Using the Z axis drive pulley as the motor coupling

Another question for today - with Ian's cast parts kit, one of the Z axis pulleys had a pair of tapped set screw holes, and different sized holes in either end - 8mm and 1/4". So I used it as the motor coupling, giving me a bit more vertical work space in the process. But, my home made three mm (sorry, three key is broken) grub screws are not so great, and I'm wondering if this setup will hold together under the side loading from the Z axis belt.

Anyone else use this setup successfully?

And, what did you guys use for Z pulley rims? I didn't have anything in my kit, going to try it without to see if the belt stays on. Heh.

Thanks again!

To answer my own question, Ian gave me some info yesterday -
Yes, the Z axis drive pulley is used as the coupling, and the pulleys are installed in alternating directions so you don't need extra pulley rims. Nice!

Continuing this conversation with myself in the hopes that someone else might find it useful, I'm now back to looking for a suitable coupling for the 1/4" Z motor drive shaft to the 8mm threaded Z drive rod. Using the cast pulley as a coupler is not working well, I've had it come loose twice already just during Z axis testing, and I think my Z axis is relatively smooth.

My next plan is to find a proper 1/4" ID set screw coupling, and bore and tap out one end for 8mm rod, or machine (drill and file in my case) down the idler rod to fit.

I ended up making a coupling out of a threaded rod coupling and a couple set screws: [forums.reprap.org]

I *think* I used a 5/16" coupling. Might've been 1/4".

Hi Wade, Have you put flats on the motor shaft and the 8mm rod? this greatly helps to prevent slippage.

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Ian
[www.bitsfrombytes.com]

Yes, I filed flats on the 8mm rods, and the Kelling motors already have flats on them. I also put some super glue in there, but I haven't yet tested that just yet, I've been busy working on my extruder.

Just in case, I built a coupler out of a thick 1/4" threaded coupler like Steve's; I drilled and tapped one end to an 8mm thread, and drilled the other side to 1/4" and put a 5 mm grub screw in. I'm having trouble getting enough torque out of the 3mm grub screws, as I don't have proper grub screws and am making my own as needed by cutting and slotting 3mm cap screws. They don't seem to have the same bite as the 5mm grub screws, probably due to the lack of a cupped end. The slots are strong enough though; I've already managed to strip out the plastic threads on one pulley.

It's a bit of work to reposition all the pulleys, so I'm keeping the coupler handy until the Z pulley comes apart again. I'll let you know how it goes.

Overall, I've been amazed at how well everything has worked out - this thing really came together quickly. Just waiting for a few parts that I missed while ordering, and some plastic to feed my extruder.

Wade