Al Capwn

Tips to remove use of trivial math?

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8 hours ago, Llama said:

I will never for the life of me understand why people insist on thinking that metric is somehow better or easier. 

Which is easier to do in your head:

13mm - 7mm, or 33/64 - 9/32?

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8 hours ago, Llama said:

I will never for the life of me understand why people insist on thinking that metric is somehow better or easier. 

Because nothing is ever 49.7mm, its always 50. <=== Read Sarcasm Here!

 

2 minutes ago, Marmotjr said:

Which is easier to do in your head:

13mm - 7mm, or 33/64 - 9/32?

You mean 33 - 18.  Common denominators?  We all went to elementary school, right? :)  As many have said, this is a topic without a right answer.  I was a lousy math student but, I do what works for me.  Pick your method and rock on.

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What kinda boggles my mind, there have been a number of laws passed in the US since the mid 1800's detailing the usage of the metric system in the US.  In 1975 Ford signed the Metric Conversion Act which, paraphrasing, said the US should use the metric system for official and business use.  We can see how well that has gone. 

- http://www.us-metric.org/metric-system-laws-and-bills/

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It isn't not about right and wrong, and that was my point. If all measurement is arbitrary (ok most) then use a system with the smallest whole number values of consequence in order to simplify computation. 

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9 minutes ago, Marmotjr said:

Which is easier to do in your head:

13mm - 7mm, or 33/64 - 9/32?

I can't remember a time that I had to do that in woodworking. The time odd dimensions come up are when you're trying to put 7 drawers in a 20" opening. Which is really just simple math, but you'll end up with something "scary" like 9/32. By the way, your original math problem isn't apples to apples. 13.969 - 7.1438 is the equivalent. So, if you want to split hairs, I can too.

For the most part I think in decimal form. I rarely "see" dimensions in fractions unless it's a rough dimension. I'll say thing like "That's 1/2 an inch" but in my mind it's .500". Decimals also make the math easier, but most people seem to forget they exist.

For some reason people forget metric also uses decimals. Go look at your allen wrench set, see the 5.5mm one?

So what's easier for you? Let's take 1/8" for an easy example.

1/8" --> .125 --> 3.1750  - You're thinking, well, it's a little more than 3mm... 

I think the .125 is easiest...

When I worked as a machinist and saw a fraction, it meant it's a rough dimension or one with the least tolerance (usually for the saw cutters).

.125 means something real. It is precision in a short and understandable form. I get my size, and the tolerance all within one simple number.

Splitting hairs here, as woodworking rarely relies on such precision. It's usually some Norm measurement, 10 and a half strong... lol 

 

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I will avoid taking measurements whenever possible. Here's an example, I needed to build the exterior shell for my tool chest, so I made a couple of saddle squares using end grain off cuts (from the exterior shell material) and used those on the interior part to reference the cut:

587d3ef267cd7_2017-01-1610_48_01.thumb.jpg.e4345765ce171d900c0d4663fcd2ce18.jpg.ac8c69d6d355141c87dd1acc21b1b325.jpg

Then I used that reference to setup a stop on my miter saw:

587d3f03ee22d_2017-01-1610_50_22.thumb.jpg.ef74de321c4506de283f118506ca5128.jpg.6c8af7ee480bb4376229c48d36b02363.jpg

All parts fitted like a glove.

587e8961d7a74_2017-01-1718_07_35.thumb.jpg.d79696c844dbb882726f57d75bc5184d.jpg.342ec086eef9bd7bac2f882ed34ba41d.jpg

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9 hours ago, K Cooper said:

John, please explain the never measure a board width. 

If I want a board to be 12 5/16 wide I set my fence for 12 5/16 and that's what I get. No pulling tapes and making tick marks on the board and aligning the blade. In order to accurately set it up you need to first have an accurate tape on the saw, then I make 3 cuts at different widths and check with calipers. 

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8 minutes ago, Janello said:

No pulling tapes and making tick marks

Exactly. Machine setup is the most important part, which is why I don't understand why it isn't taken more seriously. You have to know how to work on your machines. I don't care if you can measure a piece to the nearest .001, if your machine can't cut it... it doesn't matter.

Also important is to have your pieces all the same. This makes life so much easier when working with properly milled stock, things just go easier. Making repeatable parts is almost impossible with crap machines or a crap setup.

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I'm more of a convert fraction to decimals.  I have tried metric, which in some cases is easier, but it adds an extra step.  What I mean by that is lets say I need to fit a cabinet in a certain space, by habit I measure in imperial, then I need to convert to metric.  Even measuring with metric tape, creates doubt because of the way my brain is wired.  

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47 minutes ago, Llama said:

...The time odd dimensions come up are when you're trying to put 7 drawers in a 20" opening. Which is really just simple math, but you'll end up with something "scary" like 9/32. ...

Using your example, would it be easier to use a pair of dividers and a sector?

 

Again, in certain applications, it is just "better" or at least more efficient to do the "hard" (really, basic) math, figure out what it is, set the table saw fence and cut it to size.

In regards to metric vs. everything else, that is like Mac vs PC - everyone has a favorite and some are passionate about one over the other. They are both numbering systems that have advantages and disadvantages. The irony is that no matter the number, 99% of the time, most people don't really care - it is just going to be plugged into the tablesaw or CNC and cut. 23 5/16th (or 592.1375mm), set fence, cut piece. It is when performing computation, which system, in that given equation is easier to solve?

To me the appeal of things like dividers and sectors is that the process is a constant, and works more in the realm of geometry and algebra rather than integer-based mathematics. It isn't that one is superior to the other, it is just my personal preference to remove as many variables that are easy to make mistakes. A / B = C vs. 27 / 7 = 3.85714285714

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Absolutely. My thinking was if I have drawer dividers, say 1/2" thickness, I have 6 of those. So that's 3" - 20" (opening) gives me 17" of actual drawer space. Divide by 6 and I get some silly 2.83" Which is a crazy number, but one I can work with. I know it's .008 larger than 2.75 (2 3/4).

 

You can get close in your head. Close enough to rethink the thickness of your dividers.

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10 hours ago, Llama said:

I will never for the life of me understand why people insist on thinking that metric is somehow better or easier. 

If the paper reports that the local dam will top out unless 1K acre feet of water are removed in the next week, then what outlet flow, in cubic feet per second will achieve that?

The Dam master has a table to help him with that.   

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2 hours ago, Marmotjr said:

minds me of the time I was teaching a coworker binary, and then other number bases.   I had hm count out loud in binary,

 

If you're trying to count on your fingers, you can get to 1023 by counting in binary ;-)

[Edit: I guess that assumes you are a SawStop user.)

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2 minutes ago, Pondhockey said:

[Edit: I guess that assumes you are a SawStop user.)

Or smart enough not to touch a moving blade. 

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@wtnhighlander - Ahh ok, I am presuming it works along the same principle as this router jig?

I would absolutely be interested in seeing your contraption!

Yep, same principle. Its a common tool, I just recorded myself making a quick one.

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On 5/16/2017 at 8:53 AM, Llama said:

I can't remember a time that I had to do that in woodworking. The time odd dimensions come up are when you're trying to put 7 drawers in a 20" opening. Which is really just simple math, but you'll end up with something "scary" like 9/32. By the way, your original math problem isn't apples to apples. 13.969 - 7.1438 is the equivalent. So, if you want to split hairs, I can too.

 

Your question wasn't "Why people think metric in woodworking is easier" but "Why do people think metric is easier".

My response was that 13-7 is easier than their imperial equivalent (not equal, I converted one way, you converted the other direction).  Decimal math is almost always easier than fractional.  It's one step, while in fractional, it's at least 2 (GCD and all that).  More steps equal more chances for error. 

But I use imperial all the time in woodworking, but immediately switch over to metric when doing any 3d design for printing (unless of course, it is something woodworking related).  It's because all our woodworking tools are in imperial.  My table saw doesn't even have metric.  All my forstner bits are imperial.  We buy 6/4 stock, or 3/4 ply.   Our brains are trained to think in imperial.  Without life long exposure, or prolonged practice, shifting one's paradigm to a new method is very difficult. 

International standards are there for our benefit.  There are left hand drive countries that have switched to right hand drive, because all of there adjoining neighbors were right hand drive.  The majority of remaining countries that are still left hand drive do so because they are islands, and there is no onus to switch.  Car companies hate trying to market vehicles in countries with opposite drive, as it forces them to have separate costly production lines.

Already the foot is based on the meter as it's standard, .3048 meters per foot.   There is no standard foot by itself.  It uses the carefully controlled standards already in place for the metric system. 

The US needs to switch over.  It won't be overnight though, can't be, this thread is proof of that.  It will take a couple generations.  Add km/h to speed limits, all rulers have both units, start marking drill bits in both sizes (that'll be fun *sic*), etc etc.  Eventually, as the imperial unit is phased out of normal life, people will barely notice as they have become accustom to thinking in both units. 

But the woodworkers and machinists of the US will have the hardest time.  "Old" tools will still be in imperial, and people will be loathe to retool their shops just for this.  Old machinery in factories and such will still require imperial tooling.

 TLDR; Anyways, metric is easier, but it's tough to think like that if you're not familiar with it.

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It's funny because I'm basically saying the same thing. Fractional math is inherently more prone to error. Mostly to it being inaccurate. As noted by my Norm comment.

 

The fact remains, if you use decimals (as I laid out in my post) both metric and imperial are easy math.

 

I've noticed a pattern with this debate over the years. It's the people that can't think in decimal form saying imperial is hard. Then the metric guys say, "look ma, no fractions... yay!" So you say, metric is easier because decimals. I say, all math is easier with decimals no matter which measuring stick you choose to use.

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31 minutes ago, Llama said:

It's funny because I'm basically saying the same thing. Fractional math is inherently more prone to error. Mostly to it being inaccurate. As noted by my Norm comment.

 

The fact remains, if you use decimals (as I laid out in my post) both metric and imperial are easy math.

 

I've noticed a pattern with this debate over the years. It's the people that can't think in decimal form saying imperial is hard. Then the metric guys say, "look ma, no fractions... yay!" So you say, metric is easier because decimals. I say, all math is easier with decimals no matter which measuring stick you choose to use.

There is one missing item. The mm and the inch are too dissimilar. If they were to make tapes in tenths of an inch, we could likely adjust...but why? The machinist is in tenths and thousandths all the time. This works well.The guy asked about removing trivial math. The mm is one of the finer whole number systems. It already exists. The half mm (read strong or weak) is likely the finest measuring we ever do. Pickier stuff is never measured but shaved and fitted. I never said better, but chose a practical simpler. Those tapes already exist. I won't bother myself because I don't measure all that much, but can see why someone might. 

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14 minutes ago, C Shaffer said:

The mm and the inch are too dissimilar. If they were to make tapes in tenths of an inch

Slightly disagree (splitting hairs)... The greatness of decimal math is it doesn't care. .100 is a tenth of an inch. And .125 is an eighth. 

My point is that neither system is more accurate that another, or easier to use than another when using decimals. It is all simple math that most people over 12 should be able to do in their heads.

In woodworking you need parts to be the same thickness, who cares what the scale is? I should build something using the thickness of a pencil just to prove a point. My rails and stiles will be two pencils thick, and 5 pencils wide. The case will be 500 pencils high, by 350 pencils wide. The unit doesn't matter. And besides, measuring is the enemy to precision. (By the way, I have no idea what size that would be... I am guessing that there are four or five pencils are around an inch) 

Now I need a bunch of pencils. :) 

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2 hours ago, Llama said:

Slightly disagree (splitting hairs)... The greatness of decimal math is it doesn't care. .100 is a tenth of an inch. And .125 is an eighth. 

My point is that neither system is more accurate that another, or easier to use than another when using decimals. It is all simple math that most people over 12 should be able to do in their heads.

In woodworking you need parts to be the same thickness, who cares what the scale is? I should build something using the thickness of a pencil just to prove a point. My rails and stiles will be two pencils thick, and 5 pencils wide. The case will be 500 pencils high, by 350 pencils wide. The unit doesn't matter. And besides, measuring is the enemy to precision. (By the way, I have no idea what size that would be... I am guessing that there are four or five pencils are around an inch) 

Now I need a bunch of pencils. :) 

Again, your point has little merit. There is no practicality in inventing a new system. This got into the weeds with people misinterpreting that continually. The metric tape already exists in that base ten profile that agrees with decimals. The conversation should only be about measured pieces like those to fit a recess. The fastest and cheapest way away from converting 16ths to decimals etc is to use what already exists. 

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Agreed. Decimals already exist. No need for any conversion.

 

 

Sent from my iPhone using Tapatalk

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I use both metric and imperial.  I use imperial for large measurements, such as "this cabinet is 48" wide" and use metric for laying out joinery.    Works for me.  I do wish I was raised in metric because I find it to be more useful, but it is not intuitive to me.  I can visualize 12" but I have a hard time visualizing 30.5cm without converting back to inches first.

 

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By the way, no need to invent a new system. Agreed... just showing you (and anyone else) how dumb the entire argument is against one or the other pertaining to woodworking.

 

 

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BTW @Llama, I love the weeds and splitting of hairs. I think I did a bad job of articulating in the first place leaving the weeds as a distraction. If I thought I could rewrite my first post without offending I would. 

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