Are original vex parts wrong?

I recently found that some original vex parts are probably designed wrong.


This is original 1x3x1x35 Aluminum C-channel from .
Vex uses 0.046 inch material thickness in steel, and 0.064 inch in aluminum parts. According to my calculations, this part should be 0.564 inch from the ground to the top. But is not.
I know these differences are so small in real life, but when designing, parts are not perfectly fitting, which is very annoying.

Does anyone know something about this?

(I am using Autodesk Inventor Professional 2020)

What calculations tell you that this part was “designed wrong”


First, i measured the parts that we used in our robot,

I compared the steel 1x5x1x25 C-channel and and aluminum 1x5x1x25 C-channel.
On the right, the aluminum c-channel fitted perfectly but on the left side, you can see that steel c-channel is not fitted perfectly (the blue are is overflowing).
I first noticed this when i was trying to connect parts, but i didnt because parts are not ftting perfectly.
Unfortunately, i can’t compare the aluminum 1x3x1x35 c-channel with steel because there is no steel version.
(The both parts are from

Where did you get the 3D files from? They could be from VEX, or they could be made by someone else, who measured physical parts.

Parts vary slightly, there isn’t such thing as a physical piece that matches perfectly to the 3D model, just go through all the pieces you have and see which one varies the way you would like it to.

The difference seems so smaller that you could hit it with a hammer a few times and that would solve it. (I feel like this would be a good idea in theory and a bad idea in practice, but you don’t know until you try! :grinning_face_with_smiling_eyes:)

I get the CAD files from official site of VEX ( Actually there is no problem in real parts but in design, these small differences are enough to annoy you much :stuck_out_tongue_closed_eyes:.
If there is a CAD library that all of the CAD files are fine, then it will be great!
(btw thanks for the recommendation :grinning_face_with_smiling_eyes:)

I have been using Autodesk inventor 2022 with This library and have not had any problems with parts being off.

Even if you design something to be perfect, it wont be. CAD is where everything is perfect and the majority of the time you cant reproduce it perfectly. Keep in mind even though the CAD model may say something different, I would make a big bet the tolerances on these parts is big, meaning one part is probably not going to have the exact same dimensions as another part.

At least most of those issues are also fixed in the VEX CAD Fusion 360 Library

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