Decimal inch Sashigane now on Amazon

Looking to buy a new square, saw, plane, or ?? Have a question about which sharpening stone to buy? This is the place.
Gadge
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Re: Decimal inch Sashigane now on Amazon

Mon Feb 22, 2016 10:06 pm

Thanks for being so lenient with me Chris. I'll give up my campaign.
I guess if you live in the centre of the universe there's no need to conform.
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Chris Hall
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Re: Decimal inch Sashigane now on Amazon

Tue Feb 23, 2016 12:18 am

If this matter is truly important to you, you could always make contact with a US group that has been advocating for metric for 100 years:

http://www.us-metric.org/

I'm sure they would welcome your ideas and enthusiasm for the subject.

Or there is this US metric group, whose homepage shows a version of the same exact map - perhaps they will have insights about how helpful the map has been for winning hearts and minds:

http://www.metric4us.com/
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Evans
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Re: Decimal inch Sashigane now on Amazon

Tue Feb 23, 2016 8:29 am

Chris Hall wrote:No measuring system is more 'rational' than any other. They are all artificial constructs - metric more perhaps so as it is based on such standards (when it comes to the metre) as the distance travelled by light in a specific fraction (1/299 792 458) of a second.
Well, originally the meter was defined as "1/10,000,000th the distance from the Earth's equator to the North pole", which in no way counters your point about choices, but is more rational. Based on that statement, anybody can re-derive the approximate length of a meter from calculations and measurements of the world we live in.

That said, I get annoyed when a ruler isn't marked in inches down both edges because I have to pay attention to which edge I'm using: the inch edge, or the meaningless edge.
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Re: Decimal inch Sashigane now on Amazon

Tue Feb 23, 2016 10:27 am

Evans wrote:
Chris Hall wrote:No measuring system is more 'rational' than any other. They are all artificial constructs - metric more perhaps so as it is based on such standards (when it comes to the metre) as the distance travelled by light in a specific fraction (1/299 792 458) of a second.
Well, originally the meter was defined as "1/10,000,000th the distance from the Earth's equator to the North pole", which in no way counters your point about choices, but is more rational. Based on that statement, anybody can re-derive the approximate length of a meter from calculations and measurements of the world we live in.

That said, I get annoyed when a ruler isn't marked in inches down both edges because I have to pay attention to which edge I'm using: the inch edge, or the meaningless edge.
Yes, the metre was originally defined as 1/10,000,000th the distance from the Earth's equator to the North Pole, the quadrant of the earth's circumference, and surveying that took 6 years. Curiously enough, they undertook that survey using a standardized non-metric measurement called the toise. A toise is like the fathom, about 6' long. The toise was divided into 6 pieds, or "feet" and 72 pouces (inches). The pouce was divided into 12 lignes (lines). So, 864 lignes = 1 toise. Later investigation determined that, at the time of the survey, 1 toise equaled 1,949.03632 mm. Yes, a metre was determined by surveying using imperial French measures.

Previous survey work lead to the provisional determination that 1/10,000,000 of the Earth's equator to the North Pole was 443.44 lignes - this became the official standard for the metre. If a toise is 1,949.03632 mm, then 1/864th of that, 1 ligne is 2.255829mm. So, multiply that by 443.44 and you get 1000.32484460mm.

The eventual official survey result lead to the provisional 443.44 lignes being changed to 443.296 lignes, which equals 1000.0000052207...mm. A lot closer to the modern definition but still not quite correct. This 443.296 lignes distance however became the reference standard. Later it was determined that the survey value was slightly too short and the metre was redefined, but not officially, as 443.31 lignes: later work increased the value to 443.39 lignes. Even though the scientific standard was revised twice, the initial standard of length of the metre stayed as it was. How rational is that?

Anyway, two issues here, to address your point Evan more succinctly (it is my hope at least...):

- numbers like 1,000,000, 10,000,000, 1/10,000,000 etc. are not intuitively graspable by humans. Yes, many can intellect such numbers, and we sure have counting systems to go there, however, biologically speaking we are set up to deal with much smaller numbers in terms of cognition. In our normal life experiences, our brains have become capable of representing small numbers, but helpless at accurately reflecting very large ones. So, making a metre 1/10,000,000 of a distance we cannot apprehend in the first place is not terribly helpful.

-the intellection that setting the length of the metre as 1/10,000,000 of the earth's quadrant -the meridional definition - might seem rational and reasonable, something that could be agreed upon by all, however a problem crops up in that the earth is not a perfect spheroid, but an oblate spheroid. Along which longitude one measures is going to affect the result, plus doing those surveys in each country is way impractical, for a number of reasons .

Also, defining a metre (or any other length standard for that matter) by a physical object, like a platinum bar, is going to lead to problems with wear and tear on that bar, and leads to difficulties in spreading the standard without actually moving the bars from place to place, etc.

The contention that "anybody can re-derive the approximate length of a meter from calculations and measurements of the world we live in" is incorrect I think, if you base it on the 1/10,000,000 of the earth's quadrant idea.

Others realized, and early on, the shortcomings inherent in the definition too. In the 1960's the metre was redefined as:

"The metre is the length equal to 1 650 763.73 wavelengths in vacuum of the radiation corresponding to the transition between the levels 2p10 and 5d5 of the krypton 86 atom". This measurement was undertaken in a perfect vacuum.

Do you intuitively understand how far that is? I don't personally. It's perfectly rational to make it equal something like that, and it is at least a method which is readily internationally reproducible in a laboratory.

Later on, it was discovered that the krypton wavelength line was found to be asymmetrical, so different wavelengths could be found for the laser light depending on which point on the krypton line was taken for reference.

Therefore that length standard for the metre was abandoned in favor of the current one,

"The metre is the length of the path travelled by light in vacuum during a time interval of 1  ⁄   299,792,458 of a second"

I put it to you that humans cannot intuitively grasp either the speed of light or 1/299,792,458 of a second. It is very specific and exact yet seems a highly artificial construct. They could specify any length measurement you like, inches, shaku, whatever, by some amount of distance that light travels in a vacuum - it would be equally hard to grasp for most folks.

And I say that in the world of woodworking, we are dealing with intuitively-graspable numbers nearly all the time. Whatever system you use, it matters only that you are conversant with it and are not confused by it. I tend to prefer inch scale myself but am frequently converting measures here and there to metric for certain machine settings. I like the high factorability of the inch as well.
Gadge
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Re: Decimal inch Sashigane now on Amazon

Tue Feb 23, 2016 5:52 pm

Earlier this month, in Australia, we celebrated the 50th anniversary of the change to decimal currency. When I was at school we still used the British system of 12 pence to a shilling and 20 shillings to a pound. There were also halfpennies and farthings (quarter pennies). It was very cumbersome to calculate and the change to decimal was a breath of fresh air.
Also until the mid 70's we used the British weights and measures system, which was also cumbersome. Likewise, the change to the metric system was another breath of fresh air even though we loved our feet and inches. As a designer of bubble jet printers I work with micro scale dimensions and use SI units to calculate pressure, stresses etc. With a decimal system it's so easy to jump from micron to millimeter and meter all in your head without the need for a calculator.

I've used both systems and for my money, metric wins hands down.
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Evans
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Re: Decimal inch Sashigane now on Amazon

Wed Feb 24, 2016 9:05 am

I hate getting into these arguments with you, here in your own house and all. When I chime in with my opinion, I seem to set something off in you. If this is aggravating, I'm sorry. (If you enjoy arguing, I'm not sorry. ;)
Chris Hall wrote:Yes, the metre was originally defined as 1/10,000,000th the distance from the Earth's equator to the North Pole, the quadrant of the earth's circumference, and surveying that took 6 years.
Eratosthenes (in 5 BCE) derived it mathematically to within 1% error based on observations of the sun's angle over a distance of just 500 miles. Following your point about large numbers, 1% is quite an error, but still he had the right idea.

All this mucking about with wavelengths of light and such is just attempting to base the meter on something more exact, and (as you say about platinum bars) unchangeable. It's an interesting and necessary occupation for scientists, but I agree it has little meaning in the mundane world.
-the intellection that setting the length of the metre as 1/10,000,000 of the earth's quadrant -the meridional definition - might seem rational and reasonable, something that could be agreed upon by all, however a problem crops up in that the earth is not a perfect spheroid, but an oblate spheroid. Along which longitude one measures is going to affect the result, plus doing those surveys in each country is way impractical, for a number of reasons.
Even if the Earth were a perfect sphere, the exact distance from the equator to the pole would depend on the precision you wanted. Pi has an infinite number of digits to the right of the decimal point, after all. My point is that they tried to be rational. One cubic centimeter of water is one milliliter of volume and one gram of mass. When attempting to make a rational language of measurement for physical science, they based it on observations of the physical world. That they failed as badly as the guy who tried to make an international language for speaking (Esperanto) is the way of all human endeavor, I guess.
And I say that in the world of woodworking, we are dealing with intuitively-graspable numbers nearly all the time. Whatever system you use, it matters only that you are conversant with it and are not confused by it.
Agreed. I know my brain works in fractional inches, and there's no point pretending it doesn't. Give me a number like "1.13 inches" and I'll immediately translate it into "a sliver more than 1+1/8 inches". Which is why my joinery sucks, I know, but it doesn't help anything to live in denial. :)
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Re: Decimal inch Sashigane now on Amazon

Sat Feb 27, 2016 2:52 pm

and all this because i ordered a sashigane.
Jack Straus
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Re: Decimal inch Sashigane now on Amazon

Sat Nov 25, 2017 12:51 am

I was hoping Chris, or anyone who owns this square, could tell me what the back of the square looks like? Does it have the same 20ths scale? 16ths? SqRoot scale? Thank you.
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Re: Decimal inch Sashigane now on Amazon

Sat Nov 25, 2017 7:46 am

The uragane side has the √2 'stretch' of the front side, that is, 20ths √2. It's for regular plan hip rafter layout (mostly).
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Re: Decimal inch Sashigane now on Amazon

Sun Nov 26, 2017 12:24 am

Thanks Chris, sounds like it is just what I was looking for.

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