[Solved] Dimension mm - inch

[Rantanplan7]

Hi everyone,
since a couple of days I have now the e-book and it was helping in many small bits and pieces
However there is one thing which I can't understand why QCAD is doing this.

My standard unit is mm, so everything is set to mm. Sometimes I have to do a dimension in inch or mm/inch. After Husky told me about the ability to write something after <> mm I thought it should be easy. So I made the drawing, put the dimensions on them and wrote the mm value after the two symbols <> 1250 mm. Now as I don't like to calculate the feet/inches from my mm I just changed the drawing settings from mm to inch and the dimension settings from dezimal to technical and I get 104' - 2" 1250 mm. Alright everything ok, but after I tried to print the drawing I end up in a mess.
My drawing is shrinking and off the drawing sheet....
I simply do not understand what is happening here. Any suggestions?

MM_inch.jpg (130.51 KiB) Viewed 16205 times

[Husky]

Hi,

My drawing is shrinking and off the drawing sheet....
I simply do not understand what is happening here. Any suggestions?

Did you change the drawing unit or did you convert the drawing unit?
The result of changing the drawing unit means e.g. a 100 mm line is now 100 inch. Just a different Name ...
The result of converting the drawing unit means e.g. a 100 mm line is now 3" 15/16 and the drawing is properly scaled etc.

I get 104' - 2" 1250 mm. Alright everything ok

This measurement/info makes no cense to me. I assume you changed only the unit.
Why? 104' - 2" 1250 mm = 31750 mm - 1250 mm

[Rantanplan7]

Alright, and yes I didn't convert the unit.
When I do that I get a problem with my library as all items are not automatically converted.

Here is what I would normally do - after I have made a drawing and put all dimensions on it I would like to get the feet/inch values so I thought it is easy to write the values I can read like <> 1250 mm and after converting I get automatically the calculated feet/inch values in front of it.
This works now but I cannot use any item from the library afterwards.

I will work vice versa instead so I convert to inch write the inch value behind the <> and convert back to mm.
Any other clever way to do this?

[Husky]

Alright, and yes I didn't convert the unit.
When I do that I get a problem with my library as all items are not automatically converted.

Are the items saved in the library with a unit like mm or they saved with unit "none"? QCAD needs a unit to calculate the conversion.

Here is what I would normally do - after I have made a drawing and put all dimensions on it I would like to get the feet/inch values ...

Is the smallest number always a full inch? Never a fraction of an inch? I don't know exactly what your drawing is about but that sound like walking on thin ice ...

[Rantanplan7]

Oh, I have not recognised that it is possible to save library items without a unit. Unfortunately they are all without a unit. So I assume that is the trouble maker? I have to save all library items with a unit?

[Rantanplan7]

I have just tried it.
Surprising that QCAD is allowing to save a drawing without a unit. Wouldn't it be good to get a message to avoid this?
To create the library items I was opening all items in Autosketch, saved them as dwg file, opened the file in QCAD selected them one after the other and saved them as library parts.

[Husky]

Surprising that QCAD is allowing to save a drawing without a unit. Wouldn't it be good to get a message to avoid this?

No. Usually the CAD wold is always in "none". QCAD has this as a special feature to be able to convert units.

... opened the file in QCAD selected them one after the other and saved them as library parts.

If you are already doing that make also sure that the "Measurement System (for line types and hatch patterns) is set to the correct system - avoids headache in the long run.
e.g. Drawing Unit mm = metric, Drawing Unit inch = imperial

Husky-2017.12.22-01.png (9.88 KiB) Viewed 16183 times

[Rantanplan7]

So, now there will be a couple of weeks christmas break in using QCAD
I wish you Husky and Andrew and all the others here in the community a merry christmas and a good start into the new year

[Husky]

So, now there will be a couple of weeks christmas break in using QCAD

From time to time there are hard times in our life ...

I wish you Husky and Andrew and all the others here in the community a merry christmas and a good start into the new year

Thank you very much! Happy Holidays and a wonderful 2018 to you too!

[Rantanplan7]

Hi Husky,

as I'm converting more drawings for colleagues in the States I have more trouble with this.
I still work in the metric system with mm and I'm used to convert a drawing to inches, to get the feet-inch dimension values.
But, very strange, and without a visible logic behind it, some library blocks (after I have converted the drawing) are scaled correct, and some are by far to huge (I assume 1:1 - and my sheet is 1:50).
Now I took a close look on two library items - one correct size, one too large, they are both stored with drawing unit - none but behave different. When I store them both with drawing unit - mm they are both correct.
Now the solution is to save all 300 items with the drawing unit set to mm? Or would I get some new problems in the future by doing this?

[andrew]

Drawings with unit "None" are inserted without conversion. I.e. one unit is inserted as one unit, no matter what the unit of the drawing is. This can be used for unitless components such as diagram items or symbols.

If the library items are parts with a real world representation, setting the unit makes sense.

[Rantanplan7]

Thanks Andrew.
So I have someting to do now.
And I will make sure that I will keep an eye on that whenever I create new blocks for the library.

[CVH]

Hi Rantanplan7,
I think we need an example file with a good and a bad, one before conversion, on after.

A) I am aware a document has a unit.
B) Can't include library's in a file, only a copy as a block unrelated to the library item.
C) Common library items are simple dxf drawing, again a document, again with a unit.
D) To be usable 'as is' in both systems, some/most library items have the unit none.
E) Can't find the unit of a block, it doesn't has one.
F) Once a library item is inserted as a block it has no unit of its own, only that of the drawing.

The problem is that eg. a line 10 long in a library item (unit none) inserted in a document is
10mm long in metric/mm and 10 inch long in imperial/inch. But also 10m in metric/meters.

The question now is does Qcad convert units inserting library items with a unit?
So I found an exception on the rule you stated:
Misc .. Bath plan.dxf is in unit mm: 1700x725mm.
Inserted in an inch drawing it is 66.929.. by 28.543..
That seems correct from my point of view.

Next also remember that once a block exist in a drawing,
inserting the same library item, a block with the same block name, doesn't overwrite that block.
This doesn't obey correctly if the drawing is converted in units meanwhile and the library unit is off or none.

Meanwhile Andrew confirms this story.
The next question would be: why eg. M4x10_DIN84_f.dxf has no unit?
M4 & DIN84 >> mm ... Isn't it?
It works for Bath plan.dxf
That are very big screws compared with the bath.

Regards,
CVH

[Rantanplan7]

Hi CVH,

thanks a lot. A bit sad but however after 3 years I understand this problem now.
The reason that I have not recognized earlier what is going on is that I'm almost all the time work only in mm - and in that case I had never a problem.
Now in the last days I have to work a bit more with inches, so I get the trouble with my items with no unit.
Your explanation helped a lot to understand the secret behind it - I wasn't diggin deeper - just thought "no idea what QCAD is doing here" my symbol was jumping from 400 mm to 33' 4'' and I have not calculated how many inches 33 feet are. In that case I would have seen that my 400 mm just got 400 inches as you explained it....
If you ever plan to come close to Heidelberg in Germany just give me a note and I would like to invite you to a beer and have a chat.

Best regards

Sven

[CVH]

Still, my question is out.
We use scaled imperial sized things in a mm drawing if that part only comes in imperial measurements.
Like a Swagelock valve or pipe-fittings in inches.
Same as an imperial user should be able to use a metric part.
Like a M4 screw on a bathtub or a Bosh part

About the invitation: Thank you very much, but for the moment I'll consume it here.
You may always PM me.

Regards,
CVH