gift idea - kitchen rule #1: drawing the scale

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Blog entry by Sylvain posted 08-12-2021 04:44 PM 434 reads 0 times favorited 0 comments Add to Favorites Watch
no previous part Part 1 of gift idea - kitchen rule series Part 2: scale glue-up - first try and usage example »

My apologies for misplacing the real #1 of this serie in a forum.

see here for the very #1.

and where the idea comes from

Having done this:

I had to draw a scale for it.

First the principle.
Multiplications and divisions are done on a slide rule by adding or subtracting the corresponding logarithm.

The original scale goes from 1/8 to 12.

I wanted a scale going from 0.1 to 12.
log(0.1)= -1
log(1)= 0
Which make a span of 2.079 with the zero more or less in the middle.
I decided to multiply the log numbers by 130 which gives me a scale length of 270.27 (mm in my case but one can use inches).
Similarly, If I wanted a scale of approximately 12”, I would multiply by 5.8 giving a 12.06” scale length.
So I used a spreadsheet to make all the calculus:
- first column: the numbers for which I want a mark;
- second column: the log of the numbers in the first column:
- third column: the result of the second column multiplied by 130;
This gives me the distances from the point corresponding to 1 which means working with negative values for marks <1.
I have used the draw feature in the open office suite. As the zero is placed by default at the left margin of the paper blade, it was necessary to add 130 to all the values in the third column; so I made a fourth column in the spreadsheet which add 130 to the third column.
The draw programme has a snap to grid feature which ensure the marks are vertical and then, when drawed with the mouse, they can be anchored to a precise value. The positioning is made at a 0.1 mm but … the mark width is 0.1 mm.

Not having ever used this programme, I nearly needed 2 days to draw the scale while building the scale in wood took me max 2 hours.

-- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn (and that is nice)

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