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

[HankMcSpank]

Bill,

I'm not blessed with a lathe - I used a pillar drill at work, figuring I can't go wrong enlarging the hole & then tapping it - like I say, simple in principle, but when you're new to engineering type stuff (I'm more electronics h/w in background),...well, let's just say I wish I'd paid that little extra & got Lee (who sells the same ones I ultimately bought!) to do the M8 tapping aspect! Thanks for the idea about casting - I had considered it, but then I saw how much casting kits cost & I'm unfeasibly tight...I had some 100mm acrylic & wanted to learn CAD anyway, so that's the path I've cjosen (retrospectively, I wish someone sold these!)

I have no idea what you mean by "compliant coupling twixt motor and screw"

korky, I bought 3 x L050 lovejoy type jaw couplers (made by challenge) - these come with a 6.35mm hole drilled in the middle of each jaw. One side will slide onto your stepper shaft perfectly, but the other side of the jaw needs 'modding' to fit what ever diameter/fit your leadscrew is. Mine is M8 threaded rod...which has a 1.25mm thread, therefore 8mm minus 1.25mm, means the tap hole should be 6.75mm. I therefore drilled it to that specification using a pillar drill & tapped the hole with an M8 tap. You'd think this would be a simple job - it probably is to someone who more of an engineering type...but as it turns out, I reckon my inexperience has resulted in me adding in a degree of 'error' making it untrue, which certainly gets magnified when coupling to some M8 rod that slightly bent too!

I'd also read that such couplers allowed a degree of leeway...the two couplers push together incredibly snug with their insert...I estimate my leadscrew -> motor setup is out of whack by 1mm, but the 'forgiving' jaw couplers didn't forgive! I should say though that I have one of those SK12's holding my M8 leadsrew about 2cm from where the M8 rod couples to the motor, so this is probably why I'm not seeing any 'give' supposedly allowed by the coupler.