The shaft seats are the right size. The coupling needs to be longer. Those are two different requirements—and a useful AI CAD workflow should keep them separate.
In this Nora3D example, a local edit extends a coupling from 50 mm to 60 mm, while its two shaft-seat diameters remain 8 mm and 10 mm. The change happens in the same CAD document, starting from the Stepped shaft coupling prototype in the template library.
Same viewing angle and image scale. Overall length changes; both shaft-seat diameters stay the same.
Extend the body, preserve the shaft seats
Uniformly scaling this model to make it longer would also enlarge the bores. Instead, we moved the upper end by 10 mm along Z, leaving the lower end in place. The middle section grew in length while the upper details traveled together.
That upper end includes a collar, a stepped bore, a radial opening, and its access recess. Selecting the whole group matters: the intended change is to move these details together, not stretch an isolated face and hope the surrounding geometry follows.
The edit adds a Move Faces feature named Axial reach, using 13 upper-end faces. The template enters the document as a body; this new feature records the local change made to it.
Check the dimensions that must stay the same
A longer silhouette shows the overall change. Measurements tell us whether the shaft seats stayed at their intended sizes.
| Dimension | Starting model | Extended model |
|---|---|---|
| Overall length | 50 mm | 60 mm |
| Lower shaft-seat diameter | 8 mm | 8 mm |
| Upper shaft-seat diameter | 10 mm | 10 mm |
Nora3D's native geometry measurements confirm the 60 mm distance between the end faces and the 8 mm and 10 mm cylindrical bore diameters. After saving and reopening the document, the extended state was measured again with the same results.
For a targeted edit, both sets of checks belong together: the dimension you wanted to change, and the dimensions you wanted to preserve.
Give AI CAD a change and a constraint
A clear way to describe the design intent is:
Extend this end by 10 mm. Keep both shaft-seat diameters unchanged.
The first sentence identifies the change. The second identifies what must survive it. This is the same practical idea behind changing one hole diameter while keeping the neighboring holes unchanged.
For me, that is where editable AI CAD becomes useful. A starting model is valuable, but being able to adapt it to a specific requirement—and inspect the resulting geometry—is what moves the work forward.
Try a local edit in Nora3D
Start with a template, identify the faces involved in your change, and name the dimensions that need to stay fixed. Then inspect and measure the result in the same model.