Old School Tools

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Ever wish there was an easy way to quickly convert from one unit of measurement to another? Sure, today you can whip out your handy phone/calculator/camera/flashlight/etc. and do a quick calculation, but that level of technology has not always been available.  Instead, there were really clever cardboard converter tools.  Unlike a nomograph (where the numbers stay still and you move a straight edge over the page to find your answers), these sliding converters let you slide the numbers around inside a frame to get what you needed.  We have several examples here, courtesy of Paul!

OKI Electronics Measurement Converter

Hughes Microwave Calculator

Hughes Millimeter Wave System Calculator

M/A-COM VSWR Calculator

Screw and Thread Sizes from Lufkin Tools

Here's an example of the frame of a "Measurement Converter" from OKI Electronics of America, followed by an inside look at the inside piece (the bit that slides around).

OKI Electronics of America Measurement Converter

Here's what it looks like when you put them together.


So how does it work?  Say, for example, you get a measurement that for whatever reason shows up in rods (well, it's better than cubits). Simply slide the inside piece until "Rod" has a one next to it, and voila!  All the conversion factors are listed right there.

Kind of simplistic, sure, but handy nonetheless.  And some of these old slide charts had much more complex numbers on them - take a look at the Microwave Calculator from Hughes (1988):

They made one for millimeter waves, too (1975)!

VSWR Calculator from M/A-COM (1983)

Screw and Thread sizes from Lufkin Tools, 1935



Thank you to Paul for the generous loan of all of these converters!


Source : The archives of Paul Chorney