With all these new power tools, why do we still measure in the dark ages?

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Blog entry by technicallymark posted 04-08-2010 08:27 AM 2267 reads 0 times favorited 51 comments Add to Favorites Watch

Quick, which is bigger, 5/16th or 11/32nd? Having trouble? Try this. Which one is bigger 10 or 12? Easy right? I’m all about easy and trying to remember how to convert fractions isn’t really something I want my brain working on with spinning sharp blades around.

I’m not sure why we can’t be like the rest of the world and use “metric” for measuring, but it would make life a little easier in the shop. I might be a little biased since I have formal education in biological science, but the company I work for makes machinery where all measurements are based in metric. Since I’ve really just begun on my woodworking journey, I have not yet invested in a good metric tape measure, but I do have a 300 millimeter ruler with a great straight edge that is handy and reliable.

On that same ruler, if I’m measuring from zero to say 10 and 5/16th inches, the ruler just isn’t marked for that kind of accuracy. Yeah, I know most people probably only measure to an 1/8th, but if you make smaller projects, smaller increments just might come in handy. So if you’re shaking your head yelling at me about how difficult the metric system is and its just a waste of time, I have a few tips that might just get you started thinking metrically, which will eliminate all those annoying fractional conversions swimming in your head.

Rule 1: One inch is 25.4 millimeters or 2.54 centimeters. Measuring in millimeters is actually more convenient when talking about a 4” board which is really just 102.0 mm. Your blade if you have an average table saw is 254.0 mm(10 inches).

Rule 2: Converting from fractions can be done but its not very fun. Take 11/16ths. If we do the math on that fraction we get 0.6875 inches(I love decimals). Now you simply multiply 25.4 mm(again it equals one inch) with the number your calculator gave you when you punched in the fraction. So the big conversion is 11/16ths is equal to 17.4625mm. Unless you use a pocket microscope, you probably won’t be able to tell the difference between 17.4625 and 17.4999, and it really doesn’t matter. I’ve found my eye can differentiate at most a 0.1 to 0.3 mm difference in measuring an object on paper.

Maybe I’m just angry towards my grade school teachers who told us all of the US would be metric by the time I graduated from high school. The only metric that has seemed to stick since 1985 is a 2L(liter) of soda in a bottle. I think wine and liquor are measured in milliliters but I don’t drink much other than beer.

Standard ruler<ahref>Metric ruler

My next project is a mobile base for my contractor’s saw with some storage in it. Here are the standard SAE dimensions that I want it to be. 24 inches wide, 32 inches long, and 21 inches high. But I think I’ll work on bringing my work brain into the shop. I’ll make it 610mm wide, 813 mm long, and 533 mm high. And I’ll add 51mm high casters with locks on two of them.

The ply from the lumber yard is 23/32nd, or almost 3/4 inches. But really, its 18.3 mm(rounded up) thick. I’ve seen other ply marked as 12mm without any fractional dimensions. What could that be in inches? Well, 12 is almost half of 25.4, which we know is one inch, so indeed, it was 1/2 inch ply.

Look at the rulers below and tell me which one is easier to read? I quickly did a search and found Lufkin makes a nice looking tape measure with the primary marking metric, which is probably what most of us use when we measure something left to right. Let me know if you hate or love the metric system or even if you are considering warming up to the idea.

-- Love the taste of sawdust in the morning!

51 comments so far

View David Craig's profile

David Craig

2137 posts in 4162 days

#1 posted 04-08-2010 10:25 AM

I like the idea of the metic system and agree that it would make life for a woodworker much easier, except…

I would have to perform constant metic/SAE conversions because almost all my router bits, saw blades, set up blocks, etc. are geared towards SAE measurements. When I buy lumber, it is in board or linear feet, most of my woodworking plans I have at my house would require me to convert to metic, etc. etc. etc.

I agree that decimals are the way to go and would quickly go that route if all had to replace was my tape measure. Just too many items in my available market and my existing inventory are SAE based. When the road to simplicity is filled with complexity, I tend to avoid that path.

Great food for thought. Thank you for posting.


-- There is little that is simple when it comes to making a simple box.

View Abbott's profile


2570 posts in 4357 days

#2 posted 04-08-2010 10:33 AM

I’m happy to let the metric system stay far away from me for as long as possible. I don’t want it or need it. As far as I’m concerned there is to much of it around all ready.

-- Ohh mann...pancakes and boobies...I'll bet that's what Heaven is like! ♣ ♣ ♣ ♣

View Tony_S's profile


1458 posts in 4136 days

#3 posted 04-08-2010 12:34 PM

Canada has been officially Metric for the better part of 35 years now….and for the most part, it is. There are a few trades that are stuck on SAE though, carpentry being on of them. It is slowly dying out though(with the ‘newer’ generation slowly taking over). Even the construction industry is split though. Residential construction is still ‘almost’ purely SAE, commercial construction IS PURELY Metric….so I get to deal with both on a daily basis.

Metric is MUCH more simple, (everything is divisible by, or in multiples of 10) and there are FAR fewer mistakes with the metric system. Anyone who tells you differently is simply stubborn, bullheaded, and doesn’t like change.

-- “Wise men speak because they have something to say; fools because they have to say something.” – Plato

View Moron's profile


5048 posts in 4946 days

#4 posted 04-08-2010 12:40 PM

nothing is stopping anyone from using the metric system

-- "Good artists borrow, great artists steal”…..Picasso

View Dick, & Barb Cain's profile

Dick, & Barb Cain

8693 posts in 5353 days

#5 posted 04-08-2010 01:31 PM

I Agree.

Here’s a video about the metric system in the USA.

-- -** You are never to old to set another goal or to dream a new dream ****************** Dick, & Barb Cain, Hibbing, MN.

View bunkie's profile


415 posts in 4200 days

#6 posted 04-08-2010 01:40 PM

Let me be the dissenter here. The real issue with decimal measuring systems is that at some point the next significant decimal place results in something that’s too small to see.

For example, we can (hopefully) all see one millimeter (about the thickness of a US dime). But how many of us can visually resolve .1 millimeter? For me, that’s the issue. I’m stuck with the smallest gradation that I can see (1mm) being too large to get the necessary level of precision. I can’t remember ever seeing a rule with .1mm gradations.

Fractional systems are far better at this as one can always literally “split the difference”. Yes, fractions are a bear. But, in my opinion, that’s a fair price to pay.

It’s all about Zeno’s Paradox…

-- Altruism is, ultimately, self-serving

View jerryz's profile


164 posts in 4332 days

#7 posted 04-08-2010 01:42 PM

Well, Skarp makes a valid point of why the fractional system is useful in woodworking, however I take you to task for the way you set up the question, in order to make the comparison you ask which is bigger 10 or 12 and compare that to 11/32 vs 5/16.

so let’s make that comparison more honest shall we? what is bigger 11/32 or 10/32

Now lets use the metric system shall we?

What is bigger? 8.78205 or 7.93750 when you need to go make a cut try to remember that number, good luck with that!

Let’s ask around what is easier…..By the way I grew up using 100% the metric system and only discovered the Imperial system as a result of my woodworking endeavours….

View JohnnyW's profile


83 posts in 4084 days

#8 posted 04-08-2010 02:09 PM

I’m English, so naturally I was bought up using the metric system!. I’m a design engineer, so I have to use it all day, every day. It’s easy, but it’s boring.

In the English system, most units are built from 8 or 12 or 3 smaller ones; in the metric system, they’re built from 1000. I can visualise 3 feet making a yard, but I can’t visualise 1000 of anything.

In the English system, we used names like mile, furlong and pound; in the metric system we have decagram and kilometer.

I can use metric numbers efficiently, but I can use English units for pleasure. Stick to English.

-- John

View Craftsman on the lake's profile

Craftsman on the lake

3813 posts in 4491 days

#9 posted 04-08-2010 02:28 PM

What is sad is that he metric system was developed to make things easier. In fact you can’t do most science without it. Relationships for science in metric are by plan. For example. If you have one cubic centimeter of water, it will have a mass (weight) of 1 gram. And it will also have a liquid volume of 1 mililiter. And it will take one calorie to raise it’s temperature one degree centigrade. Not only that but an object that size if it weighs less than one gram will float and more than one gram will sink. So, it’s not only easier to read the ruler and do the math but relationships in metrics are needed to do any science. That’s why kids have to learn it in school when science begins to have some math to it. It’s also a handicap for students in American science. They have to learn a new language before they can continue. Try finding simple relationships between ounces and inches, and degrees F in the American (standard) system of measurement!

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View canadianchips's profile


2632 posts in 4050 days

#10 posted 04-08-2010 02:56 PM

Yep .I am canadiian, (name is the clue that gave it away). WE do have metric and we have IMPERIAL measurement. The largest PROBLEM occurs when people try to cinvert. MISTAKES are made. If you want to build something in metric, use the metric tape measure. You want decimal points you can have them. You cn take ANY fraction and turn it into decimal point. TOP numberr divided by BOTTOM number. 3/8 inch = .375 etc,etc. We drive car down a road that was surveyed in imperial. Land was surveyed in imperial. Got off track of woodworking here. Plywood companies still make 4ft x 8ft sheets. When you frame a wall using 16inch or 24 inch O.C. it works out well. The change in THCKNESS has been a pain ! 3/4 thick plywood is called 19mm.
19mm is thicker than 3/4 inch. Now my dado blades don’t work well. To make a long story short. DONT waste money changing to metric now ! Avoid converting – opportunity for more mistakes. I am open minded, BUT I personally enjoy building in inches,& feet,

-- "My mission in life - make everyone smile !"

View NewPickeringWdWrkr's profile


338 posts in 4066 days

#11 posted 04-08-2010 03:17 PM

Craftsman has it right. The math of the metric system is easy. 1 unit = 10 deci-units = 100 centi-units = 1000 mili-units. 1 unit also = 0.1 deca-units = 0.01 hecto-units = 0.001 kilo-units. It doesn’t matter if it’s 2 dimensional (metres) or 3 dimensional (litres) or mass (grams).

But the difficulty in industry is that it’s expensive to convert to a truely metric system if already established in imperial methods. A can of coke is 355mL. Why? Because the dies that stamp out the can were originally built to 1.5 cup specifications. The conveyors that move the can, the dispensors that fill the can and the packaging that holds the cans etc. can’t be converted to a 350 mL or 400 mL can without overhauling the whole system. What they can do is change the labling! Canada is operating on a metric system as Tony_S mentions above, but that only became law in Canada in the 1970’s.

I grew up on the metric system, but had to learn the imperial (US) as well as the imperial (UK) (that’s another rant for another thread – UK or US gallons ARRRGH!) system going into construction with my dad and I discovered recently in beginning to draw plans that the system really lends well to diverse ways to scale your drawing.

I prefer the metric system, but find it easier with current tools and materials to use the imperial (US) so long as I don’t start getting into hands, furlongs and chains or stone.

I wait for the day that metric is more popular than imperial

-- Mike - Antero's Urban Wood Designs

View TwistedRedneck's profile


41 posts in 4545 days

#12 posted 04-08-2010 03:17 PM

I remember the topic or idea was brought up in the past and the last big push for the Metric system in the USA was shot down. Mostly by the larger manufacturing companies I believe. Cost too much to switch over to Metric.

Dont get me wrong, I am not against other countries or what they have but I am American. I like my difference from the other countries. I like my measurement system and hate the Metric system. To me the ruler on the left is easier to read and yes, a constant conversion would have to be going on to figure out what the actual size is.

My wife is German and they use the Metric System and when she starts telling me the size of something, my mind shuts off and goes into spin cycle. Tell me the measurement in something I understand.

Not much of a Metric fan myself.

-- Nails are better wood fasteners than screws, if both are applied using a hammer.

View b2rtch's profile


4921 posts in 4101 days

#13 posted 04-08-2010 03:32 PM

Amen and Amen.
Being raised”metric” using inches and fractions is a nightmare.
What really gets to me also is the wire gauge sizes , the smaller the number , the bigger the wire! How ever thought of that?
What about 1/2” pipe which not 1/2” in anyway or 1/2 ply wood which is not 1/2” either and 2×4 and board feet and so on.
What a screwed up and out dated system!

TwistedRedneck which part of the metric system don’t you understand?
DO you understand the you have 10 cents in a dime and 10 dime in a dollars ,which is to say that you have 100 cents in the dollars. If you can understand that, I am sure that you do, then you understand the metric system.
What about metric inches that i USE AT WORK, HOW DO YOU LIKE THAT?. What about bolts that GM uses, the head is metric but the screw itself is standard, wonderful no!

-- Bert

View ChuckV's profile


3370 posts in 4580 days

#14 posted 04-08-2010 03:32 PM

As canadianchips says, the big problem is converting between systems. It is similar to learning a second language. It seems next to impossible if you keep translating back and forth between the new language and the one you are more familiar with. Then at some point, you start thinking in the new language, and it is a real breakthrough.

That said, I am very comfortable working with the arcane system of inches and cubits in the workshop. I know what 1/16” looks like. I have a digital caliper that displays measurements in either millimeters, decimal inches or fractional inches. I find that I almost always use it in the fractional inch mode. If I want my board to be 3/4” thick and it measures 13/16”, I crank the planer wheel down one revolution and I am set. I know that this is because the machines are set up that way, but the machines are set up that way :-)

-- "Join the chorus if you can. It'll make of you an honest man." - I. Anderson

View cbMerlin's profile


100 posts in 4474 days

#15 posted 04-08-2010 03:39 PM

Huh. This sort of jogged my memory. I remember being told by a teacher, in about the 4th grade, that by the time I graduated from high school, everything would be metric. That was over 40 years ago. For some reason, I don’t struggle with fractions, feet, yards, etc. Metric, well….? I know you can get soda in a 2 liter bottle. I know what a 100 yard dash is, but still can’t tell you if a 100 meter dash is shorter or longer. I remember running the “440”, the “880” and the mile in high school track, and just assume the 400m or the 800m is sorta the same. I always carry my tape when I go to the lumber yard in case something is listed in metric. I have a set of metric wrenches & sockets cause I frequently run into stuff that SAE won’t work exactly right on. I havn’t purchase a ratchet in a long time, are they still 1/4”, 3/8”, 1/2”, etc., or have they changed too? By the way, a 2×4 isn’t really 2”x4” and half inch plywood isn’t always a 1/2” thick, so what the heck does it all matter anyway? LJ’s, like Marines, “adapt, improvise and overcome” anyway, so the industry can do what they want, we’ll still make it work! I say “LJ’s for president!”, if they can’t do it, it can’t be done!

-- Sawdust looks better in the garage than cars, explain that to your wife!

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