Tension bolts, should they have play in the holes?


Attempt of MPCNC from Spain here! Thanks Vicious! I hope you all understand my poor english.

I’m having problems with movement, especially in Z axis, and I read plenty of times at the forum to loosen o tighten the tension bolts. It is not clear to me if the tension bolts should have play in the holes when they are loose, in the parts that I printed they are tight although I have them loose to the max. I can’t move them by hand.

I suspect my printer do holes smaller than they should and maybe I can’t do a succesful MPCNC.

Luckily plastic is easy to drill… If the bolts are an interference fit, just run a drill through that’s appropriately sized for the bolt. They should move freely through the hole without too much side to side movement.

Thanks, I will have to take apart the thing and try some sanding/drilling :’(

The hole size should not matter, if you have a bolt in there it fits.

Are you 100% sure you used the right sized conduit? What letter parts did you print (c, f, J)? What are you using for rails and what is is measured outside diameter?

The new Z axis doesn’t really have this issue if it is not the above problem. Maybe your nut lock and spacer are out of alignment?

I was just writing a new topic about this thing I just saw:

Wear 1
Wear 2

Bad camera, worst photographer, hope you can see it. The bearings just flatten (flattened?) the tubes.

I’m using 25mm steel tubing, 19mm inner diameter, it’s a kind of precision hydraulic tubing I think (DIN2391 NBK seamless). My machine has no more than 2h of movement, enough to put the right tension to the belts, make 2 drawings and realize that the allthread is not moving ok. The parts I used come with an F.


The wear is normal, steel on steel, one of them has to give.

You need to fix the z axis, the nut lock and spacer are probably out of alignment, or your z assembly is not parallel. run through that section of the assembly instructions again.