This cap “lock” is meant to deter and prevent any unauthorised personel from accesing the insides of your container - without the knurled handle/"key" inserted, outer cylinder rotates freely on a ball bearing, preventing others from unscrewing original cap, glued to the inner part.

It is a remix of Kit's Milk Bottle lock - i needed version for a different container with wider screw cap (46.5x10mm), but ended up redesigning the whole part. It was designed to incorporate hardware that i actually had laying around - thats why it uses some odd components like M2,5x20 screws or 688 ball bearing. Feel free to modify attached STEP files to your needs :)

Hardware needed:

• 2x M2.5x20 screws or nails
• 1x tapered head M3x16 screw
• 1x M4x8 washer - it is intentionally bigger than screw - this way the head is slightly recessed and takes less height
• 1x M3 nut
• 1x 8x16x5mm (IDxODxH) 688 bearing
• your favourite plastic glue

Important:

M3 nut in rotating part and bearing in cap part needs to be inserted while printing - add print pause in your slicer on the last layer of the recess.

Use some glue for locking the M3x16 screw and check whether both cylinders rotate freely against each other before gluing cap in place. According to your printer capability and slack in the bearing, you might need to print both parts with wider gap or use some grease - otherwise the lock might be defeated without the key, by tilting or applying pressure to the rotating part.

Printer:

Prusa MINI

Resolution:

0.15mm

Perimeters:

3

Supports:

No

Filament:

DevilDesign PLA