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z axis threaded rod not gripped by coupler

Posted: Sat Nov 03, 2012 11:22 am
by cjgaus
I have purchased a batch 4 shapeoko and I am having trouple with my z axis coupler not gripping the threaded rod. Is anyone else having any issues?

Re: z axis threaded rod not gripped by coupler

Posted: Sat Nov 03, 2012 11:55 am
by cjgaus
Also is the coupler suppose to grip onto the threaded rod once tightened or no?

Re: z axis threaded rod not gripped by coupler

Posted: Sat Nov 03, 2012 2:04 pm
by T4b
Can you explain how it is not gripping (yes, it's supposed to, have you looked at the instruction at http://www.shapeoko.com/wiki/index.php/Assembly_step_9)?
I haven't got a clue what the problem could be from what you've written.

Re: z axis threaded rod not gripped by coupler

Posted: Sat Nov 03, 2012 2:13 pm
by rpe
Do you still see a gap in the split where the screw is? If you do keep tightening it. You should be able to close that pretty much up.

Re: z axis threaded rod not gripped by coupler

Posted: Sat Nov 03, 2012 3:25 pm
by jsbannis
A few of the original machines had this problem as well. A bit of electrical or plumbers tape around the top will make it tight.

Re: z axis threaded rod not gripped by coupler

Posted: Sat Nov 03, 2012 4:40 pm
by kf4mot
I had to tighten the snot out of mine. Batch 4 also.
I thought I was going to strip the aluminum coupler but it didn't.

Re: z axis threaded rod not gripped by coupler

Posted: Sat Nov 03, 2012 10:48 pm
by cvoinescu
Some of those couplers have both a screw that narrows a gap, tightening the hole, and a grub screw (or set screw if you prefer). In that case, to keep the rod centered in the coupler, tighten the split screw only half way, and do the rest from the grub screw. If there isn't a grub screw, you have no choice but to tighten the split screw as far as needed; some tape indeed helps. I found adhesive aluminum tape to work very well for this purpose.

Check out, for instance, this eBay listing, where you can see that the coupler has both a split with a screw, and a grub screw. That is the best type.

Re: z axis threaded rod not gripped by coupler

Posted: Sun Nov 04, 2012 12:57 pm
by cjgaus
Sorry guys for the delayed reply I am in Australia. Everything is going great guns. Ignore my above posts. I was being a lil girl and not putting some brute force into it and not keeping the coupler tight enough. All is attached nice and tight now.

Re: z axis threaded rod not gripped by coupler

Posted: Tue Feb 19, 2013 5:44 am
by tdierks
I had a similar problem with my coupler not gripping my threaded rod, and had difficulty getting aluminum tape to work in shimming it. In the end, part of my problem was that the threaded rod wasn't actually far enough up into the coupler to grip; even though the end seemed to be past the coupler's gripping screw, not far enough, apparently.

The trouble was that the length of the shaft of the stepper motor, plus the height of the two nuts that secure the rod above the bearing, didn't leave enough threaded rod protruding for the coupler to grip it. (I couldn't get the rod further into the coupler because it was bumping into the end of the stepper shaft.) I fixed this by putting three washers below the nylon spacers on the stepper bolts, so as to move the stepper a few mm further away from the z mount plate; this cleared enough room for me to be able to move the nuts down and get the threaded rod further into the coupler.

Just in case this helps anyone else.

- Tim

Re: z axis threaded rod not gripped by coupler

Posted: Tue Feb 19, 2013 5:49 pm
by phlamingo
Tim, the other approach to this is to trim a couple of mm off the end of the stepper motor shaft. It may be a superior solution, because shimming the motor introduces the possibility of wobble.

Unless, of course, I am misunderstanding your description of the problem.

It took me a while to work up the nerve to cut the end off the motor shaft.