Reply To: Z Nut Holder Tweak



I have some experience with lead screws. Upgraded the z axis in my 3d printer earlier in the year.

Point one to note (and probably the most critical point when talking lead screws) the must be perfectly straight PERFECTLY! The allowable run-out to prevent rapid wear of the brass nut is <0.8mm per 1000mm length (this is for T8R3 trapezoidal lead screw)

Any more than this and the brass nut will eat it’s self in a very small time frame. When any reputable company sells a lead screw they will run it through a special “straightening” machine after any cutting/machining had been done, prior to sending it out.

The design of a trapezoidal lead screw/nut assembly relies on a very small and consistent clearance between the leading edge of the thread and the drive surface of the nut. Even small variations in this will lead to rapid wear and severe inaccuracies.

I learned this the hard way. Bought a cheap setup from eBay. Had is replaced several times because it was never straight. Eventually just bit the bullet and bought a quality expensive set through a local bearing shop, and it was perfect first time.

This is one item I don’t recommend cheaping out on.