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Technique from old book

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The Baldy Carpenter View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote The Baldy Carpenter Quote  Post ReplyReply Direct Link To This Post Topic: Technique from old book
    Posted: 01 Jun 2009 at 11:48am
I was reading an old woodworking book over the weekend and it decribed a method of marking a piece of timber into exact sections which is so obvious but I had never seen or heard about before.
I am sure that this is not new to the hardened carpenters on here but in case anyone else is like me here goes.
To divide a board into 3 equal parts:
Select a mearsurement longer than the width of the board which is easily dividable by 3 e.g. if the board is 10" wide select 12"
Lay a rule across the board with 0 on one edge and 12" on the other edge. As the board is only 10" wide then the rule shall be at an angle.
Mark the 4" and 8"
Remove the rule and hey presto the board is marked into 3 exact widths.

I have spent many times scratching my head trying to devide a figure by 3 and then trying to mearsure the answer on a board to find you are 1/8" out.
Old knowledge is precious and for us that work ourselves without the benefit of working alongside other woodworkers these wee tips are fasinating.
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P Grogan View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote P Grogan Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 2009 at 8:10pm

You know Fraser you will probably remember that far better than me but your post is invaluable to me since I was taught it as Thales theorem and I have been unable to remember theorems since Pontius took up piloting.  But I am going to remember what you said thanks Big%20smile

Apparently you can use it for dovetails as well. Embarrassed
 
PG
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Post Options Post Options   Thanks (0) Thanks(0)   Quote chiseller Quote  Post ReplyReply Direct Link To This Post Posted: 14 Oct 2010 at 3:06pm
We used to do something similar when doing Technical Drawing at school.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomatwark Quote  Post ReplyReply Direct Link To This Post Posted: 14 Oct 2010 at 3:14pm
I have various old joinery and furniture making books, and they have got me out of trouble more times than I can think of, normally when I can't come up with I jig and have to find away to do it by hand.

I did a lot of handwork when I was an apprentice in the 80's and although I learnt alot of tricks from the old hands there were things we just never did by hand.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gib1507 Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2011 at 8:54pm
Excellent, thanks very much for that being a bit shall we say vague with mathematice especially division this'l help me quite a lot (wish i'd read this post yeserday though might have saved me from making scrap!!!! lol

no seriously many thanks a really helpful tip
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Claude Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2011 at 11:04pm
This is basic trigonometry, which can be quite daunting to the non-mathematician/engineer. It's called the principle of similar right triangles. You can read more here: http://www.tpub.com/math1/20a.htm particularly the practical explanation associated with figure 19.5. This is also explained in the Boy Scout Handbook in the chapter on measurement.
<rant> Most young people today are not taught anything beyond simple arithmetic because of "feel good" policies in schools and the lousy math skills of the teachers...</rant>

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Post Options Post Options   Thanks (0) Thanks(0)   Quote MC Black Quote  Post ReplyReply Direct Link To This Post Posted: 27 Oct 2015 at 12:12am
At primary schools, the teachers could  well be teaching the children something Mathematical that they don't really understand themselves.

I  hope that there are few secondary schools where Mathematics is  NOT taught by a specialist - somebody with a degree in a subject that requires a high level of numeracy (eg engineering, physics) if NOT Maths.

But if there's a shortage of skilled subject specialists, it's quite likely that the younger children will be taught by somebody with less understanding of the subject leaving the better qualified man to teach at Sixth Form level.

One year during my time as a schoolmaster, I  was loaned to the girls school next door to teach an A level Physics group and my bright fourteen year olds were taught Physics by a spare Biologist from next door.

While I  would  NOT dream of questioning her competence to teach third form Physics, she did NOT have the background knowledge to add value to the lessons by making them fun - so we probably lost a number of potential A level and university physics candidates that year.

Apparently one could  qualify as a primary school teacher without having an O level in Mathematics!!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote copeau12 Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jan 2017 at 12:04am
Great tip !
This is why maths are cool, in fact. ;)
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