The Survey of Antique Fractional Gage Blocks

Ulma Doctor

Infinitely Curious
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i was surfin' on the site that sounds alot like E-Pay....

i found a wonderfully handcrafted set of antique fractional gage blocks that spoke to me :grin big:
so i got them!

IMG_3414.jpgIMG_3415.jpg

not knowing the accuracy of the blocks,
i decided to clean and measure them and cross check with other mic's and calipers so i could assess their usefulness

IMG_3417.jpg

after cleaning the blocks with rubbing alcohol i started the survey.
for the first measurements, i used the trusted Mitutoyo .0001" digit micrometer,
and just for giggles i ran the blocks through the jaws of the Harbor Freight Digital Calipers to see the differences
i also cross checked with lower resolution mics to test the differences between the earlier findings

for those interested, here is the results of my less than laboratory test....{EDITED}

corrected survey.jpg
[Disclaimer- the testing was not performed under laboratory conditions, so take the readings with a grain of salt ;)
{the ambient shop temperature was below 70°F}
the mitutoyo digit mic was cross checked against 2 other 1" gage blocks as well as against the .401" gage blocks from 2 different sets ]

i was blown away as to the accuracy of the toolmaker who produced these fractional gage blocks
most were dead nuts to a +/-.0001" on 7 of the 17 blocks tested, 10 blocks were dead nuts no error at .0001" o_O

what was equally amazing to me,
was that the inexpensive Harbor Freight 8" digital calipers, read similar findings compared to the Mitutoyo digit micrometer.

all of the other cross checks had similar readings, to a lower resolution of .001'.
i didn't feel compelled to record the lower resolution cross checks.

Results:
my hat is off to this craftsman.
i ponder the skill and tenacity it must have taken to produce these nearly perfect gage blocks.

i feel great pride to introduce these tools into my home shop.
not for anything i did, but for having functional works of art to make other creations from.

as always,
thanks for reading :grin:
 
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Pretty impressive that they are that accurate. Nice score. Mike
 
The 11/16" block should be ,6875" so -.0004".
I mistakenly wrote the .6874” wrong and transposed the error to the ten thousandths when I recorded it :(
i edited the survey above to reflect the mistake on my part
 
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Functional works of art, indeed! Thanks for posting. You got yourself a winner, there ... too bad they didn't come with a history. That would have been fascinating.
 
At this point, you are within the range of error of the micrometer. It might be worthwhile to have them calibrated by a metrology lab.
 
Good score Mike and thanks for sharing. You just never know what's going to show up. Any guess why somebody would want a fractional set of gage blocks? Precision woodwork? A decimaphobic? Inquiring minds wanna know :)
 
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