jasoneule,
Thanks for your advice, I switched to using a jigsaw, saved lots of time and effort!
Hearing that tapping with good taps takes under a minute is surprising. On my long list of American tools to buy, taps are definitely near the top of that list.
Anyways, update. I have been very very busy with school(learning calc 1 in a week) and haven't had much time for my machine. But I did get the x-axis moving!
My biggest problem was friction, which was caused by a number of things. When attaching the bushing and backlash nut, I used microcarve's jig to keep the slides parallel to each other when gluing. I took 2 equal sized pieces of wood, cutting notches in them simultaneously, the resting my slides and shafts in them so that they were parallel to each other. Epoxy holds them securely.
If you are still curious in this, check out this thread in which I struggle to understand keep the slides parallel: http://www.cnczone.com/forums/diy-cn...lash_nuts.html
So, after 2 attempts, I got my rails within 1/16" of parallelness. That's as good as I am gonna get, good enough for my machine. The problem is my oilite bushings are too precise, there isn't any play in them and they give me no tolerance. It was difficult to adjust and keep the rails aligned with each other on my machine. Static friction was exisive. I had thermoplastic bushings with .1" of play, but returned them because I thought they were to imprecise. WHY GOD WHY DID I RETURN THOSE? That .1" of play is the kind of tolerance I need on my sloppy little machine.
Here is what I did, leave 2 oilite bushings on one slide, remove the 2 from the other slide. Replace those oilites with a centered, single, 1" delrin bushing. I made this bushing and gave it ~.1" of horizontal play. If I still had those thermoplastic bushings, I would have used them on one side. Smack it back together, and it moves like it's on ice!
I add the threaded rod and introduce waaayyy too much friction (as the voices of CNCzone members tell me I should have bought ACME thread). Well, I cut my backlash nut from 2 1/2" of thread to 1". Also, I filed down the threadless delrin bushing that was contacting the threads too much. Once again, smack it back together and I'm golden!
My motor lined up well, but one of my spacers was too short. Notice in the picture, I didn't screw it in because it pulled the motor out of axial-alignment with the threaded rod. I might add a washer and then add the screw, but for the time being the motor is secure enough. Note the spacers are not curved, my camera distorts close up pictures.
Also, the little thrust bearings work well for $3 each, but bigger thrust bearings would be nicer, I could put more pressure on them.
For my coupler, it fits very well, i left a 1/4" inside the coupler for the flexing shafts, giving lots of flexibility to the system. I am satisfied with the flexibilty and layout. I don't think it will break on me and it doesn't add backlash(that I can measure).
What I learned/What I wish someone on CNCzone would have mentioned:
-Keep your rails parallel if you follow this microcarve-like setup.
-Buy bigger thrust bearings if you can afford them and want to put more pressure on them, I can't tighten against them too much. (Awesome idea from spalm: http://www.cnczone.com/forums/open_s...tml#post102831)
-Buy ACME rods! Good grief, buy ACME rods if it is the last thing you can afford! You can go from 20-20% thread-to-nut efficiency to 60-70% efficiency by switching from threaded to ACME. (I have a source for that somewhere)
-I like my flexible coupler, I wouldn't recommend a similar setup with a soild coupler. Unless of course, you are a master craftsman, then you could probably get away with a solid coupler.
-For my slides, the ideal setup would have been 2 oilite bushings on one slide, and 2 thermoplastic busing on the other, my homemade delrin slide works, but isn't as ideal.
I easily span at 30rpm with mach3, will do some tuning and see how fast I can move it.
I have finished the base, x-axis, and work table. Next up is the y-axis, z-axis, and router mount. Probably won't finish this machine in a month, probably not in two months. Even when I do have free time, its usually spent applying for scholarships.
Wish me luck!
-John