Imperial or Metric?

[Robb White]

I have decided to get into woodworking and have acquired a number of tools and about to start buying woodpecker measuring devices 1281 square, 32" t-square and perhaps a story stick. The question is should I get imperial or metric? I have some green koolaid with plans for some more. The plan is to turn our formal living room into a library with built-ins, built-in master closet, amour, wood panel ceiling with recessed lighting and multi tiered out door decking. Haven't played with fraction much since school and wondering if going metric would be easier. Any thoughts? Thanks.

-Rob

[Judson Green]

Someone here, I forgot who, said one of the great things about imperial is its easy to divide in half.

[John TenEyck]

You'll make far fewer mistakes in metric. For whatever combination of reasons, however, I still work in imperial units - and I'm sure I make more mistakes because of it. A sort of compromise approach would be to use decimal inches.

John

[Kent A Bathurst]

You'll make far fewer mistakes in metric. For whatever combination of reasons, however, I still work in imperial units - and I'm sure I make more mistakes because of it. A sort of compromise approach would be to use decimal inches.

John

I am the exact opposite.

All my machinery is setup to read imperial - I would go nuts [I know - that horse left the barn a long time ago] in metric.

Plus - my soap box here - I have starrett analog dial calipers. Each "tick" on that dial face corresponds prciesly to a "tick" on my TS, my Biese CMS tables, the PC routers, etc.

[glenn bradley]

After a career of 30-odd years in octal, decimal and hex I escape to the warm embrace of imperial measurements in the shop to decompress. Fractions must use different pathways in the brain because my shop time is like deep meditation for me ;-)
That being said, I use both when I need to and being from the generation that experienced the move to and then away from metric I am comfortable with either.

[Wade Lippman]

Metric is so so so much easier to use. Try subtracting 2 15/16 from 9 3/32, or dividing 8 7/16 into thirds.
It would be wonderful if the US could go metric. Imagine one set of wrenches, and nuts always fitting bolts...

Sadly, I still use Imperial 80% of the time. Maybe I should bit the bullet and buy new measures.

[John Coloccia]

I would stick to imperial because that's what's easily, locally available for bits and things like that. That's what you'll find for markings on most US machinery. That said, there's no reason to use fractions just because you're measuring in inches, and there's no reason to use decimals just because you're measuring in meters. Imperial has an advantage in this regard as measuring devices in both decimal and fraction are commonly available, and you're free to use whatever is most appropriate for the situation. My favorite combination is 16R (aircraft ruled) gradautions...1/32, 1/64, 1/50 and 1/100 on the same rule. 50ths don't seem useful if you think of them like that, but if you think of it as .02", .04", .06", .08", then it's suddenly very useful and much easier to read than 1/100 if you don't need that precision.

Judson, I believe I've made the point many times that dividing by powers of 2 in fractional measure is trivial, and it's something we do all the time. Dividing something in half, is probably my most common math operation in the shop. Midpoints, router bushings, setting up a fence for a router, etc, all have that operation, and it's much easier to do it using fractions.

But most of the time, I'm working with decimal measure because that's most convenient for me. Stuck to my bandsaw are a couple of charts for freely converting between fractional inches, decimal inches, all the various letter and number drills, and all the metric equivalents. It's pretty trivial for me to work in whatever measurements are most convenient. Since I use a lot of hardware that's a mix of imperial and metric measurements, I don't really have a choice.

I also happen to think that the inch is a more convenient unit for basic woodworking. Centimeters and millimeters are too small, meters are too big, and no one actually uses decameters. Ditto for recipes in the kitchen. Ever try remembering a metric recipe. 180ml of that, 30g of this, 80ml of something else, etc etc. It's much easier to deal with 2 cups of this, 1 tblspn of that, etc. Just my opinion, but when I'm working in metric, I end up with lots of big numbers floating around, and converting to meters does no good because I still have to carry around the same number of digits of precision. Feet and inches just seem to work better for me to keep numbers small and manageable. Again, that's just my opinion.

Personally, I think metric measurements would be far more convenient for woodworking if fractional metric rules and tapes were more commonly available, and if things didn't jump from tiny little centimeters to gigantic meters.

Just to reiterate the point: Imperial does NOT imply fractions. You may use fraction OR decimal measure as you wish, and practically every common measuring device you might use is available as both.

[Chris Padilla]

I would say to get used to working in both. One little tidbit I picked up was that 1/32" and 1 mm are about the same so if you get used to working in one thirty-seconds of an inch, moving over or thinking in millimeters isn't that much of a change. The difference is less than 1 mil or 0.001 inch (1 mm is larger than 1/32" by 0.00081"). And unless you work in MDF all the time, you're sheet good thickness is going to be some integer of 1/32". I am slowly buying metric equivalents of just about everything in my shop these days. I picked up a '6 inch' metal metric ruler. I have a nice set of metric brad-point bits to complement my imperial set--both from Lee Valley. I recently picked up a set of metric center punches, too.

Finally, I think it is good for the brain to exercise your ability to add and subtract and divide and multiply mixed fractions.

And to John above, how about decimeters? 1 dm is about 4".

[David L Morse]

.. One little tidbit I picked up was that 1/32" and 1 mm are about the same so if you get used to working in one thirty-seconds of an inch, moving over or thinking in millimeters isn't that much of a change. The difference is less than 1 mil or 0.001 inch (1 mm is larger than 1/32" by 0.00081)...

Well, not exactly. The difference is actually ten times that. 1mm = 1/25.4" = .03937", 1/32" = .03125", .03937"-.03125" = .00812". That's 8mil not 1ml. Perhaps you're thinking of the fact that 4mm is within a little over 1mil of 5/32"?

I too am comfortable working in both systems. For example, anything that ends up in the barn is imperial and anything involving drawer slides is metric. (Not sure what I'll do if I have to build something for the barn with drawers.) As far as the kitchen is concerned it's easy to remember that 1tsp = 5ml and 1qt is nearly 1l. When it comes to pasta though it can only be 100g flour to 1 egg.

[Roy Harding]

As a Canadian of a certain age, I was a teenager when the metric system came in. Consequently, I use a mix of units for everyday figuring. When thinking of people's weight, I still think in pounds. When thinking of distance I use kilometres (25 years in the Army cemented that one home), when thinking of liquid measure, I use gallons (imperial gallons, which are bigger than your U.S. gallons).

In the workshop, I work in fractional inches, decimal inches, and metric. My tape measure is both inches and metric. Some of my tool scales are fractional inches, some are metric, and still others are decimal inches. You get used to it. What you want to avoid, if possible, is switching between the systems on the same job. If I start in metric, that's what I use for that entire project, if I start in fractional inches, that's what I use throughout the whole process, etcetera.

Conversion between the systems in the middle of a project is just asking for trouble.

[Kent A Bathurst]

After a career of 30-odd years in octal, decimal and hex I escape to the warm embrace of imperial measurements in the shop to decompress. Fractions must use different pathways in the brain because my shop time is like deep meditation for me ;-)

Base eight...........

You musta had a shop accident - which two fingers did you lose?

No - no - not those two fingers - I can see them from here.

[roger wiegand]

Starting today I would go metric all the way, without thinking twice about it. I'm about 60-70% of the way there now and it is awkward. Being a scientist in the US I pretty much think metric so having to convert to read an inch scale on a machine is a pain. Doing calculations in fractions just seems dumb and an invitation to error. I don't have any tools that read in decimal inches, except perhaps an electronic caliper that will do that trick. One day I will just have a garage sale of all the inch scale tools and be done with it. Half the stuff we get, like "3/4" plywood" is actually 18 or 19 mm anyway and not actually 3/4".

[Jim Becker]

I have the ability in my shop to use both systems having European produced machinery and rules that offer both measurements...and metric is very appealing for many reasons. I have to force myself to do a full project in metric at this point just to get started, but "in the moment" I too often forget to do that! LOL Aside from hole-drilling where I'm very limited with metric, doing the deed shouldn't be too painful. One of these days...

That said and back to the original question. If I were starting out today and knew what I know now, I do believe I'd embrace metric in my shop fully. But as a 57 year old guy who's been using the so-called "Imperial" system for all my life, switching means actually thinking about it...as I already mentioned.

[John Coloccia]

And to John above, how about decimeters? 1 dm is about 4".

Truthfully, I think the decimeter is a far more useful measure for most human sized endeavors. Somewhere along the way, it was declared that thou shalt only use mm, cm, m and km (microns, nano-meters, etc going down). I think decimeters would be excellent in the shop, if only it didn't turn into this useless, oddball unit. I think metric did an awful lot of good for us engineers and scientists. Doing any sort of engineering or scientific work with imperial measurements can sometimes be quite a pain in the butt.

But IMHO, they botched up the actual length of the unit. What they SHOULD have done, IMHO, is made the meter equal to 10 inches, and simply continue from there. This business of trying to define it relative to the size of the Earth was silly, and in the end they didn't even achieve that. Inches, feet, cups, tablespoons, etc are all human sized measurements. They evolved as convenient measurements in day to day life. The meter was defined rather artificially. Maybe they thought it would be used for navigation some day, but pilots and sailors all still use nautical miles, because they're so darn convenient.

Anyhow, as others have said, I just work in both systems, and also interchange fractions and decimals as convenient. It's not so bad, other than having to keep two sets of tools kicking around the shop.

[Keith Weber]

I have decided to get into woodworking and have acquired a number of tools and about to start buying woodpecker measuring devices 1281 square, 32" t-square and perhaps a story stick. The question is should I get imperial or metric?

Just a get a story stick without any units at all, and you won't have to deal with either! Just make everything "about that big", and all the matching parts the same size.

Seriously, though... While metric has its benefits, I find it to be easier just dealing with imperial in the US. Most people here wouldn't know a centimeter from a centipede, and most of the hardware and tooling that you'll find are in imperial measurements. It's easy to get a 1/2" router bit, a 1/8" drill bit, 3/8" bolt, or an imperial tape measure without going further than your local hardware store. But try to find a 10mm router bit, a 7mm drill bit, a 8mm bolt, or a metric tape measure, and finding things you need just got a lot harder -- especially if you need them right now.

In woodworking, I tend to work in fractions as long as it's easy (say, midpoint of 26-1/2" is 13-1/4".) When it does get more difficult, (say 17-5/16" divided by 3), I might just switch to decimals, just to make the math easier. Using decimals in imperial measurements is no different than doing it in metric, so long as you have a method of conveying those measurements to your workpiece. I have both imperial scale and digital readouts on my slider, so I can quite easily work in either. The thing is, though, that the number of times that you need to resort to digital imperial measurements in woodworking is almost never. I also find it humorous when some woodworkers start making measurements to the 1/1000th of an inch (for purposes of accuracy vs. ease of deriving a measurement), and claim that their tablesaw cuts are able to cut to that accuracy.