this post was submitted on 31 Mar 2024
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string would be tough at that scale but weirdly might be easier to make that measurement with than a ruler. just cut your string to 9.5mm length, then divide it by three, one of those divisions is your target length and you even have the other two to check your division's margin of error against.
to calculate and measure with a ruler would have you measuring 3.16666... which i would not be able to measure with a ruler. now a vernier caliper would be the right tool to make that measurement, and even if mine only had tenths of a millimeter id just round to 3.15mm and mark in between the mm graduations when forced to use that group of tools.
of course that's if you know how to use a set of calipers. its not as easy as one might think.
lets not forget that your response to the one third of 9.5 conundrum, which was posed by a metric defender, is:
which is literally not true as i have explained about the 24th scale ruler and even my digital calipers don't do repeating digits or express portions of metric measurements in fractions.
of course, in a real world situation i'd never be trying to mark 3.1666...mms because it's 1/3 of a thou under 1/8 inch. i'd just mark an eighth of an inch like a normal person.
even using a calculator to figure out the length suggests that a person in that conundrum stop using the metric side of their ruler.
they weren't a metric defender
what scenario is there in your mind where you'd need a precision answer to what 1/3 of 9.5mm is, but also not have access to a calculator? and of those scenarios, how many of them would be solved by the knowledge that 1/3 of 1/8 is 1/24? i'm willing to bet the answer is more or less "none".
and for those that do exist, you can also get drafting rulers that give you 1/3rds of metric measurements.
the accuracy of your equipment isn't somehow better because you're dealing with fractions rather than decimal points
you're right. the person who initially brought up 9.5 was comparing it to the sae equivalent 3/8 (9.525mm, but whos counting).
the reply was what i was thinking of, the obvious answer: "what if you need to divide by 3?"
so good eye.
one scenario when i'd want a precision answer to 1/3 of 9.5 but also not have immediate access to a calculator is when woodworking. you know, seeing as how 9.5 is (the actual metric defender this time's approximation of) 3/8... and there's no way that a calculator would help me there because the result of 9.5/3 is 3.16, a length i'd need at least tenth millimeter vernier calipers to accurately scribe. even 9.525/3 is 3.175, a measurement that requires um precision to scribe!
the inch side of my ruler, however, is graduated in eighths of an inch and i can make that measurement easily with it.
i've also used a third measurement of a known diameter when drilling holes in metal to use a technique described in machinerys handbook to cut slots.
you were the one who asked what a third of an eighth was. i'm not sure why. why did you bring up a third of an eighth? was it because you thought it would allow a person to more easily answer the question what is 1/3 of 9.5?
i guess my real question is this:
how does a calculator help you make more accurate measurements?
using a ruler to measure a length of 1/8" is as accurate as using a ruler to measure a length of 31mm and eyeballing 2/3 of a mm
the bottleneck at that point is your eyeball and pencil lead, not the unit of measurement
well, it's 3.16 mm, not 31.6, but i get your meaning.
in that case if you wanted to be real precise, you'd measure from the left or right side of one graduation to the same side of the next graduation. using that technique a person could get a better 1/8" off a ruler than someone eyeballing fractional mms would.
I still don't see how a calculator helps though.
well yeah, because 1/8" is 3.175mm
1/3 of a mm is a distance between 1/64" and 1/128"
mechanical pencil lead is only about 0.4mm
don't ask me ask the person who posed the "what's a third of 9.5mm" question
Usually when I’m making a precise line, I’ll put an edge on the pencil lead so it will make a mark thinner than its diameter.
I seem to remember you as the one who brought up calculators, but I’m open to being mistaken.
even if you're in a situation where it's somehow possible to manually draw 1/3 of a mm to any accuracy, 1/3 scale draft rulers still exist for metric, so it's equivalent
because as soon as you have access to a calculator, "off the top of your head" is an irrelevance