats, but might at some point.