Odd micrometer question.

[beezapilot]

I know that it is a sign of mental illness, but I'm a sucker for old orphaned tools. Picked up a Slocum micrometer with patent dates of May 12th, 1890 and April 13th 1897. On the barrel it has the standard divisions for tenths BUT under that scale there is another that breaks the inch into eight major divisions, with each of those broken into 4 divisions (1/32nd). I'm unfamiliar with anything that would use that form of division / measurement. Any sage and worldly gunsmiths / machinists that know what this was used for? Built in fractional measurements?

Yeah.. kept playing with it... major increment X4, add the number of dividing lines for a measurement in 32nd's, easy math. Perhaps for providing measurements to those lowly carpenters who must have been tickled to get a measurement of 23/32nd's.


Ha! Wo needs decimal equivalent charts anyway....Attachment 225010

[JSnover]

Probably just trying to satisfy everyone. If it's made well enough it's not a bad idea, you can convert to whichever increment you like.
I've seen a caliper with multiple scales on the dial but the entire thing was plastic.

[ulav8r]

At the time it was made, most machine components were made to fractional measurements.

[TCLouis]

Made for a lumber mill?

[uscra112]

At the time it was made, most machine components were made to fractional measurements.

ulavr8r has it right. Decimal inch measurement wasn't universal in machine shops, even as late as 1914. You'll find this on 19th century patent drawings, sometimes with numbers like xxx/128th inch.

Army procurement standards killed off fractional inch measurement for precision machinery during WW1. They also forced machinery makers into using a nationally standardized system of screw threads, for which we should be eternally grateful.