This is just a curiosity question. I see that a lot of OpenBuilds designs use 8mm 4 start lead screws. Why not 3/8" x 4 start? From what I have found they are much cheaper. The increased size too large for clearance? Just asking.
The 3/8 are cheaper. But, the associated parts needed (anti-backlash nuts, bearings, flexible shaft couplers) cost more. I am using 1/2 inch 5 start and 3/8 inch 4 start in my build, but I am doing it the hard way by using bits of the rods to make my own taps and I bought a Delrin block from McMaster Carr. If I fail I am out the $18 for the Delrin but I had fun trying. If I succeed, I save money on the nuts (about $60) and I had fun trying. To lower my costs, I am machining the ends of my 1/2 inch screws to 12 mm and my 3/8 to 8 mm so couplers and bearings will be way cheaper. Both rods move 1/2 inch per revolution. If you want to save time and come out about the same, the 8 mm screws make life easy. I am building longer than 8 mm can handle, though.
Also, unless you make your own nuts like I am trying to do, the anti-backlash nuts that I have seen for sale will not fit in the C-beam without modifying the gantry plates.
As far as price goes, Dumpster CNC has some pretty good prices on anti-backlash nuts and other fittings for the imperial sized ACME rods. But again, getting them to fit the Openbuilds system is another story.
I will probably get mine from Dumpster CNC if I fail miserably at making my taps. I had also considered HDPE and molding them. But I figured the Delrin was a little bit better.
@Giarc Devestator over on CNCZone has done what you're trying, might have some in-site on creating the taps. Let me know how your attempt turns out. I have some left over 3/8" 4 start pieces and might try it myself. @Rick 2.0 I'm currently using DumpsterCNC anti-backlash, collars and couplers. Happy with them, so far. I asked because I am planning on building another machine using v-slot C-beam components and I'm gathering info.
