Please help me understand why the dimensions on my drawing seem incorrect to me.

Pahl

Here is a drawing I found online that I'm working with as a exercise.



I can create the model with the correct dimension but I'm having trouble getting these three dimensions to display correctly on my drawing.






When I go to create the drawing this is the best OS seem to do.





How do I correctly display them three dimension on my drawing?


Edited to add:

I see how to manually add the dimension to show what ever I want, but shouldn't OS be able to automatically display these three dimensions like it does for the rest of the dimensions on my drawing?



Here is my model.
https://cad.onshape.com/documents/941b9c69311c0ca8e4886864/w/eab2e84dcc88f6a53636bf92/e/e3d7e0d8bc934967d0973f5d

Here is my drawing.
https://cad.onshape.com/documents/941b9c69311c0ca8e4886864/w/eab2e84dcc88f6a53636bf92/e/41b369c67afd6c09d2d284cd

Thanks!

jakeramsley

Dimensioning in an isometric view gives you the projected lengths onto the sheet, not what the model dimensions are.  If you were to print it to scale and measure those lines with a ruler, you would be getting 16.9, 13.85, and 6.96 as the length of the lines.

Pahl

Hi Jake

Ok, that makes sense. How would a professional go about showing these three dimensions on a drawing for this part?
Maybe the 17x17 as shown on the original image I'm trying to work with has the dimensions displayed incorrectly to start with? 
Would a professional drawing normally even include dimensions on the isometric view?

Thanks,

NeilCooke

Hi Pahl, no a professional drawing would not dimension the isometric (maybe occasionally for clarity). You would create at least 2 projected views and an auxiliary view of the face that has the cutout in it.

Pahl

Hi Neil,

Good to know, thanks!

PeteYodis

@Pahl When drawings typically show dimensions on an isometric view, those dimensions are called "True" dimensions.  This distinguishes the dimension from a "projected' value as is typical in other drawing views.  We do not yet offer true dimensions in Onshape drawings.  It's not often requested for the reasons Neil cites.  There are circumstances where the "true" dimension might be preferred, but usually you can create a view of your geometry where the projected value is what you want to show.

Pahl

Hi PeteYodis,

True dimensions, good to know. This is just a hobby for me, but I really want to be as professional as I can about it.

I started out wanting to learn CAD for 3d printing. Started with SketchUp. After 30 days of working with SketchUp I purchased my first 3d printer.
Shortly after that I ended up coming across Fusion 360. From there I worked with Fusion 360 for about six months before I come across OnShape.

So that's been my limited experiance with CAD so far, but I have to say that I'm very impress with OnShape. I don't know if CAD can be a hobby itself as I started out thinking I was going to be getting into the 3d printable hobby craze and CAD would just be a tool I use for it, but I enjoy the CAD side of things probably 10x more then the printing part of it as of now. Maybe I need a better printer haha.

Thanks again for OnShape and keeping it free for guys like me. 

billy2

Are you kidding me? Professional? That's not a reason not to have true dimensions for an ISO view. Not everyone (architects) know 3rd angle projection & engineering documentation. 

Make a quick drawing to have something built, why not have them? 

Are you kidding me?

steve_shubin

DIMENSIONS ON ISO - It’s been used, maybe more than some realize

The world’s leading residential construction hardware company, Simpson Strong-Tie, has been using iso dimensions for decades. I remember their 3D drawings with dimensions being used back in the late 1970’s / early 1980’s

You used to walk into any lumberyard or construction hardware store, and there would be a stack of Simpson booklets with their easy to decipher illustrations

If you have the Home Depot app on your smart phone, in the search, type in a35

The A35, or as some of us old farts know it, the TECO clip, is one of the most widely used pieces of hardware there is.

I don’t think Home Depot or Simpson would mind me posting a diagram showing this example

When I was just getting into construction, an architect showed me Architectural Graphic Standards. A book with stunning drawings. This book also had a fair amount of dimensions on iso‘s. Dimensions on perspectives

Those that only deal with the learned engineering sort, maybe they don’t see much need.

Myself, I’ve long had the view that it isn’t all that bad an idea to illustrate in a way that conveys the subject matter as quickly as possible. An iso with dimensions can do that. This idea is especially nice if you have to deal with a set of plans that has a ton of details.

Evidently, Simpson long ago realized dimensioned ISO’s were going to help them better convey to the masses

Not hard for me to think those ISO’s helped make Simpson the industry leader that they are today

For any curious to see how Simpson Strong-Tie has been using 3D dimensioning for decades — download their Wood Construction Connectors Catalog, and thumb through it

Wood Construction Connectors Catalog | Simpson Strong-Tie

And for the record. I have absolutely no stock in or ties to Simpson. My only connection is being a person that has used a ton of their products

alnis

Yep, I have to agree—it might not be standards-based, but you can make casual documentation that's simultaneously clearer and more concise with iso dimensions. It's like having model-based definition on a piece of paper or in a PDF without needing a specialized viewer.

glen_dewsbury

Having used true dimension ISO views for many years I was disappointed back in 2016 when switching over that OS had not implemented but kinda thought it would come quickly with updates. This topic is not new here. There are a couple of enhancement requests going back some time. 
No question in my mind that it can provide clarity at times that is not available with flat projections for the casual user. The response I've had from professional customers has always been positive.

Giovanni_Pengue

Same disappointment here...I was looking forward to put a true dimension on ISO view to make a drawing much more clear

JanaLumi

I also would find it very useful to have the "true" measurements in the isometric view. It helps to quickly convey ideas when putting together requirements during product development stages. I have little to no use for projected values.

S1mon

Vote and/or discuss this Improvement Request:

https://forum.onshape.com/discussion/8519/support-of-drawing-dimensions-in-oblique-views-true-dimensions