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I Forge Iron

Reading a ruler, the other way


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Rulers are tools. So let us look at ways to use the imperial ruler.

If you have a measurement of 3-7/8 inches, to get there you measure 3 inches + 1/2 inch + 1/4 inch + 1/8 and then converted all that to 3-7/8 inches for the total measurement. 

To transfer that measurement to something else you break down 3-7/8 inches into 3 inches + 1/2 inch + 1/4 inch + 1/8 inch and make your mark. All this conversion and addition is what confuses many people.

There is a better way. DO NOT CONVERT. Keep the original measurements as they are. That is 3 inches + 1/2 inch + 1/4 inch + 1/8 inch then transferred to the work piece, and read directly on the ruler as 3 inches + 1/2 inch + 1/4 inch + 1/8  to make your mark. No math involved.

How do you find the half way point of that 3-7/8 inch measurement?  Fractions, with a large groan.

Follow me for a moment as it is really quite simple.

The original measurement was made as 3 inches + 1/2 inch + 1/4 inch + 1/8. So to get the halfway point you simply take half of each measurement. Half of 3 is 1-1/2. Half of 1/2 is 1/4. Half of 1/4 is 1/8. Half of 1/8 is 1/16. And there is your answer. To make your half way mark, it is simply 1-1/2 + 1/4 + 1/8 + 1/16 and mark.

All this becomes clear when you use it. You will catch yourself reading and converting. So read but do not convert.

There is an even a simpler way. You have been reading the ruler from left to right, to get 3-7/8 inches. The ruler can also be read from right to left, and you get 4 inches minus 1/8 inches, which brings you to exactly the same distance. The difference is 3+ or 4- when you read the scale. With just a little practice, and learning to say minus, you can speed up measurements and improve accuracy.   


Or go metric and just read the distance directly in units of 10.

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I've noticed that a lot of people never really grasp the notion that doubling the denominator in a fraction divides the quantity in half.  Tripling gets you a third, and so on.

Another super-quick way to get equal divisions using a straight ruler is to mark perpendicular lines at your end points.  Now take a ruler that's longer than the marked end points and set it diagonally across those perpendicular lines.  Tilt it until you arrive at a even or odd number which corresponds to easy division for your problem.  Let's say you've got a piece of stock that's 7-5/16" long and you want to divide that length into equal thirds.  Mark the 7-5/16" length with a perpendicular line at the origin and the end point.  Now take the rule and lay it diagonally until the zero and the 9" mark cross the origin and the end point line respectively.  Mark where the 3" and the 6" appear on the ruler.  Now take those points and pull down a perpendicular line from them.  The distance is perfectly divided into thirds with easy math.



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Or just go to Harbor Freight and get a "Center Point" 25' tape.  The upper side of the tape is marked as standard  inches and fractions, the bottom side shows inches and fractions but is at one half scale.  So measure the length, say 10 7/8".  Just look on the bottom side for 10 7/8"  and you have the center point of middle of your measurement.

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Stretch and mark a string to your distance. Then fold it and mark the folds, the # folds = a multiple of the # of desired divisions. It's the easiest way I know of to divide a cylinder, say the three air inlet slots in your Mikey burner. 

Worked to build pyramids, East and West, you know. For right angles you pull a 3,4,5 with a knotted cord and stakes. 

Soft wire and a sharp blade for precision work.

Ruler? Don't need no steenkeen ruler!

Frosty The Lucky.

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On 2/5/2019 at 11:25 AM, ThomasPowers said:

I showed my new student how to get a general halfway point on a piece of sq stock by balancing it on your finger.

Ike Doss showed me how to do that with an anvil hot cut. Balance it, hit to make a mark, heat it up and cut it.

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