I'd make the adjustment blocks out of plastic like Delrin.
Acetal 3 " 3 00 x 6 inches Long Rod Bar Stock White Delrin | eBay Just cut off a slice and drill and tap. You might be able to find a similar size square piece, but I only spent a few seconds searching.
Yes, you would be better off with dowel nuts. You need to be really careful if using wood screws, as MDF splits incredibly easy when screwing into the edge.- The plans call for 1/4x20 screws for connecting MDF to MDF with no bolting (e.g., connecting Z axis platform to Z axis bearing support). That doesn't make sense to me. Seems I'd be better off with either wood screws or machine screws with cross-dowels / barrel nuts.
The 1/4-20 is just what was popular 10 years ago. If someone had thought of using dowel nuts back then, that's probably what would have been used.
A lot of innovation occurred after the JGRO. Today, there are better ways of doing just about everything.
My galvanized pipes have the coatings continuously flaking off, even after around 200 hours of use.- Black pipe vs. galvanized steel? I'll probably do black pipe and sand it down.
Sanded black pipe is a better option. If you look through the old Joes 2006 threads, you should be able to find some home brew methods of making a lathe type sanding jig.
I made a tap for my 1/2-10 Z axis. Then I broke down and bought dumpster nuts for my X and Y axis. I used a dremel to cut/grind 1 or 2 slots, then a stationary disk sander or grinder to put a taper on it.- Lead screw and tap. I'll probably get Acme 1/2"x10, single start. It appears to be the least pricey of the bunch. But to tap the holes, I'm not as sure what to do. It'd be great if this group could start some kind of tool lending program. I'm intrigued by those who have made their own taps, and might take a shot at doing that. But I have zero metal milling skills.
Google "Making Acetal leadscrew nuts the easy way" to see a method that doesn't require a tap.
There's no vertical force on the Z axis pipes, so they don't need much support. The leadscrew carries all the weight.- The pipes that are connected through the X axis top and bottom plates, and thus allow travel of the Z axis bearings, appear to go through the holes and therefore they're not really supported from below. They're only held in place by the adjustment blocks. That seems, well, unsupported.
The gas pipe on the longer axis are the weak link ion the JGRO. Making aluminum parts won't help much, and may make things worse if they add additional weight.- Shouldn't I just bite the bullet and make it out of extruded aluminum? Well, I got this far and like the woodworking aspect...
And if this is mainly a learning exercise, don't spend any more than you need to.