Where did you buy your threaded rod?(cheapo leadscrew!) - was it straight?

[HankMcSpank]

Wow...I'd forgot about this thread...but a lot of reply activity....thanks chaps!

I realise now that I'd not given enough info in my original post.

I am using stainless steel (A4) rod, along with with homemade delrin nuts (delrin rocks!)

I have a fair degreee of misalignment showing at the motors, that I initially thought was just my M8 rod leadscrew being slightly bent I now think is a combination of that with the following 'errors' too....


1. I support my M8 threaded rod leadscrew at each end, by feeding it through a roller skate bearing & then it's all held held by an SK12 mount (these things rock - get some!)....



....The mount in conjunction with the outer skate bearing surface is a perfect fit , but there's about 0.3mm play between the M8 rod & the skate bearing inner circle which it feeds through (meaning a potential 'slop' factor of 0.6mm). I place a nut either side to tighten the rod onto the bearing inner race...but obviously, it's pretty random as to how 'central' I get the rod when the nuts are tightened. I'm at a bit of a loss how to address this...best I can come up with is perhaps use plumbers PTFE tape to help 'take out' this 0.3mm error allowing me to tighten the nuts & get more central)

2. I reckon my jaw coupler holes are also slightly out of whack. I went & bought jaw couplers with a 6.34mm hole on each jaw...one side was fine as that's the exact diameter of the stepper shaft, but the other side needed the hole enlarging & then tapping to thread it onto the M8 rod leadscrew ...I think this might have introduced a margin of 'untrue-ness' (I though having the 6.34mm pilot hole would make enlarging/tapping this hole easy - uh uh!)

The end result, is that the motors aren't turning smoothly...they bind. The workaround (for now), is to loosen the motor mounting bolts to allow the motor some play to physically move & 'go with the flow' so to speak.

What I learnt from this episode...

1. Don't buy your leadscrew rod online! Make sure you can physically inspect it. Tale a long time while inspecting it.....don't just eyeball it....roll it on a completely flat surface.

3. Have someone with the proper tools/experience to drill/tap your motor jaw coupler!

4. Think of a better way of 'holding' your leadscrew (whilst skate bearings are a great idea, the lack of snug fit in the inner race...however small, will simply cause you great headache!)

For all the negativity, my machine works ok, it's just not something I'd want to show off to everybody!

But, hey, this was my first build...we all make major mistakes with that one eh?

I'm now on to my final bit - of my CNC build trying to design/cut a Dremel tool holder...woah - what a palaver. As a temporary measure, I've clamped mydremel to the Z plane (what a kludge - plastica cicular shapes held against flat smooth surfaces is not a good mix)... the Dremel is an awful shape (it's eliptical further up the body!), so even designing it in CAD was grief. But my goodness, that I've come to cut it, I'm findingthe 'clamped' Dremel moves slightly...*very* annoying - especially if you're nearing the end of the cutting run (& esp since I have such slow feed rates)....why did I ever get involved with CNCs?