going metric

[pingvinlakrits]

Sorry Nick, I don't really buy into that guy or the arguments. From the link provided:

"Did you ever watch a seamstress measure cloth from her nose to her fingertips? That human dimension is normally about 36" or a "yard of cloth". It would take a basketball player with arms over 3" longer to measure meters that way."  ??? He uses very vague descriptions to prove a point of Imperial being superior to metric just shows he does not grasp the concept of metric. There are umpteen for the americans unknown similar vague measurements that have been with us from medieval times... ...long before the settlers arrived to America. Here in Sweden we have quite a few that most Swedish people haven't heard of in this generation, I happen to know some of them as I like history.

And saying metric doesn't break down nicely - well I don't know. The tooling industry and carpenters in the rest of the world seem to get by just fine. It's just the same the other way around; if I use the well known dimensions that are used on a daily basis in the metric system the breakdown/conversion doesn't work out so nicely for inches either, but I wouldn't say that inches are useless because I cannot straight convert 5mm (1/2cm) to a nice, even figure in inches. It is not the conversion between two systems that are important, it is the merit of the system itself.

Just as well as you can say half an inch you can say half a cm, half a mm etc... Half a mm (which is the tolerance I normally aim for in general woodworking) is more than adequate for most common woodworking applications.

On his own products he writes;
"The handwheel on the inch models moves the slide .050" per revolution and has 50 graduations of .001". The metric model moves the slide 1mm (.03937") per revolution and the handwheel is graduated into 100 divisions. Even though the metric handwheels have finer graduations, this doesn't necessarily make them more accurate, as you don't have to stop exactly on an engraved line. You can interpolate between lines."

So, is it more accurate, or is it not? Contradictive, at least. It is like he doesn't want to admit to that the graduations ARE finer.

But hey, by no means am I to judge or convert anyone from a system they feel comfortable with, just don't tell me metric doesn't do this and that that Imperial does, there are workarounds, benefits and pitfalls with both systems. And I surely don't mean to step on anybodys toes, or pride. It's just that pride aside I think Imperial is obsolete and by not letting the next generation of americans grow up with metric (or both) will hamper them if they want to go abroad and make a living doing carpentry or other handicrafts as the rest of the world is getting by with metric.
Be stubborn all you likes, I still like you guys, just don't ask the world to embrace a system you are fond of/stuck with and do the youngsters a favor and let them learn both and decide for themselves. 

 

[pingvinlakrits]

I still say my projects look the same whether I use metric or imperial so who the heck cares.

That is a good point Nick, and I totally agree!
If you are metric savvy you will expand your customer base exponentially though.

 

[Peterm]

From the link provided:
"Did you ever watch a seamstress measure cloth from her nose to her fingertips? That human dimension is normally about 36" or a "yard of cloth". It would take a basketball player with arms over 3" longer to measure meters that way."

Had to laugh at that one. Just for fun, I measured my nose to the tip of my fingers - at a whisker over 1 metre (40" and a bit if you must). I'm 5'11" (1803mm...); my tailor loves me, and even my mother's run out of 'knuckle-dragging ape' jokes :

Seriously, use whatever suits your fancy, or whatever suits the project; it really isn' that big a deal.

Cheers, Pete

 

[glass1]

Great debate. It's amazing how passionate people get about such things. Imagine if we cared as much about peace, equality, the environment, and universal health care . Bengt 

 

[tallgrass]

the whole metric thing is interesting. Obsolete??? here is a simple example. take your meter and divided it into three equal parts. you will be left with an object that can not be described precisely using the metric system. if you take the same object and divide it by three you will ,because of the a non terminating decimal ,get three objects that are not 1/3 of the whole due to the required rounding error, so if you were to join the three back together you would not have your 1 meter.  No this is not a huge problem for most people. This is just one example that i think is a problem with a fixed 10 base system, it is not just the factoring of three. The problem of rounding error and the propagation of significant rounding errors is a problem.If it were not for digital measuring tools the metric system would be too unwieldy. even with these tools there is the problem of accuracy due to the analog to digital  conversion that takes place and the rounding error that comes with it. An advantage that i see with the imperial system is you can choose your unit size or resolution to match the scale that is needed.I am not saying that the imperial system is perfect but withing the imperial is a ten base system and a fractional system, if you choose ,while the metric system only has the ten base system. as i have said in the past i use both , i find it funny that a lack of choice is defined as progress. i also think that the adoption of the metric system by countries was more due to geopolitics than the (theoretical ) superiority of the metric system. this is definitly a coffee shop discussion, right after the conversation where all of the worlds problems are solved. it is fun though. ;D

 

[VictorL]

the whole metric thing is interesting. Obsolete??? here is a simple example. take your meter and divided it into three equal parts. you will be left with an object that can not be described precisely using the metric system. if you take the same object and divide it by three you will ,because of the a non terminating decimal ,get three objects that are not 1/3 of the whole due to the required rounding error, so if you were to join the three back together you would not have your 1 meter.  No this is not a huge problem for most people. This is just one example that i think is a problem with a fixed 10 base system, it is not just the factoring of three. The problem of rounding error and the propagation of significant rounding errors is a problem.If it were not for digital measuring tools the metric system would be too unwieldy. even with these tools there is the problem of accuracy due to the analog to digital  conversion that takes place and the rounding error that comes with it. An advantage that i see with the imperial system is you can choose your unit size or resolution to match the scale that is needed.I am not saying that the imperial system is perfect but withing the imperial is a ten base system and a fractional system, if you choose ,while the metric system only has the ten base system. as i have said in the past i use both , i find it funny that a lack of choice is defined as progress. i also think that the adoption of the metric system by countries was more due to geopolitics than the (theoretical ) superiority of the metric system. this is definitly a coffee shop discussion, right after the conversation where all of the worlds problems are solved. it is fun though. ;D

Hmm....
I took one Inch and tried to divide by 3.... 

 

[tallgrass]

so how did you like your 1/3 of an inch units......groovy ;D

 

[Wim]

@ Tallgrass, dividing a meter by 3 and trying to end up with a meter by adding those 3 pieces is a matter of tolerances. Making parts with dimensions within certain tolerances was one of the pillars of the Industrial Revolution.
There is no such thing as an absolute meter, it is always within tolerances. So if you are working your wood with a tolerance of 0.5 mm, you will end up with a meter with a tolerance of 1.5 mm. The same applies for inches and feet. 

 

[pingvinlakrits]

Tallgrass: I think (I hope) you understand that my postings are partly tongue in cheek. Since I am at home and down with the flu, of some sorts, maybe I come out as being blunt - that is not my meaning. I do agree that it is a nice coffee shop discussion. And I am sitting down with a Latte at home, though I should be drinking tea.

As for the dividing things down there are many examples of where inches and centimeters don't break down into nice even figures - but that has never stopped anyone dead in their tracks has it?

On Whims posting I would like to add that it would be +- 1.5mm in total so it could be dead on or dead wrong. But I will boil that down to user error more than insufficient metrics. Last time I had to divide a metre length of wood into three parts it didn't pose a problem, the tolerances were within the spatial movement of wood.

...on more than one occasion I have made a few pieces 10cm (100mm) short, owing to user error (being tired, and) reading off the red side of the Talmeter scale when I haven't directly transferred the readout but folded the talmeter down and then used the black scale for marking the piece... That isn't as amusing as making it 10cm too long, which usually never happens...

...would I be safe to say that had I worked in inches I would be just as error prone? 

 

[pingvinlakrits]

I will make a sincere effort to try and learn Imperial, just for the heck of it. At least then I could follow your discussions on jigs and projects and maybe even visualize the scale of things you are talking about. Just don't expect me to learn overnight.

 

[tallgrass]

@ Tallgrass, dividing a meter by 3 and trying to end up with a meter by adding those 3 pieces is a matter of tolerances. Making parts with dimensions within certain tolerances was one of the pillars of the Industrial Revolution.
There is no such thing as an absolute meter, it is always within tolerances. So if you are working your wood with a tolerance of 0.5 mm, you will end up with a meter with a tolerance of 1.5 mm. The same applies for inches and feet.  Cheesy

As a ME i understand the concept of tolerances. i am not referring to the limitations of an individual's ability to measure, i am referring to actual mathematical limitations to start with.If you can not even get there in theory good luck getting there in the real world. Look ,i get the ease of use of the metric system. as for the definition of a meter it is an absolute or it would be of no use in calculations. It is the world of calculations it is a real problem. i think the idea of significant rounding area is being lost here. here is a simple example you want to find the middle of 3/4 of an inch. simply turn it into 6/8 divide by 2 and you have 3/8 , no problem. i think you would find the induced error in marking 3/8 would be less trying to mark 9.525mm.
as for tongue and cheek i get it. i find this whole thing like chewing gum, got to have a little fun now and again. ;D ;D ;D. that is why i said this belongs in a coffee shop.
On a serious note, do you find the mm to be an adequate minimum unit? .5 is not useful on a work shop rule. i find the mm too course. and 0.xx mm very unwieldy.I have tapes and rules that go to 64ths 128ths 100ths...this is not a slap in the on going school yard spitball contest but i a really curious. you can not all be telling me you just guesstimate in between the mm marks?

 

[Wim]

As a fellow ME, during my education I was used to work with tolerances of 0.001 mm in the machineshop. I ended my career at a shipyard, where a gap of 10 mm between hullplates was no problem and only meant more welding-material. Thanks to Festool I'm able to do woodworking with tolerances of 0.1 to 0.2 mm, even if I don't have to be that precise. It is just a principle  ;D

 

[pingvinlakrits]

Tallgrass: Well, it goes the other way around, say if I take something that is a solid 4 centimeters = 1.574... (...803 149 6) inches and want two halves of that which is a solid 2cm  but a seemingly messy 0.787... (...401 574 8 ) inches would you say Imperial hits it right on the money or don't you find it kind of awkward?  :

For field work, yes, I guesstimate that half a mm - if needs be; it is just 0.019 inches and how often do you NEED that precision on site? If it fits it fits, if you measure an interior trim and add that half a mm you can always make it fit. Getting half a mm off dead on is something pretty much no one sees, if the piece itself is 80" long most people think you mad for wanting to fit it with 0.019" precision. I have a smaller 300mm ruler with me which is fitted with half a mm markings, it gets out for some stuff but mostly it stays in the bag.

For shop work I do have half mm scales though they seldom get used, that half a mm doesn't occur that often in real life and if you measure things in solid mm's and cut them to size with the Festools they usually hold that tolerance dead on. If someone wants a custom built hardwood shelf they usually order it to spec to the centimeter and onnly occasionally to the mm. No one has ever asked for that "...and a half mm..."  ...yet. With cruder tools than the Festool gear I custom built old style big window frames and windows and considering that there was a hole in the wall to work with you had more than a mm play in whichever case there was no point in going for even that mm precision as the hole itself would deviate some +- 5mm from end to end (and you don't fit window frames that way anyway). Still both frames that were supposed to be 1925mm wide x 1240mm and 1930mm x 1440mm respectively weighed in on the mm and slid into their slots like the proverbial glove. All twelve window followed suit with equal precision which was a relief as the owner was anxious to have them fitted and was sitting with his Coffee watching us fitting it.  8)

I agree that a mm can be a wee bit course for some stuff (inlay work perhaps, such as Nickaos excellent work) though the workarounds are never that hard. For routers and many other tools there are settings down to 1/10th of a millimeter (some 0.003 inches) and I have yet to find a project where I have needed that fine graduations. Which is a good thing because I would need a magnifier to even make that out...  ...as with Wim I find that the .1 to .2mm tolerance is more than I need, but I find with that leverage hitting half a mm is easy. ;D

Out of curiosity; what is the accepted minimum tolerance for the kind of work you do?

So wish I could offer you a Coffee and spin a yarn or two. A metric yarn. You could spin the Imperial yarn  ;D

 

[pingvinlakrits]

I had to rewrite my post a few times as the fever is getting the better of me, must pass out - sorry sign out and stuff my face with something nutritious.
Keep it coming though.

1/1000th of a mm is 0.000 039" and in any case I hope no one asks that precision of me. Well, maybe if my fianc?e asks me why I sit around the computer instead of doing something useful I might have to resort to answering with much greater precision but my grasp of inter-gender-lingo doesn't allow for such fine nuances. We have a saying you have to "weigh your words on a gold(en) scale" when talking to a woman but I don't know what measure that is in. Probably no standard known to Man.  :

 

[tallgrass]

.001mm that is great. tough stuff.....how did you hold that?+-.0005mm? what was the processes? so how do you measure in the shop tenths of a mm? i have not seen shop measuring stuff that broke down mm into tenths......i hate guessing where i am? i do use calipers and micrometers ect, but that does not get me more than 1 foot. ;D ;D ;D ;D

 

[pingvinlakrits]

Tallgrass; I for one wouldn't claim I can produce work with precision down to a tenth of a mm, though I could dial that in on the router. If routing a circle for a recessed speaker element I can get close but reproducing it for the next speaker box would probably not get that 1/10th of a mm, my dexterity would probably set things within 0.2

 

[tallgrass]

i think i have made a mistake here. i do not mean moving back and forth between systems....that would be suicide and i would shoot myself if i had to do that. i am talking about staying in a measuring system and dealing with the mental gymnastics that come with each one. depending on the project i pick one and stick with it.

as for the tolerances  i deal with, they range  from temperature compensated fitted components to +-.001 of inch. though +-.005inch (in imperial for you) is good in standard terms. it depends on what it needs to be. also you have to take into account the statistical wear compensation QAQC the CNC machines use. As the machinists tell me "the real world can not be found in my blueprints". when they tell me that, i usually have to redesign,(meaning the problem is on my side not theirs. ;D ;D ;D there is usually a difference between what people say their tolerances are and what they REALLY ARE GETTING. It can be humbling to see what comes back from the metrology lab especially if my hands are turning the wheels. the machinist love when i make them look good. ;D

when it comes to my wood working i have found the metric system mm too course so i usually go to 64ths. though for a great deal of stuff i find the mm just fine if i get to keep it to the whole mm. that means i am doing the designing and have control.

 

[tallgrass]

I wouldn't be able to read any scale which was in 1/10th mm increments and any pencil I could find marking that would probably snap when I tried to.  Grin

i agree with you on that.

that is a problem for me with the mm system. for wood working a mm is too course and a tenth of a mm is too fine.  i use Japanese marking knives in my endless pursuit for precision. though i am sure i am not as accurate as i think i am being but in my shop at home i am awesome and do not make mistakes. ;D ;D ;D ;D ;D i am soo good i have to wear sunglasses when i look in the mirror so i not damage my eyes. by the way i have mirrors in my shop so i can observe my awesomeness. ;D ;D ;D ;D

 

[Wim]

I hope it is not getting too much off-topic.
I started my education as instrument maker. We had part of the machineshop and the testroom at a regulated 20?C to eliminate the effects of temperature changes. We used gloves to avoid fingerprints. Measuring was done with a big collection of micrometers, we even had one with a max. length of 1 meter. I guess our results could be used in satellites of NASA.
But I had no patience for instrument making, so I switched to aircraft engineering. I found that too restricted in Europe so I ended up in a more general Mechanical Engineering.
Most of my career I spended with electrical/hydraulical engineering and later in ICT. But I enjoyed it all.
Now I'm retired and are carving wood  ;D

 

[tallgrass]

a yes temperature control ,  ;D here is a question,,,,,what system was used for the Apollo project,,,,,????