Metric Stacked Dado?

[bluzcat]

Is there such a thing? It seems like most plywood thicknesses sre actually closer to a nice round whole metric number and having a metric stacked dado set might be real handy. Just a thought.

[BigguyZ]

Well, using shims you can always get to a metric number...

[Black wallnut]

I do not get the whole metric thing. Are folks just afraid of fractions? Both imperial and metric use decimals.

[RodKirby]

I do not get the whole metric thing. Are folks just afraid of fractions? Both imperial and metric use decimals.

Oh, dear - Metric rules OK?

A millimeter (mm) is 1/1000 of a meter - NO DECIMALS

ALL plans (by law) specify mms, so there are no mistakes.

Bet I can measure off 2069mms, faster than you can do 81.4566"

When we switched to metric, it took me two days to think - Why didn't we always do it this way?

Having said that, I still can't "picture" a person's height in anything but feet and inches

[LCHIEN]

i'm told that EU rules prohibit dados on table saws as being too dangerous, With the largest market for metric dados thus off the market, there won't be too many around, if any. EU table saws are required to have short arbors to enforce this law. Plus the EU saws have different standard arbor diameters further complicating the issue. I don't think there is a market for metric sized dados altho there's no technical reason one could not be made.

In reality theres very little difference between 3mm (.118") and 1/8" (.125").
it's easy to memorize the following conversion: 6mm ~= 1/4" as a baseline then it follows
1.5mm = 1/16"
3mm = 1/8"
6mm = 1/4"
9mm = 3/8"
12mm = 1/2"

Just use shims to make the dado any width you wish. I think anyway there are mm sized plywood (from Europe, like baltic or Finnish birch ply) and inch-sized plywood which are all shy by a few 1/64ths and to no real standard of thickness.

[Black wallnut]

Oh, dear - Metric rules OK?

A millimeter (mm) is 1/1000 of a meter - NO DECIMALS

ALL plans (by law) specify mms, so there are no mistakes.

Bet I can measure off 2069mms, faster than you can do 81.4566"

When we switched to metric, it took me two days to think - Why didn't we always do it this way?

Having said that, I still can't "picture" a person's height in anything but feet and inches

Yup no decimals like 7.62 x 54R or 7.62 x39 or 5.56 NATO! Ammunition has decimals. Lets now look at thread pitch m6 x 1, m4 x .7, m5 x .8; okay so thread pitch is not exactly linear measure however it is decimal. So how about food, Italian pie to be exact: three close friends go out to eat together and equally split a pizza each gets 1/3 or .33. Which is the metric quantity? Same three guys, same pizza, this time guy one eats 1/3, guy 2 gives half of his third to guy 3 who eats it, so one guy eats a third, one a sixth, and one half. Is there a metric equivalent other than a fraction or decimal? Did not think so. My house is 3.2 miles from my work and the metric equal is expressed as so many K and so many M or x.zK? How is either easier? Okay how about landmass or acres, section, etc? 640 acres = one section = one square mile; must we rewrite all maps so that they read hectares? Resurvey the entire country to find corners? Not to mention rewrite every single legal parcel description, and at what cost? The point is Rod et. al. so what if the metric system works for others. I'm happy for ya'll. The only and I do mean ONLY good thing about the metric system is that it is based on ten. If schools would return to actually teaching math multiples of 12, or fractions based on one half as well as decimals would not be such a problem to learn. I prefer to buy my adult beverage by the fifth rather than 750ml.

A thousandth of an inch is finer than a mm; when precision measurements are expressed as a number plus decimal as is so often the case metric loses it's appeal to me any way. I think I learned or was supposed to learn in 7th grade how to convert a fraction to a decimal so what is the point if it is not to teach less math or worse reduce the need for math.

[leehljp]

Is there such a thing? It seems like most plywood thicknesses sre actually closer to a nice round whole metric number and having a metric stacked dado set might be real handy. Just a thought.

Others have already said it (use shims) but they don't go into detail as to the other problem you would have. IF Metric, so would the arbor / shaft hole be, and consequently it would not fit your US made saw arbor.

I brought two of my Japanese circular saws with me from Japan along with several blades. The hole in the blades are metric in size. The arbor is also metric. It has been a few years since I measured and tried but the US blades and Japanese blades were not compatible on the same circular saw. I have a US Makita and 1 Japanese Hitachi circular saw and one other Japanese circular saw.

I have forgotten which blade has the largest hole, but the one with the largest hole will fit the other with the proper adapter, but not vice-versa - of course. The adapters that are available in some hardware stores and home centers in Japan still did not make the blades match up to the imperial side. I don't know if the problem that I had was a "Japanese" thing or if it was consistent with metric/imperial differences all the way around the world. i.e. - it seemed to me that the adapters were not intended to make metric work on imperial or imperial work on metric, but rather make metric adaptable to a different size.

By the way, I did look up online and there are a few places that make metric blades for sale in the US. Expensive but they are here.

[leehljp]

Ot

Mark,

Your explanations brought back the memory of a discussion I had a few weeks ago with a psychology professor in Memphis who also writes entrance exams for some prestigious universities.

Our discussion focused on cultures and learning/response traits by culture. He brought up the fact that the US is not as far behind the world in math as is currently perceived, tested and reported in the current general world wide educational testing system. Current testing world wide is based on memorized formulas and equations rather than deductive reasoning skills such as you put forth.

The kind of test used - will determine the rated outcome of a particular group. Basically in the US (and the overall western mindset of the English system) do better with the "reasoning" skill tests than the memory / formula tests. The move to the metric system was also a move into the "memory" system in educational institutions.

In a sense, Rod & Lorings metric discussion versus your (and others) Imperial system is somewhat like apples and oranges. Metric discussion are usually inductive in nature - move from specific to general; Imperial discussions usually are the opposite - deductive or from the general to the specific/conclusion.

Rod and Loring grew up with the Imperial and switched/moved/studied under the metric. They got the best of both worlds - reasoning skills plus memory based.

Metrics are more simple overall to learn and apply and do not get deep into the reasoning skills, requiring less brain power to use. That is also its downfall. Because one can get to the end result fast on a "10" based system, "thinking and deductive reasoning skills" are decreased. But for those who were raised on one (Imperial) and move to the other (metric), they often don't realize how much their "Imperial" background has helped their reasoning, logic, deductive, problem solving reasoning skills.

Easy memory based systems used early on in a person's life often reduce deductive reasoning skills. I know that from living in a society for 25 years that centered squarely on "memory" based learning.

Not totally unrelated: There are as many geniuses per capita in illiterate countries as in literate countries. The difference is that they just can't read, as is judged from a western mindset. Their deductive reasoning skills in survival are generally far beyond those of the literate countries.

[gerti]

Put these drill bit in order from smallest to largest: 1/4", 37/64", 9/16", 5/8"

Put these drill buts in order from smallest to largest: 6mm, 4mm, 7mm, 3mm

Now laying next to each other, how wide would that be?

Still want to argue against metric, Mark?

[Black wallnut]

Put these drill bit in order from smallest to largest: 1/4", 37/64", 9/16", 5/8"

Put these drill buts in order from smallest to largest: 6mm, 4mm, 7mm, 3mm

Now laying next to each other, how wide would that be?

Still want to argue against metric, Mark?

Sure I do! Include number and letter drill bits as well. I am not afraid of math. Your exercise is fine on paper, as an actual hands on exercise it would be simple. Correct me if I'm wrong but did not President Nixon decree that we would switch, and yet decades later we are not much closer. I'm good with that. Not sure which came first math understanding or deductive reasoning skills but I have both. Easy does not equal best. If your only criteria is ease of understanding and no need to think then easy wins. There are students that do not understand metric and yet do understand fractions. Is metric better for them? My main point remains that for precision measure decimals are required so the base of the measure is not as important as the relative size of the smallest unit. For example a bar of metal may be temperature dependent in size of 1.4995" to 1.5" ; express that in metric and how many decimal places do you need?