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

Select nut size or choose Custom

Trap Type

Select the type

Printer Tolerance

Acceptable dimensional 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.