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[QUOTE=johno]
Not at all of course everbody is welcome but I don't think we should post in french just because some of friends here are from France or Canada.
[/QUOTE]

Thanks for not posting in french, cause' I'm from Canada (born and raised) and don't know a lick of french.

As for the Metric system, I have worked in the engineering field for 8 years and now work in the real estate world and believe me, the only people who use metric in this country (for drawings and such) is the government. Every drawing I ever created in the engineering field was imperial (inches that is), not metric. All home plans are drawn in imperial as well and most of the builders (at least that I have talked with) don't know what the equivalent to 12" would be in metric, come to think of it, I don't know either.

I agree with Kevin's last post, which ever system you choose to use, they will both work just fine.Rod True38696.8626736111

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I use both but find metric easier for me as for 15+ years I imported and distributed European computerized woodworking machinery, specifically 32mm drilling machinery for joining cabinetry using dowel holes that were drilled 32mm on center. When I first started importing and selling this type of machinery into the US market in the 1970's there was no comparable woodworking technology like it in the US.

The advantage when building cabinets with dowel construction as opposed to dados and such is that all of the machining processes can be done on the flat panels at one time without having to move the piece to various machines for various types of machining.

Because all of the machinery I imported and sold were German and Italian, they were all metric so that is how I became comfortable measuring, by millimeters and 1/10ths of millimeters...

I only build classical guitars and the vast majority of them use scale lengths of 650mm with some being 640 to 660mm. Almost all of the patterns, plans and dimensions of the masters of Spanish classical guitars are expressed in metric dimensions. For me it is far easier to work in metric because it works for me...to each his own. I supposed that if I had started with Sloan's book on building classical guitars then I would use a scale length of 25 21/32"...see how silly that sounds.

Many of the materials that I use in classical guitars lend themselves to metric...the veneer I build my rosettes from is 1mm or 1.5mm thick so it is easy to build logs for the patterns in my rosette.

I supposed that if I built Martin derivative guitars that have always been built to inch dimensions that I would gravitate to inches.

Having said that I have no choice but to work with both as most tools and machinery built in the US are inches...I use a Stanley tape measure like many others but use one that is inches and mm's otherwise I have to continuously convert in my head from one to the other. I use a digital caliper that has a botton that convert thousands into mm...all of my rules that I use to build with have both metric and inch measures.

In my shop I have on the wall a cartoon in which I man is at a signmaker and states, "I would like a sign made that says, Think Metric! and I need the sign to be about 2 foot tall by 4 foot wide".

In the past 30 years the only one measurement in the US that has been converted into metric that everyone has accepted without question is the 2 and 1 liter soft drink bottles...

[QUOTE=johno]   

Probably has to do with half of a 1/2" is a 1/4" and half of 1/4" is 1/8" so on ...

[/QUOTE]

Bingo. I believe that's the explanation for the fractional system, John. And all this stuff about inches, feet, yards, etc., is all secondary to the truly important issues. I mean, when it comes to dividing up a pie, which is far more important than any guitar consideration, you first cut in half, right? Then you half that--if you've got three buds over. If your brother is coming over with his voracious kids, then you cut your fourths up again---and stop! I really see no need for anything finer than 1/8th, by the way.

If you're driving, why not just say, "You're now 3/4 the way there".

"Glass is half full."

"This is half-baked."

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As a science student I learned both systems well. As a science and math teacher for 36 years I have taught both systems. The big government push to convert to metric in the 70's was a real flop. They told everyone to convert and then when the auto companies had made about an 80% conversion of their tooling, the government backed off and made it voluntary to convert. I mostly use imperial because that's what I've "used" all my life and everything in this country, almost, is still that way. However, I sure do like metrics. It is very easy to use and if you were just beginning to learn a system, it is sooo much easier to learn than ours. It makes sense, the measurements are self explanatory, where in our system there is very little relevance of a measurement to its name. So much has to be memorized.
Anyway, I have a neat dial caliper (Lee Valley) that measures in 1/64ths and in .001ths. Very nice when your eyes get weak. I can't focus on ruler marks smaller than 32nds.
Are there metric rulers available that are marked smaller than mm? I haven't seen one except in scientific supply house catalogs.
What a lot of rambling. Both systems are fine, the only real problem we have is familiarity.

Sorry to fill up all this space.

Ron

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[QUOTE=old man]
Are there metric rulers available that are marked smaller than mm?[/QUOTE]

I think .5mm is pretty common.

In recent years to earn extra money for my university department, so that we could fund some of our research, my department has acted as an external advisor to a number of the major oil and gas prospecting companies. Part of this has been to use our expertise in seismic work to help on the design and construction of survey vessels and their equiping. Twice we have had to advise the removal of a ship under construction (for US companies)from a American yard to a German yard because of the engineers in the US yard converting industry standard metric measurements in their CAD to Imperial and building with that. Conversions are never precise and even though the ship would have been perfectly well built, the after fitting of the equipment and any subsequent (and frequent upgrading) would have been a nightmare.

The American yards lost about $20m of business on those two ships alone and subsequent orders.

Sometimes little Johnny isn't the only one marching in step.

Colin

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Colin, you made my point better than I could. I was going to say that Americans are losing money over this. The problem was that they tried to teach metric in 9th grade by having everyone learn to convert units. In real life, almost nobody cares how to convert units! A great example is the 2 liter bottle of soda. There actually was a 1/2 gallon bottle of soda at one time, but now we don't even care because we are used to the 2 liter bottle.

And the same thing happens with other measurements. I work in microns at work (1/1000000 of a meter), and I have to go through big convolutions in my head to convert that to inches. That's because it doesn't matter to me what 200 microns is in inches. The grad students have pretty much forced me to think of stress in MPa, which is still driving me nuts, but I'll work my way through it.

Interestingly, bearings and optical scales are two products that are extremely rare in inch units. And the electronics business has gone almost entirely metric since the near demise of through hole components. Bolts and nuts are the last major holdout, but I see english threaded hardware as becoming more and more expensive as time goes on and we lose our manufacturing base. Since that is probably going to happen sometime next week, it might make sense to start changing over.

[QUOTE=Steve Kinnaird] Bingo. I believe that's the explanation for the fractional system, John. And all this stuff about inches, feet, yards, etc., is all secondary to the truly important issues. I mean, when it comes to dividing up a pie, which is far more important than any guitar consideration, you first cut in half, right? Then you half that--if you've got three buds over. If your brother is coming over with his voracious kids, then you cut your fourths up again---and stop! I really see no need for anything finer than 1/8th, by the way.[/QUOTE]
I don't really care what system anyone uses, so long as it works for them, but I find it a major stumper to be given a scale length of 25 21/32", say, and to compute what half of that is. Yes, I know how to do it, and in my head, but it sure slows me down, and I have to double check my work. Half of 650mm on the other hand? 325. Half of that? 162.5. Etc. Pretty effortless to do.

Maybe it is just lack of practice, but I also find it a pain to find, say, the 7/32 graduation on a ruler. Say the ruler is marked in 64ths, then you have to find the 14th tick, and you squint to try to resolve the lines, count over, and try to get it right. I usually get it wrong. However, with a ruler marked with mm, usually every 10mm and 5 mm is marked promenently, so I can find exactly the tick I want without fuss (it's easy to visually choose between 5 ticks). And if the measurement is 0.5mm, then just eyeball halfway between two ticks.

Anyway, that's why I like metric, but I'm sure it all comes down to practice. I'd probably be happy working all in thousandths, too, except that little of the classical stuff is expressed in those units.

Not to mention that 48/64" = 24/32" = 12/16" = 6/8" = 3/4" = .750" = 19.05 millimeter = 1.905 centimeter

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Thank the gas crisis of the 1970. The US was well on its way to converting to the metric system when the gas crisis hit. This was the first time that a gallon of gasoline went to more than $1. Many of the independent gas stations had older pumps that could not be set above $0.99. They had to convert to litres. The chain gas stations had newer pumps that had anticipated this and were capable of prices above $1. As it so happens this was one of the rare times when the independant gas stations were more expensive than the chains since they had to buy their gas on the spot market. The result was that the gas that was priced in litres was more expensive than that priced in gallons.

A few local papers went around to all the gas stations in town and calculated the prices per gallon and discovered that the metric gas was more expensive. Now everybody "knew" that the metric stations over charging and there was a hue and cry. These stations had to upgrade their pumps and switch back to gallons. Metric units in everything became tainted and most consumers prefered English because they felt that they weren't getting ripped off.

The two systems do have a different feel to them. English usually divides into halve, quarters, etc. I find this convenient when reading a ruler. I hate it when trying to pick the correct wrench. I don't like metric rulers. I find it difficult to count all those tick marks that are the same size and I often lose track and have to start over. I love metric wrenches. Quickly, what is the next wrench size up from a number 10? A. 11.

As for temperature, that is an area where I have to convert from C to F. I just can't seem to remember if I need a coat if it is 20 C outside. Fahrenheit is much more tuned to the weather. 0 degress - go outside and you'll die. 100 degrees - go outside and you'll die.

[QUOTE=Colin S] In recent years to earn extra money for my university department, so that we could fund some of our research, my department has acted as an external advisor to a number of the major oil and gas prospecting companies. Part of this has been to use our expertise in seismic work to help on the design and construction of survey vessels and their equiping. Twice we have had to advise the removal of a ship under construction (for US companies)from a American yard to a German yard because of the engineers in the US yard converting industry standard metric measurements in their CAD to Imperial and building with that. Conversions are never precise and even though the ship would have been perfectly well built, the after fitting of the equipment and any subsequent (and frequent upgrading) would have been a nightmare.

The American yards lost about $20m of business on those two ships alone and subsequent orders.

Sometimes little Johnny isn't the only one marching in step.

Colin[/QUOTE]

This I do not understand, because CAD will convert metric to Imperial and vise versa to with in ninth decimal place (.000000000)imperical or metric. So I cant see where the conversion should cause an error in the manufacturing. In perticular since all manufacturing builds to a manucturing tolerance. I am by no means distputing you Colin, but if this is an issue then it is because the engineers gooffed not due to conversion factors. We build shafts for gearboxes that are machined to toerances of .00001" imperical here in the US and we also machine the same shafts and other parts in England to metric of an equal tolerance. All the drawings come out of this office US and there is no issue in conversion factors.

[QUOTE=johno] Colin please take this as the joke it is meant to be

[QUOTE=Colin S] As a European early educated in Inches and now a professional scientist teaching ... Colin [/QUOTE]

See what I mean about pretentious!

[/QUOTE]

We also obviously have very different senses of humour. All scientists, even American ones, only work in the SI units, I see nothing pretentious in that.

Colin

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Michael the conversions on the drawings were fine, The ship yard engineers were the problem, our Naval Architect spent most of his time having wrongly made parts removed and remade, in the exact metric sizes, that had been made to the nearest 1/64" or so, or the nearest Imperial stock item substituted. In the end it was cheaper to have the boats towed back to Germany. With 20 MPa air guns running, danger levels can be high, and risks cannot be taken when attaching European made metric sized kit.

ColinColin S38698.6736111111

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I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

I too use both systems. I grew up using the Imperial system. In college I got quite used to the SI system because of the math/chem/physics classes I took. Then I got a "real" job, working for an independent OilCo, and learned that, not only did they not use SI, but they had a peculiar set of measurements and conventions all their own. Barrels (equivalent to 42 gallons), gauges, pipe schedules, wellhead chokes always expressed in 64ths and never reduced (e.g., a 16/64ths choke was never called a 1/4 inch choke), etc. And one of the oddest of all, a convention of using Roman numerals as short hand suffixes, e.g., 12M did not mean 12 million, it meant 12 thousand. I was pretty confused for a while.

One aspect of the Imperial system that has always been a PITA to me is dealing with the tiny fractional increments, e.g. 21/64". 0.328" is much easier for my brain to process, so I prefer to work in decimal inches, and it is quite easy to convert back and forth between decimal inches and SI units. I have a 12" and a 24" rule that is divided into 32nds and 64ths on one face and 50ths and 100ths on the other. Guess which side I always use?

I also have a couple of scales in cm/mm, and I use them quite frequently, right alongside my calipers and other precision tools that measure in thousandths of an inch.

I build classicals and I use the metric scales for determining nut and saddle lengths and string spacings. Whole numbers -- 54mm nut, 72mm saddle length, 9mm nut spacing and 12mm saddle spacing. But since my metric scales only offer 0.5mm precision, and since a 650mm scale is almost exactly 25.6", I use my decimal inch rule for locating the nut and saddle.

I also have a triple beam scale that measures in grams. I use it for weighing tops and bridges, and I don't even think about converting it to ounces. What's the point?

Best,

Michael

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I seem to recall the conversion to Metric in the US was shot down in the 70's
by the labor unions. They demanded (and they had power then) that the
goverment would have to give every last member a couple hundred $ to buy
new layout tools. May be urban legend, but it's believable.
As for sounding cool, my Hammond Glider sliding table saw, which was
originally used as a printers saw, (I have since converted it to more general
woodworking use) is graduated in Pica. Top that!
Here's a great site for you less cool people:
http://www.onlineconversion.com
-CChas Freeborn38698.4867013889

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The reall reason the conversion was not adopted was the cost of re-tooling was exssesive The unions had complaints, some justified but the cost to maufacturing too re-tool was just too high. Most jigs fixtures and tools used in manufacturing are own and maintained by the maunfacturing company not the workers or the unions. For my company alone the cost to re tool for 1 unit size we build would be in the several hundred thousand dollar range, and that is just one size of one units. We manufacture four major product lines each with muli styles, each with muli unit sizes. So it is easy to see the the cost involved. Just a guess but I would think, it would cost us over several million to convert just one product line.MichaelP38698.574525463

As explained to me by several college prof's and folks in industry, the investment in machinery in this country was too great to scrap it all in favor another system. Think of the Billions of US dollars spent on equipment that was built using the English system. No way were the American industrial giants going to eat all that loss. It didn't make sense. Not just as far as the equipment, but also the retraining of workers. Decimal inches is still a base 10 system like the Metric system, sort of, until you hit a foot.
They were just not going to go the extra mile (or meter) to make a change that was going to hurt their wallets.

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Don interesting observation but I understand that they are migrating to SI units in the U.K. I think it's kinda ironic in that the British invented imperial measure. I was there this past summer -- purchased petrol in pence/litre then had to keep an eye on my mph as I cruised down the other side of the road. I think the U.S. is about the last place on the planet that hasn't converted to metric.

Canada is officially a SI country -- the irony is that building materials are mostly in imperial. I guess I am kinda bilingual as I think in km/hr driving figure out my fuel consumption in mi/gal...think Fahrenheit in the summer and convert to Celcius in the winter .... and work in imperial in the shop Anthony Z38698.635462963

If you've ever purchased steel products, that is all screwed up too. Most of it is made in Asia or Russia for the east coaster and it is all imperial.
Anthony, is right that we are an SI country, but I also have found that the majority of the manufacturing industry I have delt with all use imperial measurements as their standard.

Here is a file 2005-12-12_184238_HSS53to12.pdf to a steel company based in BC, notice all the measurements are imperial, including the stock lengths, if you want metric, it's like this 101x101x6 is a 4x4x1/4 HSS (that's hollow structural section, not high speed steel ), seems that there is no rime or reason. I actually place my bridges using metric as I don't have a long enough ruler with small enough fractions for locating the bridge.Rod True38698.7864236111

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The only manufacturing I know that commonly uses feet and inches i.e. 10'-9 3/4" are architectural, civil engineering and building trades (homes, office buildings, land plats and such)
Here in the US Machine or mechanical manufacturing use inches in common fractions for dimensions that require a tolerance of +/-1/16” or more (129 ?”), 2 decimal for tolerance of +/- .045 (129.75) and 3 decimal for tolerance of +/- .010 (129.750) and 4 decimal for +/-.0045 (129.7500) and many more ways to describe decimal tolerances greater and lesser such as 129.750/129.751 for a limit range. These tolerances vary slightly from shop to shop but are commonly clearly defined on the face of the drawings. I could go on and on but my point is that if proper engineering is applied to a set of drawings imperial or metric can be applied and converted as accurately as required for the process at hand. Any errors in conversion are due to lack of applied engineering not to the unit base used.

I was inch-centric until I started working in circuit board manufacturing R & D.I use both now, but mostly inches because that's what's around. It was painful at first, always having to convert mm to inches so that I could get an idea of the physical size of an object, but after awhile, I found that I no longer needed to think in inches: "let's see and eighth of an inch is a little over 3 mm, so 6 mm is a bit under 1/4". All of a sudden, I just "knew it." I have, however, discovered that I think differently in fractions than decimal. In fractions, I tend to think around a larger fraction, then sort of count smaller fractions from there. Like, to measure 15/32", I'll find 1/2", then count back 1/32" to get to 15/32". Pretty inefficient, but that's just me. With decimals, metric or inch, I just go right up the scale, straight to that point. Metric in general does seem more logical, especially since I got fluent with it, but it's a pain when you're the only one around that's using it. Sort of like learning a new language. You work at say, Ukrainian, and get fluent so that you can think in Ukrainian and don't need to translate anymore, but if you're surrounded by English speakers, what're ya gonna do?

Pat

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I mix it up as I am working. I do have one of those nifty tables from the Stew-Mac catalog pinned up next to my bench to help make a quick conversion.

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Heh. I've got basic fractional inch -> metric conversions stamped on the back of my 1m metric+imperial rule.

I think if you memorize basic units of metric to imperial, conversion becomes a lot easier. For example, 100mm is about 4". Therefore, 25mm is about an inch and 300mm is about a foot. This helps with quick reference.

I used a metric ID/OD grinder for a while and that was a real treat... until you converted! What a pain!

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I orriginally started learning Standard in school and then learned metric and totally ignored english system. In canmada we do you both all the time and in building I go back and forth. Of course don't forget, a yard in Canada is different than a yard in the US which is different than a yard in the UK. Not much but slightly different in length so when real accuracy is needed it can be a problem. Likewise a Canadian Gallon is not the same size as an american Gallon. As well, in the building industry we still talk about everything in feet and inches but some of our 4'X 8' sheets are not actually 4'x8' they are a metric measurement that is really close. In the end for what we do I figure it doesn't mattet which we use.