Inchies

Not always skate - it's the number of pixel per inch that decide that, printers go way higher, the majority of cheap inkjet can hit 600DPi... Then it's 600px by 600px

Of course that image would print as a 1X1 because it's 72 dpi and printed at that resolution, monitors can do it too...

It's a weird one but often the explanation for why images change size between printing and screens, paint being the worst offender...

bad explanation and unnecessary pedantism but meh, it's worth knowing this stuff sometimes...

Hm... Didn't know that. I just got learned.

Mod up.

There's a little more background to the 72x72 metric (it's not really based on screen pixels, which vary by monitor): traditional graphic designers used picas and points, rather than fractions.

6 picas to an inch, 12 points to a pica...which works out to 72 points per inch.

So it's not even a Photoshop (or Illustrator , Indesign, Quark, etc.) thing, really.

I was more trying to illustrate how an images properties change it end size, I understand the concept of points and picas but know I know why they're there, cheers moon...

Sorry, KJL, I was trying to "mod up" your comment as a good and useful one. (the picas and points info was for Skate####.)

No worries, it does at least give a reason for the standard sizes, rather than it "just being so"

While still in college I did "pasteup" for the local daily newspaper. I bet I could still "back in" a galley of type today, if I wanted to.

No need, of course, with desktop publishing and pagination. Another lost "art" ;-).

More typesetting trivia for those not completely bored--the standard unit in the postscript PDL (defacto standard for typesetting languages) is also 1/72 of an inch... Postscript predates Photoshop by a few years.

SWEEET

The more the merrier :-)

i don't have a cat

Oh sure you do. He just hides most of the time, but goes on instructables whenever you're not looking.

The comment was from the omniscient narrator of this story, who doesn't need to see what's going on...

π is exactly three

"I'm sorry it had to come to that."

whoa, now I got nothing to memorize!

Yes you do .. 4 is now 3.6.

!!!

25.4mm

L

If your going to be picky, at least do it properly.

Its actually 25.40mm.

Sorry, forgot that. The zero could have serious implications for high precision engineering projects. L

Um, that extra zero doesn't do anything to convey any more information then lemonie's use of the figure with out it. :-) I mean, 4/10ths = 40/100ths

Precisely so, unless you are comparing multiple numbers with at least one of them having a value greater than zero in the hundredths place, it's standard practice to leave out the extraneous zeros.

Yes, the only time that I know of that they become useful is when lining up a long column of numbers, some of which go out to that point, in a subtraction or addition problem.

Extra zeros indicate additional precision/accuracy. 25.4mm means the actual value rounds to 25.4 (+/- 0.05mm, more or less); 25.40mm means the actual value rounds to 25.40 (+/- 0.005mm) Of course, many people aren't careful about using this convention, and 25.4 may mean exactly the same thing as 25.40, but not always.

Thank you westfw, saved me alot of time explaining that one..

*cough* and he spelled everything correctly *cough*

I seriously hope your not mocking a persons disability there kelsey...

Not at all.

Sure seemed that way.

Oh, stop it. You know full well he wasn't. And you haven't made a disability common knowledge.

My apologies then.

Its cool, I just like to make a stand for those of us whom beyond a spell checker, can struggle with such things.

. Then make a stand and quit beating around the bush! I'm assuming you are talking about dyslexia, but you don't say. Looks to me like you're just trying to put Kelsey in an uncomfortable spot for giving you some good-natured ribbing.

Actually, there are many reasons, for example the recent guy whom was down by one hand, and was therefore slated as a younger person, stuck at home, amongst other things.

No, that user was looked down on because of his attitude towards the staff and contest, not for any disability.

You know, I was feeling guilty enough for sidetracking this topic (which is about a class of ART projects. Remember the "inchies" ?) into a technical discussion about measurements...

xD I just had that same thought. But I couldn't let that pass...

(removed by author or community request)

Regardless of my problems, and wether they are diagnosed, i would prefer you not to discuss them openly.

. I was a bit shocked that she made that statement ... until I found where you all but announced it here.

I would never have said it had he not said it himself.

All right, I removed the comment, but if that's the case it isn't at all fair to jump down Kelsey's throat involving something you don't want discussed openly. Either it's common knowledge or it isn't - and if it isn't it's not right to attribute malicious intent to him.

Jeese you people need to cut out deh squabling.... >drags apart gmj and lira Now, make nice, make up and behave!!

It's not about me and him, it's about him and kelsey - we all know he'd rather swallow glass than mock someone with a disability, and it's silly to accuse him of it.

Agreed.

But you've openly stated multiple times that you don't care about spelling and grammar, which could easily lead to the impression that any mistakes are because you simply don't expend the effort. (I'm not saying that's the case, just that people might easily think that because of things you've said in the past.) So all things considered it's a little strange to "take a stand" against a small joke.

Im always taking a stand, do you not remember the discussions on the grammer nazi group page?

De donde? I might just be unable to find it, but there are two Grammar Police groups, but only one thread in one of them, and there's no conversation between us there...

Must have been elsewhere, also, note, i never stated you were involved.

I concede it may be of use when dealing with figures and computers, but contend that the reality of the figures still remains the same, inferred meanings aside. ;-)

. It's not just "figures and computers" it's any scientific/technical endeavor. . Yes, in this case, they are exactly the same to most DIYers, but try having a machinist build you a 3.0" part when you actually need a 3.000" part.

Then, you are saying that the machinist can not be accurate if he see 3 " but if he sees 3.000 " he is more accurate? I am glad I do not work with machinists LOL To me, a 3 " part is not rounded down from 3.1 " nor from 3.00000001 but it is 3 " *shrug*

sounds like the type of person you could confuse by asking for a bolt the length of the square root of one ;-)

I'd expect a reasonable machinist to send back the plans if they said "3 inches" requesting clarification...

It's more common to see issues when there are more decimal places, of course. Consider the difference between a hole through which you have to fit a 13mm bolt, vs a hole expected to mate to a 15.00mm PISTON. Not only does the latter have to be more accurate in diameter, it has to be more accurate in "roundness", and it probably needs a whole different machining process to get it (costing more, so you don't just tack extra zeros onto ALL of your measurements.) Presumably there is a whole ciriculum on how to fully specify a part "to be machined" that the Mech Es learn. Hopefully. Apparently there is a bit of rivalry; there are songs about it...

The Designer

The designer sat at his drafting board
A wealth of facts in his head was stored
Of what can be done with a radial drill
A turret lathe or a vertical mill
But above all things a knack he had
Of driving machinists completely mad

So he mused as he thoughtfully scratched his bean
Just how can I make this thing hard to machine
If I make this body perfectly straight
The job would surely come out first rate
But that would be easy to cut and pour
It never would make the machinist sore

So Ill throw in a compound angle there
And a couple of tapers to make them swear
Now brass would do for this little gear
But thats too easy to carve I fear
So just to make a machinist squeal
Ill have him machine it from tungsten steel

And Ill put the holes that hold the cap
Down underneath where they cant be tapped
Now if they can make it theyll do it by luck
Cause it cant be held with a dog or a chuck
And it cant be drilled nor planed nor ground
So I think my design is completely sound

The designer sat back. His plan he surveyed
The screwiest thing he had ever made
He signed his name with a line so thin
Then put down his pencil and started to grin
He shouted with glee, Success at last
Ive designed a part that cant even be cast.

Author unknown. plus Jordin Kare.

The Engineer

Some plans came down to the engineer
With lines so fine and dimensions clear
Showing gears and levers and angles and bends
And inside out widgets with chrome plated ends
For a gadget to leave any craftsmen dismayed
And it's heart was a part that just couldn't be made

For the engineer sighed as he studied those plans
And he read the demented designers demands
Then he called in his techs and he said to his crew
This guy seems to think that there's jobs we can't do
And parts we can't build so let's give him a thrill
We'll build his machine and then send him the bill

Now his tungsten we'll carve with a laser or two
We can hold it with magnets or vacuum or glue
His tapers we'll trim by computer control
Triangular bits will drill all his square holes
We'll put it together and try to stay calm
‘Till we weld it all up with a small fission bomb

Now this micro-inch finish won't cost him too much
So we'll plate it with platinum, seems a nice touch
But the tricky bits here are these spheres within spheres
The (cline)-bottle tanks, the irrational gears
The left-handed (blivets) I'll buy off the shelf
But I'd better sneak in and make this part myself

The designer came down and his jaw it did drop
At the thing sitting there on the floor of the shop
The engineer grinned and he pointed with pride
At the parts that were whirling and glowing inside
For there's no job too tough and there's no job to queer
For a MIT grad hyperspace engineer

By Jordin Kare, I think.

It falls into a matter of perception then? I see 3 " as (once again) meaning precisely 3 inches, and not a micron over (if I can get such precision).

Now, if we have 3.1 as opposed to 3.01 or .00000001 then we have a difference, but to assume a rounding gives me a queasy feeling inside ;-)

It's a matter of perception that it ISN'T important, I think. When you say "3 inches" what you really mean is "close enough to 3 inches that I can't tell the difference." But how hard are you trying? You wouldn't expect 3.4 inches. But down around 3.1 inches you'd surely need to pull out a ruler, and at 3.05 inches probably your ruler wouldn't be much help and you'd need better tools. And .05 inches is still pretty huge if you were hoping for gas-tight or water-tight.

Perhaps the LACK of extra zeros doesn't mean anything important in average life. But the PRESENCE of extra zeros has an exact meaning that is important in some contexts.

(Of course, the inch is defined to be exactly 25.4mm, so you can add some extra zeros on there if you want!)

But the PRESENCE of extra zeros has an exact meaning that is important in some contexts.

With this, I am not in disagreement with. Actually I am not disagreeing at all, but just noting that from my perspective, 3 inches means precisely that (as precisely as I can get it anyways). It is the context and the perspective that makes it meaningful or not.

You wrote, "Presumably there is a whole ciriculum on how to fully specify a part "to be machined" that the Mech Es learn."

Take a look at http://www.efunda.com/designstandards/gdt/introduction.cfm, in particular, follow the links on 2D and 3D datums in the left sidebar.

:D

> he sees 3.000 " he is more accurate?
. Exactly! It's not that the machinist can't be accurate, it just takes more time to be more accurate and time is money. The 3.0" part will be cheaper to have made than the 3.000" part.
. Since a machinist is used to working with close tolerances, a 6" part will most likely be a lot closer than +/-0.5", but, by the specs given, 5.503" would be a good part.

As I said to Westfw, then it is his definition and perception of the differences of the numbers, not the reality of there being no difference at all that creates the difficulty. ;-)

. If things could be made and measured exactly, then, yes, there would be no difference. . I guess it boils down to shorthand. 2.00" is easier to write than 2", +/-0.005".

I haven't any quarrel with any of this at all, just trying to explain that my perspective does not show me any difference, because I do not accept 2", +/- 0.005" as = 2" But, if I can not make something to those specs, then it still doesn't make a difference to me ;-) Even back when I helped a friend of mine bore out a cylinder for my VW bus, and regrind the valves, 0.005 tolerances were still written in whole numbers if only zeros followed it. Maybe I am just stuck in the past on this one ;-)

Hear, hear.

I think it would be cool to make one for every day of summer :D

Pogs were round though, IIRC (the innards of the POG bottle caps originally; before commercialization). At least, these are hand made......but since there is no limit on what can be made in the size restriction of 1" x 1", I have a few ideas of my own :-) ...as soon as I post my most recently finished (simple) project. ;-)

Actually, it was an idea for school - a colleague is retiring at the end of term, and I'd been racking my brains for a unique gift - I'm going to get the kids to make inchies and then present her with a giant collage!

(Your links are full of warnings of addiction)