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Drop-in t-slot nuts

by whosawhatsis, published

Drop-in t-slot nuts by whosawhatsis Mar 24, 2012
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Drop-in t-slot nuts by whosawhatsis is licensed under the GNU - GPL license.

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These will accept an M3 nut and then drop into the slot in a 20mm profile t-slot aluminum extrusion (incl. MakerSlide). No need to slide in and out from the ends of the extrusion! Insert a screw and turn clockwise to tighten and it will turn 60° to lock in place. Turn counterclockwise to loosen and it slips right out of the slot. I have only tested it with 20mm and 25mm profiles, but it's parametric, and should work with any profile larger than 20mm. If you find settings that work well for other profiles, let me know and I'll update the files.


These are tiny, and the first few iterations didn't work because there was too little material to reliably produce the shape. You'll want to print a lot of them at once for cooling purposes, and the scad file has variables for duplicating it along the X and Y axes.

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Are these supposed to break when you insert the nut? Mine are so tight that some of the corner plastic breaks off when inserting the nut, since the walls are so thin. I printed at 50% infill.

No, they shouldn't break. Sounds like your printer/slicer might need some calibration. Either that or you have unusual nuts. If you use the OpenSCAD file, you can adjust the size of the nuts to make them fit better, but considering that I printed these on a CupcakeCNC, if your printer can't make them properly, it probably needs some work.

Are both the 20 and 25 mm versions for M3 nuts? I wanted to use M5 and may try to scale it, but thought I would ask. I think M3 may be strong enough for my purpose if I had to. Thanks for the design.

These need to have a regular metal hex nut inserted into them. 20/25mm extrusions have 6mm wide slots, which will not fit a nut larger than M3. There are larger extrusions that I believe have an 8mm wide slot, which would fit a nut up to M4, but you're obviously not going to be able to drop-in a normal hex nut for the screw size that the slots are intended to work with, though you can buy special metal nuts that are a similar shape to these (and are much more expensive than hex nuts, which is why I designed this).

Ok, Appreciate the info and insight.

Worked perfectly for my Kossel thank you.

could upload just a single nut? I found the spacing on these 6 a little too close for good cooling on my printer. I had to reverse-engineer the .stl so I could get better spacing and multiple copies w/ slic3r. other than that, awesome - thank you!

Yay ! It was on my to-do list, glad someone made a printable M3-t-nut ! The metal ones are damn expensive otherwise...

Nice design!

Is it easy to modifie it for 4mm nut?

Assuming you have an extrusion with slots large enough, dead simple. The slots in my extrusions are too small for M4 nuts.

You would need to forget about the "drop in" part to make some for M4 when the channel is only 6mm (standard M4 nut is around 6.8 mm).

Maybe try to print the whole thing in plastic and tape it ? Will not be as strong as metal nuts for sure.