Tool sellers

Looking to buy a new square, saw, plane, or ?? Have a question about which sharpening stone to buy? This is the place.
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Brian
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Re: Tool sellers

Thu Aug 03, 2017 1:31 pm

From what I've gathered it is 1 minute = 1 bu. So explained to me a while back that not many chisels are actually made to metric measurements, they're made to shaku then loosely converted to nearest mm, that is why they often seem to be more accurately imperial than they are metric.
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Chris Hall
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Re: Tool sellers

Thu Aug 03, 2017 2:36 pm

The term for a plane that is 1-sun, 8-bu in width, is 一寸八分, issun-hachi-bu, which is abbreviated by carpenters as 寸八 sun-pachi.

Google translate doesn't know what to do with the term '寸八' sun-pachi, however when it sees the clumping '八分', it translates that, totally accurately, as 'eight minutes'. You see, the kanji '分' is a very common one and has several readings and meanings, some minor and some major. Among them:

BUN dividing, partition

FUN, ~PUN: minute (of time/arc), unit of weight, about 375 mg

BU: rate, percentage, one percent; thickness, (unit of length, about 0.303cm)

wakaru: understand

wakeru: divide, split up, separate, isolate, distribute; distinguish

wakareru: part, leave; branch off, be divided

Three 'Chinese' readings and 3 'Japanese' readings for that character. More readings than most kanji. When you are describing time and using the character '分', the 'FUN, ~PUN' reading is used as in, 5-minutes (五分), go-fun, or 7-minutes (七分) nana-fun, 8-minutes (八分) happun, etc..

When talking about measurements though, the reading of ~BU is used, not FUN,~PUN , so -5 units of 0.303mm- is termed go-bu, using the exact same characters 五分 as for 5 minutes of time.

Since the meaning of '分' as a unit of length. 1/10 of a sun, is a minor and slightly esoteric one compared to the rest, Google Translate takes the much more obvious interpretation of '分' as minutes of time.

ーーーーー

Besides the 70mm plane, the planes in the most common sizes are named as follows:

一寸六分 issun-roku-bu, which gets shortened, in carpenter lingo, to sun-roku. A 65mm plane

一寸四分 issun yon-bu, which gets shortened, in carpenter lingo, to sun-shi. A 57mm plane.

As to the measurement of Japanese planes, this is an area of some confusion.

If you look on Mandara-ya's website, they show a sun-pachi plane as measuring 70mm, however the actual measure of 1-sun is 30.3mm, and 8-bu is 24.24mm, which makes a total of 54.54mm. A 70mm width actually equals, in traditional Japanese measure, two-sun and three-bu, 二寸三分

Huh? Why is a plane with a 70mm blade called sun-pachi, when that measures 54.54mm?

Now, a 70mm plane body, with the ears trimmed, will be fitting in a plane body with a mouth opening of around 65mm, and the ears trimmed slightly inside of that mean the blade length is around 63mm. Nowhere is there is a 54.54mm dimension it would seem.

Well, here's the scoop. The term sun-pachi, and the 54.54mm width refer to the effective cutting width of the plane. The blade itself is 70mm wide, but after you trim the blade ears and slightly feather the cutting edge to zero at the corners, you are ending up with an effective cutting width of around 54mm for general use.

It is said a carpenter is skilled when they can use a sun-pachi plane to produce a thin 2-sun (60.6mm) wide shaving.

Planes are a special case when it comes to describing the width. For chisels, the actual width designated in Japanese measure, say 6-bu, is the actual width, and you can convert right across from sun/bu to mm. A 6-bu chisel would therefore be 18.18mm wide, or thereabouts.
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Chris Pyle
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Re: Tool sellers

Wed Aug 09, 2017 11:29 am

Thanks Chris (& Brian/Daruma),

That's exactly the type of info I would never figure out. Appreciate the help.

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