[Gandalf_The_Gray]

I never cared much for Picket or K&E slide rules, they always felt "gritty" when you manipulated the slide and cursor. Most of my ME colleagues used 10" Post Versalog slide rules as did I. K&E and Picket were made of aluminum whereas Post used laminated bamboo. The bamboo had natural oils which made manipulating the slide as smooth as silk. I carried 5" and 10" Versalog slide rules until I bought an HP 45 calculator. I still keep both around. They do something the calculators don't and that is they don't conceal answers with 15 digits of false precision. Slide rules force you to put your data in "standard form" and cause you to think about the precision of your input. If you are working with data that is known to +/- 10% accuracy there is no point in calculating to 15 digit accuracy as your answer will be no better then +/- 10%.

They used to teach courses in "estimating", I suspect that is no longer true.

Regards,
GtG

PS There was one guy in my nomography and empirical equations class who had a 15 cycle circular slide rule. It had C & D scales in a circular track surrounding a spiral set of scales they were effectively some 20 feet long. The outer pair could calculate to five significant digits which you used to find which cycle to read on the inward spiral. There is always somebody like that in every math course!

[PUGACHEV]

My dad, who was a civil engineer, got an award from the Navy Department for inventing a type of circular slide rule for some sort of task the Navy had.

[conservatism_IS_compassion]

I bought a Dietzgen slide rule for $20 from the school store. I always regretted not spending the extra $10 it would have cost for a Post - but then, in my defense I did ask what was better about the Post. But it was foolish of me to ask a clerk in a school store (who in retrospect probably could not even multiply with a slide rule) instead of asking someone who actually used a Post slide rule.

My brother, who’s severely physically handicapped, used a circular slide rule. It had a pair of radial indicator lines whose angle represented the ratio between the two numbers to which the two were set. I really never learned how to use it . . .