## Turbo Talk => General Discussion => Topic started by: 3acorns on February 13, 2013, 06:53:33 AM

Title: When is 5.625 not 5 5/8
Post by: 3acorns on February 13, 2013, 06:53:33 AM
I am having problems with getting correct sizes in my objects.

Lets say I lay out a rectangle as 7 5/8 x 7 5/8" -  these are the characters I type into the inspector bar

In the inspector bar it shows up as 7 5/8".

Then, as I do my drawing, I lay out 2 parallell constrtuction  lines that are set at the vertex of this rectangle.

Then I measure the distance between the construction lines  and check it in decimal format. Guess what, the distance is NOT 7.625 it is 7.6008!

Whats up? See images
Title: Re: When is 5.625 not 5 5/8
Post by: GregT on February 13, 2013, 07:27:14 AM
Post the drawings... makes it easier to give an answer.
Title: Re: When is 5.625 not 5 5/8
Post by: 3acorns on February 13, 2013, 07:30:12 AM
you mean the tcw file?
Title: Re: When is 5.625 not 5 5/8
Post by: wd on February 13, 2013, 07:34:39 AM
you mean the tcw file?
Yup!!
Title: Re: When is 5.625 not 5 5/8
Post by: 3acorns on February 13, 2013, 07:47:56 AM
OK Here is an example!
Title: Re: When is 5.625 not 5 5/8
Post by: GregT on February 13, 2013, 07:52:24 AM
Set the precision for your drawing higher. Your rectangle is not 7 5/8... it is actually 7 615/1024... or 7.6006122605.
Title: Re: When is 5.625 not 5 5/8
Post by: wd on February 13, 2013, 08:37:14 AM
If use the TC icon as default instead of 1/5 in the inspector bar and the precision in space units to six it should properly read in the measurement palette.The Page Set Up Wizard on a fresh new drawing in settings for Fractional Precision set to 1/64 will help avoid scenario
Title: Re: When is 5.625 not 5 5/8
Post by: 3acorns on February 13, 2013, 08:51:08 AM
Well OK I will do this .. It is not intuitive from the inspector bar that this is going to happen. with precision set to 3, the help says that

"Precision: The number of decimal digits. For Fractional or Architectural units, Precision determines the accuracy of the denominator, in powers of two (1=1/2â€, 2=1/4â€, 3=1/8â€, etc.)."

at this leads me to think that if I am entering in 8ths (with a precision set to 3) as in 5-5/8, then it would use an "exact" value.

5 divided by 8 is .625 exactly, but it appears that the program is saying that I am going to lay in a line that is accurate to within 1/8 inch. So, the line I am going to give you is going to be within 1/8 of what you specified.

Interesting that when I type in 7-5/8 the program lays in

not 7 5/8... it is actually 7 615/1024... or 7.6006122605

strange that 7 5/8 is seen as 7 615/1024 ( that 1024 is a power of 2 thing mentioned in the help text)
Title: Re: When is 5.625 not 5 5/8
Post by: GregT on February 13, 2013, 09:04:52 AM
When I type in 7-5/8... TC give me exactly  7-5/8. It will give you  7-5/8 if you type in  7-5/8... no matter what you have the precision set to.
Title: Re: When is 5.625 not 5 5/8
Post by: Cliff on February 13, 2013, 12:17:08 PM
your round off was set to zero in dimensioning.
Duno if that matters, but I prefer to have some zeroes in there on the right of the decimal and left of the 1.
Title: Re: When is 5.625 not 5 5/8
Post by: 3acorns on February 13, 2013, 12:33:59 PM
Cliff, yeah I change that sometimes especially if I am doing machine drawings
Title: Re: When is 5.625 not 5 5/8
Post by: wd on February 14, 2013, 09:14:08 AM
After careful study the conclusion is that the line is actually what is in the Measurement Info palette which is accurate.If lines were accurately space it would reach the quadrant to have the line measure at 7.625.Still fuzzy and confused move the line to the right .0244 using delta x than take the reading at Inspector bar and Measurement Info palette.You may have snap to the wrong vertex or the point in the dimension line giving you the wrong reading.Changing it to from Default to 1/5 won't make difference.See attach screen shots.
Title: Re: When is 5.625 not 5 5/8
Post by: 3acorns on February 14, 2013, 09:29:54 AM
WD

You are seeing the same fuzzy that I am.

This started when I made my "box" ( Actually a Concrete Block which is manufactured at 7 5/8 x 16 5/8) by  typing in the size to the inspector bar. I typed 7 5/8. Then, when I went to make the face of the box line up with something else whose size had been typed in as 7.625, I found that the construction lines on these 2 object did not line up.

Then I checked the measurement info and saw that the lengths of the objects were different. and I agree that the measurement info gives the corect reading and value of what the size "really" is.

That is what caused me to feel that in TC a setting was making it so that 7 5/8 is NOT 7.625!  ie that typing in 7 5/8 as a size can result in something different than typing in 7.625 as a size.

My test drawing that I sent to the group was made by typing in the values and not dragging or clicking to any vertex etc. and it shows the surprising occurrence. I think you are right that the precision is interacting with the division of 5/8 and yielding the "Aw what the heck,  .6002 is close enuf to .625!"

This, to my engineering pea brain, is contrary to 5/8 ALWAYS dividing to .625
Title: Re: When is 5.625 not 5 5/8
Post by: Alvin Gregorio on February 14, 2013, 10:45:06 AM
WD

You are seeing the same fuzzy that I am.

This started when I made my "box" ( Actually a Concrete Block which is manufactured at 7 5/8 x 16 5/8) by  typing in the size to the inspector bar. I typed 7 5/8. Then, when I went to make the face of the box line up with something else whose size had been typed in as 7.625, I found that the construction lines on these 2 object did not line up.

Then I checked the measurement info and saw that the lengths of the objects were different. and I agree that the measurement info gives the corect reading and value of what the size "really" is.

That is what caused me to feel that in TC a setting was making it so that 7 5/8 is NOT 7.625!  ie that typing in 7 5/8 as a size can result in something different than typing in 7.625 as a size.

My test drawing that I sent to the group was made by typing in the values and not dragging or clicking to any vertex etc. and it shows the surprising occurrence. I think you are right that the precision is interacting with the division of 5/8 and yielding the "Aw what the heck,  .6002 is close enuf to .625!"

This, to my engineering pea brain, is contrary to 5/8 ALWAYS dividing to .625

I don't think it's TurboCAD doing anything*.

When I open up your drawing, and do nothing more than place a line right over the top of your line by: Snapping to the left vertex of your line (as a starting point), then typing in a value of "7 5/8", and an angle of "0", my line is indeed the correct length- a bit longer than your line, and all the way over to the edge of the circle.

*Edit: I mean, one of the things we have to ask ourselves is:  If it's TurboCAD that's messing up, then how was the other line (the vertical 15 5/8" line) drawn, and is drawn to the correct length?  And try as I might, I can't replicate what you are describing as the TurboCAD error; I am consistently getting a 7.625" (exactly- no more, no less) when I create a line by entering a value in the Inspector Bar of 7 5/8. There has to be something that you are inadvertently neglecting to communicate to us regarding how the 7 5/8" line was drawn; has to be.

-Alvin
Title: Re: When is 5.625 not 5 5/8
Post by: 3acorns on February 14, 2013, 05:35:18 PM
Alvin -- I was just testing you! :P

I misspoke. :(  I had laid in the object by dragging to the size I wanted. I clicked to start the rectangle, then dragged the other vertex of the rectangle till it "got" to 7 5/8 x 15 5/8. How did I "know: it was the right size?  Well, I looked at inspector bar as I was dragging and that it the value shown in that inspector bar.

MY BAD for misstating what I did :-X, and double MY BAD :'(  for using the "drag to size" for laying in objects.

Here is my write up that I made as you were making your post ....
****************
OK, after further investigations I see that using the drag to size technique is a really really  bad idea.

Why? Because what the inspector bar is saying about the "size" of you object as you are laying it in is not really the size of the object.

Try this.

Set up and show a grid with 1/2" spacing of the gridlines. Set the precision to "0" and the units to fractional, then drag, starting at a grid intersection, to make a box or a line. You will see that after you drag to your desired size, you can still drag the object size, and the inspector number will not change until you exceed a value based on the precision setting. You can dink around with moving the cursor and the number stays the same.

A precision of 0 is to the nearest 1/2 inch, which in practice means that if you start a line and start dragging, the inspector value will stay at 0  ..... until you cursor past a length of 1/2", and then, it will jump to saying "1" even though the cursor is actually at 1/2 or 5/8 or 3/4 etc. Check it out  .... you can drag that endpoint of your line anywhere in between the "0" gridline and the next gridline (1/2") and that inspector value will not change.

So... if you have your precision set too low and you DRAG to 7 5/8 and then hit enter, although you may think you have just laid in a line 7 5/8" line, you may or may NOT be getting that.Indeed, you likely are NOT getting that length.

The same works for the measurement feature, so if you are measuring something in fractional units then the value that is displayed only is accurate to what your precision setting is set to.

Try it . Set up a grid where the lines are at 1/2" apart. Now, measure  the distance between 2 adjacent gridlines and see what it says the distance is. You will find that it "says" the distance is 1......" but you just did a gridpoint to gridpoint of 2 gridlines that are only 1/2" apart.

Bottom line -- ALWAYS type in the value you want. Don't rely on the "Drag to Size" feature ... even if your precision is set to some high value. The only way to lay in a line and have it be the dimension you want, is to type in the value of the length.

That being said, we also have to be careful of using the drag to place method of laying in construction lines parallel to existing lines, because the inspector bar will not show the true position of the new line either. If you want a construction line laid in a 1" offset from an existing line, then type in the distance, do not use the inspector bar value displayed to lay it in.

Addendum: Don't rely on the inspector to give you the true size of a selected object either... unless you are SURE you created the object by typing in the dimensions/sizes, or unless you are sure it was created off of objects created in an exact manner and created by using parallel construction lines that were NOT laid in by dragging.

Title: Re: When is 5.625 not 5 5/8
Post by: Alvin Gregorio on February 14, 2013, 05:50:07 PM
[text omitted]
****************
OK, after further investigations I see that using the drag to size technique is a really really  bad idea.

[text omitted]

That being said, we also have to be careful of using the drag to place method of laying in construction lines parallel to existing lines, because the inspector bar will not show the true position of the new line either. If you want a construction line laid in a 1" offset from an existing line, then type in the distance, do not use the inspector bar value displayed to lay it in.

In all my years of using TurboCAD, it never, ever occurred to me to try to drag something to a size; I've always inputted.  [EDIT:  That is, when accuracy is something I'm shooting for/desire; I drag-to-resize often, but only when I don't care about accuracy or exactness.]  I guess if one were just sketching at first- conceptualizing- then they might be tempted to drag to a new size- just "click"-and-"drag"-and-"un-click"; I guess.... but I've never, ever been tempted to do it that way.

----
The test you described (quoted above)- and the results you reported- seem just so intuitive to me that I would have always just sorta' known and expected the results you're reporting.  Not saying I'm of some super-intelligence or anything; but it just goes to show you how once our individual brains see something a certain way, it's difficult to see it another.

----
I knew there had to be something that you were omitting to tell us regarding how those lines were created.

Looks like you have it handled.

-Alvin
Title: Re: When is 5.625 not 5 5/8
Post by: 3acorns on February 15, 2013, 05:28:31 AM
[text omitted]
****************
it just goes to show you how once our individual brains see something a certain way, it's difficult to see it another.

----
I knew there had to be something that you were omitting to tell us regarding how those lines were created.

Looks like you have it handled.

-Alvin

Thanks for nudging me in the right direction to ferret out and understand what it was that I was doing that created the result I was getting, and to understand what is going to happen if I do certain thing certain ways in TC and to train me NOT do do certain things.

As far as the intuitive reasoning, mine was the opposite of yours. When I type 7 5/8 into the inspector bar, what I see in the inspector bar is 7 5/8. When I drag a line "to 7 5/8", it says exactly the same thing in the inspector bar that it would say as if I had typed it in. Then when I hit tab - tab and then enter, (to lay in the dragged line), that inspector bar still says the exact same as if I had typed it in. To me, then 7 5/8 should always be 7 5/8, but apparently it is not.

To make matters more squirrelly, the TC help says this in the Inspector Bar entry ....
Quote
When moving the cursor to position or size an object, the values in the fields update dynamically.

My Comment  ....Yeah, they sure do update dynamically, but those values being shown are NOT the true values, and so that creates the kind of situation that makes space shuttles blow up. Not only do they not show the true value dynamically, they do not always show the true value statically. For example, if I am a machinist contractor and I got your TC drawing to make a machine part, then unless I knew that each and every object you drew was actually typed in, I could not trust your drawing.

Going further  in the Measurement Help it says
Quote
Measures the distance between two points, the cumulative length between additional points, or the length of entire objects (perimeter).

1.   Select two points to define the distance you want to measure.
The distance and deltas in X and Y are listed in the Measurement Info Palette.

Here is what is should say
Quote
Measures the distance between two points, the cumulative length between additional points, or the length of entire objects (perimeter).

1.   Select two points to define the distance you want to measure.
The distance and deltas in X and Y are listed in the Measurement Info Palette - but only given to an accuracy based on your settings for Precision in the drawing Space Units setup. This can give unexpected results, in that for example if your line was created by typing in a value of 1 3/8", and your precision is set to "0", then the value displayed in the measurement window will be "1" Not 1 3/8.[/quote]

Anyway, thanks again for helping me understand the behavior of the program. :) If you had not been so helpful I would have created my own exploding rocket. As it was, you helped me find that loose heat shield tile and replace it before my rocket went into production.
Title: Re: When is 5.625 not 5 5/8
Post by: murray dickinson on February 15, 2013, 06:47:58 AM
I know that the notion of actual training rather than winging it from the help files is increasingly regarded as ridiculously old school, but machinist contractors don't scale off drawings, they read dimensions, which will be accurate if the program's features, like parameter entry, snaps, and constraints, are used.   Sheets of paper change size with humidity.
Title: Re: When is 5.625 not 5 5/8
Post by: 3acorns on February 15, 2013, 08:07:08 AM
I wasn't meaning scaling off plans I was meaning looking at the print and seeing what the dimension line says the dimension is.

The accuracy of the dimensions that are printed on the plan and delivered to the machinist cannot be known, unless he knows what precision the guy doing the drawing had set on the Dim Tool as he was dimensioning the part. The true Turbocad size of a part whose  dimension "says" 1/8" may or may not actually be 1/8" and can cause Murphy to enter the picture and start causing problems.

I attach a drawing that demonstrates this. Each of the squares has had the horizontal part of the box dimensioned by tcad. The Dim Units Tolerance Precision setting was "3". The Space Units of the drawing was at "0".

Note that each dimension says 1/8". Zoom in on the objects, all of which have their left side set at the same vertical gridline. See that each box is actually a different real size. Only the top box has a true size on the horizontal of 1/8". The one below is a bit bigger and the other a bit bigger still, yet each has been dimensioned by TurboCad as 1/8".

If the designer is not aware that the dimensions that he is laying in are "off" (in an amount governed by the precision value), he is gonna be in for a big surprise when his machined parts do not fit and machinist says " Hey your part was "made to print" , and it was you, not me,  who dimensioned the part. It isn't my problem that your settings on an object that is really 39/256", gets dimensioned as 1/8" because the Dim Units on your Dimension Tool was set to 3 instead of 8. If you would have dimensioned it as 39/256" I would have made it to that.  I simply made it to what you said.

Lesson(s): Designers  ....Always check and recheck the Dim Units/Tolerance Precision setting on the Dimensioning Tool, and Always Check and Recheck your Drawing Space Units Precision Setting, And NEVER drag and use the value displayed in the inspector bar to size an object and NEVER drag (and use the value displayed in the inspector bar) to lay in a parallel construction line.

Machinists ... Get in bed with the designer so you can trust that he has not had a brain f&^t

Idea for future Releases Provide a way for a designer to "lock" the Precision Settings so that it requires a password to change them.

[EDIT] and make it so that if I change the dim precision it updates all the previously laid in dimensions to that precision
Title: Re: When is 5.625 not 5 5/8
Post by: Alvin Gregorio on February 15, 2013, 08:46:47 AM
I wasn't meaning scaling off plans I was meaning looking at the print and seeing what the dimension line says the dimension is.

[text omitted]

Lesson(s): Designers  ....Always check and recheck the Dim Units/Tolerance Precision setting on the Dimensioning Tool, and Always Check and Recheck your Drawing Space Units Precision Setting, And NEVER drag and use the value displayed in the inspector bar to size an object and NEVER drag (and use the value displayed in the inspector bar) to lay in a parallel construction line.

Machinists ... Get in bed with the designer so you can trust that he has not had a brain f&^t

Idea for future Releases Provide a way for a designer to "lock" the Precision Settings so that it requires a password to change them.

[EDIT] and make it so that if I change the dim precision it updates all the previously laid in dimensions to that precision

I'll make one suggestion to you/for you 3acorns, then I'll be off this Topic thread:

You might like to create a TurboCAD Drawing Template and in your Options|Preferences Setup, select to always start New drawings with that Template.  If not familiar with how to create and use drawing Templates in TurboCAD, search the on-line or your User Help pages- or even here, on this Forum.

In your Template (.tct), you can set the Drawing Setup Precision as high as you wish (up to something like 1/1024", I believe), and have a pre-set Dimension Style within that TurboCAD Drawing Template file that is as precise and rounded-off as you and your theoretical potential machinists doing manual and/or CNC fabrication work would desire.

-Alvin
Title: Re: When is 5.625 not 5 5/8
Post by: 3acorns on February 15, 2013, 09:14:16 AM
Great Idea!

Don't be a stranger. You have a good take on things.