How to solve / fix (seemingly) unfitting 3D part / nut / screw combination

Dear all,
I am about to finish my first MPCNC Primo but are currently stopped with an issue with the 3D-parts of the z-Axis.
I bought my 3D parts at “3D Druckservice-Allgäu” (Germany) and they send me the 3 parts which you can see in the attached pic (Makita machine holder ). As indicated in the pic, the nut traps are designed for M5, however all the relevant screws are for M4 only. In my understanding this is a print/design error and requires the replacement to have either a complete M4 or M5 based set.
However, unfortunately “3D Druckservice-Allgäu” blames it on my incompetence while not providing the actual solution…
Am I really missing something? Or are they just trying to evade additional costs? The only solution which I currently see is to use a 2 component adhesive to fix the M4 in the M5 nut traps (super glue didn’t work).

Many thanks for your reply and help, I am really confused atm.

This afternoon i was building at my primo again, i put M5 locknuts in the nut-traps. It was a bit of a push though. I had to use pliers to push the nut down. It fits well. I printed everything myself.

Dear Kokie,

thanks for the reply. However I am not talking about the M5 nuts being difficult pushing into the nut traps, but that the screw holes are only for M4 screws <> M5 nuts.
Can you use M5 screws?

take a 5mm drill; 3-d printed holes are mostly undersized

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Haha, already thought of that.
However not possible:
a. The wall thickness along the screw canal of the machine holder (part in the top) is too thin and will destroy the fixture
a. Regarding the plate (part in the bottom left, the screw head) will block the proper mounting of the machine holder (part in the top).

Any other takers? I guess I got screwed by 3D Druckservice-Allgäu…

Just to avoid misunderstandings, here is slightly updated pic

If the holes are that much undersized…

You may be able to use a soldering iron, if you have a steady hand. Heat the soldering iron to about the same temperature as an extruder, maybe a little cooler, and press the tip through the hole. Gently pessit around the edges until the plastic softens and the hole enlarges. 4mm should be large enough to get the tip of a soldering iron into it.

If those are V1 parts though, those holes ought to have been correct in the .STL file. They CAN come out a little tight sometimes depending on the 3D printer/slicer, but they should be large enough.

Very standard 3D printer settings, 2 walls should be about 0.8mm thick. If those holes are 4mm (Did you measure, or was it just that 4mm screws fit through?) then you should still have enough wall to get a 5mm drill bit through.You can use a 5mm bolt by cutting a small triangular slot into the tip of the screw with a file or a dremel, so that it will cut its own thread. Look at “self tapping screws” for the general shape of that cut.

Hi Dan,
thanks a lot for your very helpful reply. And sorry for the late response myself.

After all that annoying struggle and esp. disappointing and rude replies from the company selling the 3D parts (why are those guys allowed to sell them??) I lost the excitement in the project… (I had the idea to make a birthday present for my niece, which was 4 w ago, lol)

The holes are indeed 4,2x mm, measured with a gauge. Enlarging the 4mm to 5 mm may work for the machine holder, but for the mounting plate I can definitely only use M4 screws, as the M5 screw head will then again block the proper mounting with the machine holder.

Probably will try 2-component glue to fix the M4 nuts in the M5 nut traps or just burn the whole thing.

Anyways, again taking your time to help, Dan and Kokie_nl

@vicious1 did you see this one?

@blahnik I’m sorry you’re having trouble. I believe all these screws should be M5. I haven’t double checked, but I don’t remember M4. Maybe the M5 screw heads you have are not the same as the parts were designed for? Ryan will be able to say for sure. He know this better than anyone.

I can’t speak for the Customer service of the Germany resellers. But this is the first I’ve heard of trouble.

The parts should be identical as the ones sold at V1 engineering. At least the original models are the same.

Hold on.
Those are Burly parts!
Primo has 2 independent tool mounts
Are you sure you order the Primo parts?


#6-32 screws have a 5/16" nut. 5/16" is the same as 8mm (M5 nuts) or so close that we treat it as interchangeable, but a #6 screw is just a bit over 4mm in diameter.

That makes some sense…

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Well, I need too send an email. That tool holder with the small holes was not designed by me, and is not for the Primo version. So there is a lot of bad things happening here.

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This is a mistake on my part! Errare humanum est.
I messed up something in the order, but the replacement part is already packed and will be dispatched tomorrow morning.


Thanks for clearing that up!