I was having some issues with the lead nut carriers splitting when I bolted them down, so I decided to try cutting these parts from the Trex composite decking. The piece I bought was 1.125in thick, 5.5 in wide, and 8ft long for about $18, I cut it with the same 2 flute end mill I have been using with MDF, and I think they came out well.
Given that the part is now wider and contains a mix of saw dust and plastic, I am pretty sure I will not have the splitting issues.
Another issue I had was that after drilling thru the lead screws and attaching my DIY couplings, I was unhappy with the results. All of them had some amount of wobble, which I found unacceptable, so I decided I might want to just buy some. After doing some searching I came across this site: surplussales.com, which had some 1/4″ to 1/2″ solid brass couplings for $9 each, they looked adequate so I ordered a set of 4 ($41 shipped). They arrived quickly, and I finally got around to hooking then up yesterday, much better. I was so inspired, I went ahead and hooked up all the motors to the lead screws tonight, but resisted the urge to finish hooking up the electronics in favor of getting some sleep (my work will appreciate this I am sure).
I will probably get to the electronics tomorrow, defiantly by the weekend. After that it is just a matter of cutting out the router mount… almost there.