Bolts , Screw , Thread , Nuts and Heat Insert Into 3D Prints




in this tutorial i will test some common used ways to use fasteners with 3D printed parts , and tried some other new ways.

there is no recommendation for using one method over other as they all successful, it's up to you to choose taking into consideration cheap/expensive parts , easy , durability ,strength and available tools .

Step 1: Modeling the Testing Part

Its a simple part with some holes and cuts , you can download the .STL file from here:

Step 2: Making Thread Directly Into the Printed Part

we will use Hand thread tap ( you can find cheap one ~5$ )

you must prepare a hole smaller than the screw size , its highly recommended to make it into the model before printing and not drill into the plastic later because the fill is not always 100% and you will have no material to make thread.

thread : recommended hole size

M2 : Ø1.6mm

M3 : Ø2.5mm

M4 : Ø3.3mm

No additional parts added
Easy to do
Strong enough to hold two parts when used as enclosure
Low durability
Require extra tools

Step 3: Heat Insert Knurl Nut

"A knurled nut is a nut with a knurled outside surface. This facilitates tightening by hand (thumb nut) or secures the nut in a substrate (insertion nut)."-wikipedia

It comes with a different shapes and sizes , it must be heated to insert it into the plastic part .

We will use Soldering iron ( ~7$ will do the job ) to heat it , once it cooled down the plastic will hold it inside the part.

Knurl nuts usually cost more than normal Nuts ,so we will also try the normal Nut inserted with heat to see if its work too.

Tip: Design a hole with 0 offset , it will fit in easily once its got heated.

Very durable

require solder
Knurl Nuts cost more ( but you can use normal nuts too )

Step 4: In-print Nuts

We will try to cheat the printer , inserting a nut during the print process and the printer will continue building the layers over it .
We tested two ways , first one (print with no supports) is making a place for the Nut with flat top and bottom and 0.5mm offset on the sides . The second with 45 degree on the top to avoid supports in case you are printing with supports everywhere.

very easy to do
Very strong
Very durable
No additional tools required


need to insert the Nut at the right time

Step 5: Questions and Comments

As this is my first tutorial , you are welcome to leave any comment for improvement or ask questions .



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    7 Discussions

    Zaphod Beetlebrox

    2 years ago

    Would have been nice to have some sort of a pull out force for each of the methods. Maybe a straight out pull, and a 90° pull. See which is empirically the strongest.

    2 replies
    nqtronixZaphod Beetlebrox

    Reply 2 years ago

    I second this. I don't own a 3D printer yet, but this was the information I was hoping for in this instructable.

    KuuranDIY Hacks and How Tos

    Reply 2 years ago

    One design I tried was to add a solid layer immediately on top of a trapped nut. Slic3r allows you to use support for all but bridges, so it will not fill the cavity of the nut. Make that solid layer only 2 layers deep and it is very easy to remove with a drill bit.