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Fractions Simplified
Tip# 3324 By Mark Kenyon On 31-Jan-2010
Rated By 1 users
Categories : 2D Operations
Software type : AutoCAD 2010
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Check out this tip when trying to offset a hole from the centerline.

Mark T. Kenyon, who uses AutoCAD in his job in the oil and gas industry, expands on a tip published previously with this tip that explains how to convert object measurements from fractions of inches to a decimal format.

"When working in decimals, it is very easy to remember simple fractions like .500 for 1/2", .75 for 3/4", etc. However, how many of us can remember the decimal equivalent for 23/64" without pulling out the calculator or a decimal equivalent chart? Instead, you can key in the fraction as is; as long as the values are whole numbers, AutoCAD will do the math for you. This comes in handy when trying to offset a hole from the centerline (among other uses). No mental math, calculator, or special formula required — just value A over value B. Now if we could get Autodesk to enhance it further and allow the same technique to work with numbers that include decimal points, we would have it made — for example, converting millimeters on the fly and being able to key in 2489/25.4 to get the decimal equivalent in inches."

Notes from Cadalyst Tip Patrol: This technique is a real time-saver, with many possible applications. For example, if you are working in feet and you need to draw a line 8" in length, you can draw it as 8/12. You can also use this method to scale objects if their values include a decimal. In the example given in the tip (converting 2489 millimeters to inches), multiply both numbers by 10 and enter 24890/254. The problem is that your object would be 10 times too big, so scale it again by 1/10. There is an extra step here, but you don't have to do the math yourself, and you can key this in along with the Scale command very quickly.


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User comments
Comment by Gardiner,Ken
Posted on 2010-02-01 15:24:30
The illustration given by the Tip Patrol is incorrect. The object would not be 10 times as big since both numerator and denominator is multiplied by 10. It would be the same size.
Comment by McSwain,R.K.
Posted on 2010-02-01 15:44:11
I was going to say just remove the decimal point if needed, but CTP beat me to it.., and as Ken said, since the ratio would be the same, it will work fine without further scaling.
Comment by Gesner,Rusty
Posted on 2010-02-01 19:30:03
Actually, with a bit of simple AutoLISP formatting, you can enter all kinds of mathematical expressions, like: Command: l LINE Specify first point: Specify next point or [Undo]: (* 4 12 (/ 78 2)) 1872 But the QUICKCALC command/dialog is probably easier ;)
Comment by Hollingsworth,Michael
Posted on 2010-02-02 08:19:55
You could also enter (* 10 (/ 2489 254)), but that's slightly more work than 24890/254, and gives the same result. So let's use Occam's Razor here and keep it simple. ^¿^