The ballscrews came. We have good news and bad news.
The good news is that the sizes are perfect, the fit between the plates is great. The bad news is they messed up the threaded part.
But we will still make them work.
We have two options. It might take a while, depending on what cure we pick and where the medicine will come from (EU or Far East). Then it’s all downhill.
So, after the guy at the hardware store saw me for the third time in 3 days getting samples of nuts of all M12 pitches (M12x1.00, M12x1.25, M12x1.50, M12x1.75) and still failing, he asked if I wanted to borrow his thread gauge. I said sure!
The pitch is coarser than 0.8 .
The pitch is finer than 1.0 (which was the given spec) .
Yep, 10 threads can fit in 9mm. Holy #$^#, this is 10% off!
Now, here’s the most interesting part. Due to the backlash in metric threading, collision between a 0.9 and 1.0 pitch (i.e. a 0.9 screw and a 1.0 nut) occurs after the 4th thread. If you look closely, you can notice that the first thread touches the right side of the gauge’s tooth and the last thread touches the left side of the respective tooth. The next one will collide.
Which gives us solution #1.
Even though the thinnest standard nut I can find (DIN439) is 6mm thick => 6 threads => collision, some people do make even thinner ones. These are 3mm thick => 3 threads => no collision.
And here’s solution #2.
Forget the nuts. Use a shaft collar.
Solution #1 pro: better fit, can use pairs as jam nuts (or even fill the whole threading all the way up to the coupler as a big nut/spacer => bombproof)
Solution #1 con: slow delivery
Solution #2 pro: fast delivery
Solution #2 con: comes second in fitting tight (axially)
Or I can get both, they are pretty inexpensive, and see what I’m happy with.
And, btw, since I’m gonna have to wait some more, I took the opportunity to also order some 0.1244" dia, grade 25 balls to replace the 0.125" ones that came with the ballnuts. They do fit, but thought to make them a little smoother in order to (a) not overwork the motors trying to beat some extra friction and (b) extend the ballnuts life. More on that when they come.