A nut trap is a hexagonal pocket printed into a part that holds a standard hex nut captive. When a bolt is threaded into the nut, it creates a strong mechanical connection. Nut traps are stronger than printed threads.

How much clearance should a nut trap have?

Add 0.2-0.4mm total clearance (0.1-0.2mm per side) to the nut width. The nut should slide in with a firm push but not fall out freely. Too tight and the nut will not insert; too loose and it will spin instead of tightening.

Should I use a drop-in or slide-in nut trap?

Drop-in traps (printed with a bridged roof) work for nuts inserted before the pocket is closed. Slide-in traps have a side slot to insert the nut after printing. Slide-in is more versatile but slightly weaker.

How do I prevent the nut from spinning?

Make the pocket a tight hex shape that prevents rotation. Add a slight interference (-0.05mm) on the flat-to-flat dimension. You can also add a small bump or ridge on one flat to lock the nut in position.

3DPrintCalcs

Nut Trap Calculator — Hex Pocket Dimensions

Design hex nut traps with correct pocket dimensions and depth.

Nut Size

Trap Type

Printer Tolerance

How We Calculate This

Nut Trap Dimensions

Pocket width = Nut width (across flats) + 2 x Tolerance + 0.1mm
Pocket depth = Nut height + 0.3mm clearance
Bolt hole = Bolt diameter + 0.4mm + Printer tolerance
Corner radius = 0.4mm minimum (FDM limitation)

The pocket is designed as a hex shape using the across-flats dimension. FDM printers cannot create perfectly sharp internal corners, so a small corner radius is applied. The depth includes clearance for easy nut insertion.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.