How to measure for perfect fits for 3D printing

[Printenator]

I’m trying to 3D print a custom organizer for my tools, but my first batch was a total expectation vs reality moment. I used calipers and Shapr3D, but only 1 out of 3 items actually fit!
The blade container is way too tight, the box cutter won't go in at all, and somehow the weirdly shaped scissors fit perfectly. I’m using a Bambu Lab A1, so I know the printer is precise, the issue is definitely my measuring game

How do you guys handle measurements for irregular shapes? And how much clearance (tolerance) should I be adding to my models so things actually slide in and out smoothly?

 

[Kirkis_Elf]

For weird shapes, I cheat. I trace the outline in Shapr3D using a photo or I do a quick test print of just the “hole” section first. Printing a small fit test saves a lot of wasted filament on a full organizer.

 

[Mrgrta_sour]

Just put the parts on a flatbed scanner next to a ruler or some graph paper.
Once you scan it, import the image into your software, scale it to match the ruler, and you've got a perfect template to trace over.

 

[Adam Anderson]

For tight fits, I generally go with 0.050", and for loose fits, I go with 0.100".
When I am designing cutouts for tools, I generally go with the simplest geometry required to contain the tool. For a box cutter, I would just use a rectangle of basically the bounding box for the tool.
For something like scissors, I might do two bounding boxes, one for the blade and one for the handles. I find that this can also help leave room for you to get your fingers in there and grab the tool out.