Y Axis screws not straight

Curious, are the Y axis lead screws supposed to be straight? Both mine are very wobbly, and I am afraid the constant bouncing as the machine moves forward and backward will wear out the anti-backlash nuts prematurely. When I say “very” wobbly, I mean that when the machine is driving in Y, those screws are VERY out of alignment as far as being straight. It works, but I am astounded at how wobbly they are. Am I being unduly concerned?

I would double check the instruction sheet Y-Axis Gantries page, go almost to the bottom of the page and recheck the install of the Y-axis Lead Screws. Pay close attention to how the nuts and couplers are installed.
Here is the link Y-Axis Gantries - LongMill MK2 CNC
Good luck.


Thanks!!! They are installed properly, the screws are just not straight. If you lay them on a flat surface and roll them, they are way out of straightness…sort of like curvy .

Checked and all is good…if it will upload I have a little video I made, and actually after looking again, it is just the right one that is bad…

OK, it doesn’t allow videos to upload. But, the screw is definitely “bent” along the back, what I would say is the last roughly 8" of the screw. Kinda like watching a corkscrew spinning. And it causes quite a bit of vibration on that side.

And truthfully, the X axis screw is not straight either.

I don’t think that they should be bent. You might want to drop Sienci Labs an note and maybe get a new set of lead screws.


This thing has a 90 day warranty and I’m sure I’ll use it all just trying to get to a point I can cut something.

1 Like

Got an email this morning, the guys are sending me new lead screws…

1 Like

OK, so maybe some advice here? I received new lead screws, and during the communication with Sienci, we learned my Arduino board was bad…so, the new board and screws are installed, the first run with no bit and Z offset up high, the job ran with out a fail. That’s good news. However, I did notice that every time the program starts, the Y axis on the right side starts a little quicker or something, causing there to be an ever so slight twist to the X gantry. Anyone have an idea of what I should look for?