About the threaded containers

Size the jar, and the lid follows

Set the inside diameter and inside depth of the space you want, and the walls, thread and lid are built around it. The lid is made from the jar’s own thread, offset by the clearance, so the two are the same helix and a lid made here always fits a jar made with the same settings. The outside of the jar and the lid come out the same width, so the lid sits flush. You can print both together (side by side on one plate), or just the jar or just the lid.

The thread

• Thread pitch is how far the lid travels in one full turn. Coarser (4–6 mm) threads print more reliably and go on faster; finer ones hold better but need cleaner printing.
• Thread turns is how many turns the lid takes to close. Two to three turns holds well; more takes longer to open.
• The thread has 45° flanks with flat crests and roots, so it prints without supports, unlike a standard 60° thread whose lower flank overhangs too far. It is a right-hand thread: turn the lid clockwise to close it.
• Thread clearance is the gap between the jar’s thread and the lid’s. It is the one setting that depends on your printer: too small and the lid binds or won’t start, too large and it wobbles.

Tune the fit first

Print the Thread fit test preset, a small jar that prints in under an hour, and screw the lid on. If it is too tight or won’t start, raise the clearance by 0.05–0.1 mm; if the lid is loose or wobbles, lower it. Once it turns smoothly, use the same clearance for any size: the fit doesn’t depend on how big the jar is.

Printing

• Orientation: the jar is printed upright and the lid flat-top-down, as they are laid out, and neither needs supports.
• Settings: a 0.4 mm nozzle, 0.12–0.2 mm layers and at least three perimeters. Slower outer walls give cleaner threads.
• Grip grooves around the lid’s edge make it easier to turn; set them to 0 for a smooth lid.

FAQ

Is it airtight or waterproof? No. The threads make the lid screw tight; they don’t seal. For liquids or to keep air out, add a silicone gasket or a layer of tape under the lid, or print the lid in a flexible filament with a rim.

Can I keep food in it? It is fine for dry goods like sweets, spices and buttons. Printed plastic has gaps between layers that can hold residue, so hand-wash it, keep it away from the dishwasher and heat, and use a food-contact filament if it matters to you.

Why won’t my lid start? Usually the first layer is a little wide where the thread starts. Raise the clearance by 0.1 mm, or clean the lid’s first thread with a small file or a turn of sandpaper.

Why does the page say the inside depth is too small? The neck that carries the thread is as tall as the turns times the pitch, and the jar needs a few millimetres more below it. Use fewer turns, a finer pitch, or a deeper jar.

Can I make a bolt and nut? Not yet: this makes jars and lids.

Can I edit it in CAD? Yes: the STEP button gives an exact model of the jar and lid as two solids, with a true helical thread that mates exactly as it does in the STL.