Most slide rules will do many operations, but the basic operation is multiplication.
Multiplication on a slide rule works because you can turn multiplication into addition with
X * Y = 10 ^ (log(X) + log(Y))
(Edit: i had e and ln up here, but 10 and log is a better match the slide rules from 1 to 10l
The rules are log scaled, so you find X on one rule and line up 1 on the other rule, then look at what number on the first rule is where Y is on the second rule.
Run a couple examples you know the answer to, and you'll get it. As I recall, wrapping/bounding is tricky, you might need to reverse X and Y or go the opposite way to get your answer.
You'll need to do it like scientific notation as well, the rules only have numbers between 1 and 10.
Division is inverted multiplication, so for X / Y, line up the rules so X and Y match, the quotient is what is on the X rule where Y is 1.
I don't know much about woodworking, are you doing multiplication or division with fractions, or adding? Do you want fractional results or decimals?
A lot of woodworking is done in inches and fractions of inches. Doing joinery where you have to consider things like the kerf of the blade often requires many annoying additions and subtractions of power-of-two denominators. While adding 3/16 and 5/32 is trivial, trying to do that while focusing on making a good cut and taking accurate measurements can be distracting.
Usually adding and division. For example "7 3/4 plus 8 1/8" or "15 3/4 divided by 4." Fractional result would be ideal. I don't know if a sliderule is a good tool for this is or not :)
You'll still need to do the addition, and then you'd need to eyeball 15 3/4 as a number between 1 and 2, do the division, and then eyeball the result into a fraction.
I think I've only seen decimal marked slide rules, you could certainly have a fraction marked rule, but it wouldn't be that helpful, because 15 3/4 is not easy to turn into
10 * (1 + 1/2 + 3/4 * 1/5 )
And then you're not at a power of two fraction anymore either. Some other tool would be better; probably a pocket calculator that's taken advantage of half a century of computational advances and can manage fractions.
Yeah, there's a ton of perfectly good fractional calculator apps and so on out there. I was just looking for an excuse to use my dad's old thing. Thanks again for the explanations.
No. A slide rule is all scientific notation (2 or 3 significant digits on the rule and you carry the mantissa in your head). Very good for accuracy but not so much for precision.
Comments
Most slide rules will do many operations, but the basic operation is multiplication.
Multiplication on a slide rule works because you can turn multiplication into addition with
(Edit: i had e and ln up here, but 10 and log is a better match the slide rules from 1 to 10lThe rules are log scaled, so you find X on one rule and line up 1 on the other rule, then look at what number on the first rule is where Y is on the second rule.
Run a couple examples you know the answer to, and you'll get it. As I recall, wrapping/bounding is tricky, you might need to reverse X and Y or go the opposite way to get your answer.
You'll need to do it like scientific notation as well, the rules only have numbers between 1 and 10.
Division is inverted multiplication, so for X / Y, line up the rules so X and Y match, the quotient is what is on the X rule where Y is 1.
I don't know much about woodworking, are you doing multiplication or division with fractions, or adding? Do you want fractional results or decimals?
A lot of woodworking is done in inches and fractions of inches. Doing joinery where you have to consider things like the kerf of the blade often requires many annoying additions and subtractions of power-of-two denominators. While adding 3/16 and 5/32 is trivial, trying to do that while focusing on making a good cut and taking accurate measurements can be distracting.
Thanks!
Usually adding and division. For example "7 3/4 plus 8 1/8" or "15 3/4 divided by 4." Fractional result would be ideal. I don't know if a sliderule is a good tool for this is or not :)
I think a slide rule isn't going to help much...
You'll still need to do the addition, and then you'd need to eyeball 15 3/4 as a number between 1 and 2, do the division, and then eyeball the result into a fraction.
I think I've only seen decimal marked slide rules, you could certainly have a fraction marked rule, but it wouldn't be that helpful, because 15 3/4 is not easy to turn into
10 * (1 + 1/2 + 3/4 * 1/5 )
And then you're not at a power of two fraction anymore either. Some other tool would be better; probably a pocket calculator that's taken advantage of half a century of computational advances and can manage fractions.
Yeah, there's a ton of perfectly good fractional calculator apps and so on out there. I was just looking for an excuse to use my dad's old thing. Thanks again for the explanations.
No. A slide rule is all scientific notation (2 or 3 significant digits on the rule and you carry the mantissa in your head). Very good for accuracy but not so much for precision.