Worldway

Proportional Dividers

37 posts in this topic

I might add a couple comments about the way I measured the planking problem I showed above.

The length of the two openings (4.85 and 4.00 inches) was measured by using a piece of stiff paper. You can see that in the photograph. These dimensions were used in the calculation. 

The width of the planks was measure with a dial set of calipers (with a dial indicator) that is accurate to within 0.001 inch.
post-246-0-51940900-1486065717.jpg

There is no way that you can be that accurate with the proportional dividers.

To pace off sets of repetitive dimensions on a chart it is cheaper and easier to use a simple pair of dividers:post-246-0-15033200-1486065455.jpg

 

jud, mtaylor and Canute like this

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Tools are tools, which to use is a mater of preference, confidence, knowledge and the availability of tools to choose from. I may choose to measurement using cubits, 'IE 14.7 cubits, the .7 being an eyeball best guess', and a slide rule for the math or a calculator if I need to measure that result somewhere using a measuring device marked in meters. I prefer to work in decimals, decimal feet unless I need decimal inches, you will find lots of little pencil marks around my fabrication projects. I may measure using a decimal scale with 10, 10 or a thousand divisions regardless of scale, imperial or metric, scales are a simple conversions, divisions are visible things that create refinement in the eyeball reading of a measuring tool and are the single most used method of refinement in any measurement until needing to think about technique to avoid repetitive and cumulative errors. Wife was an inch, foot girl, a defect in her early potty training, had to rid the place of such marked measuring devices, until the lesson was absorbed with comfort, that the end of fractions did not destroy her world, only requirement, was to be aware of the division, inches or decimal feet, I have pocket tapes with both, amazingly the foot marks are common, not double. Why pick on the wife? She wanted, and did help me in my work, Inches were a problem in a decimal world.

Canute and Modeler12 like this

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I've had a set of proportional dividers since my drafting days.  I look at them once in a while.  Never use.  If I need to resize a plan I find it much easier to have it scanned in and reprinted. 

 

Bob

donrobinson, druxey, mtaylor and 1 other like this

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So I won the Ebay auction and have the proportional dividers heading my way.  I paid a lot more than I should have but I realized the cost of buying new ones was very expensive.  They are made by Dietzgen so I know they are quality.  Hopefully I can put them to good use.

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It is interesting to see the two sides of this 'coin'.
If you have used the proportional dividers for a long time, I can appreciate that you like them for various reasons.
In my case, I have a pair and seldom use them, but so be it.
When Jud mentioned his liking for the decimal system (rather than fractions, I suppose) I agree. But when he talks about using a slide-rule - - - - I have to grin because those are dinosaurs in my college collection. Slide-rules are as accurate as proportional dividers and even more difficult to use and understand (I know Jud, you add or subtract logarithmic values, etc.).

The upshot is: if you like the tool you have, use it. If you want accuracy, calculate.

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