M4 screws and problems with nut traps (Europe)

Ryan, would it be possible to add a hint to the part list/assembly instructions, that M4 screws are also usable as an alternative to the M3.5 screws? I spent two days on sourcing M3.5 screws, without success. They are very uncommon in central Europe (at least in German speaking country’s). No local store is offering them, and only a few special online shops are able to ship them.

I found the hint on using M4 screws as an alternative in this forum. It would be great to have it in the official instructions!

The M4 screws worked well for me, but the related nyloc nuts are massively causing difficulties to me. I think there are completely different nut sizes in Europe (or maybe in every single country?). The nyloc nuts available for me are measuring 7mm flat to flat. All the parts of the MPCNC have nut traps measuring something about 8mm flat to flat. All nuts are spinning. I had to fix the nuts with pincers while screwing. Not easy with some parts, but possible with one exception: the tool mount!

I do not have a really good idea how to stop the nuts spinning in the deep nut traps at the back of the tool mount. At the moment I try to print “nut enlargers”, with moderate success.

Maybe I missed some info? For sure I am not the only one with this issue.

Please give me a hint.

Thank you!

That is the problem, they are all different flat to flat for some reason from country to country on the M4. So while they do work, they kind of don’t at the same time, so I can’t really suggest people use them. I have done my best to make this easily sourced through the entire world, those of you who can’t get M3.5 at the local store have it the worst but I’m sure you understand why it has to be made to fit the largest nuts. easier to fill a whole than dig a new one in plastic.

Some people have made adapters/spacers to help with the tool mount.

The only thing I can suggest is getting M3.5 or better yet some 6/32" online to really make things easy. With two size options available one has to be able to be sourced. 6/32" is the most common machine screw in the US so they should be easiest to source in my opinion.

I wish it was easier but I do not see any other way around it, this is the least specialized way I could find to do this. A globally sourced machine is extremely difficult. If I didn’t worry about making it compatible I could very easily make a new center assembly with smaller bolts and bearings, but then you would be forced to buy my kit.

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Ryan, thanks a lot for your very quick reply.

Have not known, that M4 nyloc nuts are that much inhomogeneous around the word. Strange thing. I know that you did your best on making it available to the entire world and I am very thankful. It is a big thing to design a great machine and make it open source, and it is unique to have in addition all the world in mind! Thank you very much!

It is absolutely clear to me that it has to fit the largest nuts. Filling a hole is definitely easier. That is, what I have done now with self made adapter/spacer.

At first I thought to order some 6/32". But then I noticed the price of inch-screws in Germany/Austria… I quickly got back to my work on the “nut enlargers”. (60 piece of 6/32" screws with related nyloc nuts ~ $45 – in comparison 60 pieces M4 screws + nyloc nuts $3.5)

This gave me some new motivation. Now the holes are filled properly and the tool mount is working with my small M4 nuts :slight_smile: .

The killer would be a customizable design :wink: (openSCAD files with changeable variables for example :slight_smile: )

What you can do is to simply epoxy the nut in your nut trap, so that it doesn’t spin anymore.
An alternative it to simply heat the nut with a lighter and press it into the nut trap. It will melt the plastic under and go a bit deeper, thus securing the nut in place.

In my opinion, it is harder to fill a void than to enlage it. Would probably be better to make the nut hole smaller, because you can very easily widen it using the heating technique.

I sourced mine from http://www.modelfixings.co.uk/nuts.htm#metric%20nyloc%20nuts