Hi routalot, if that qu was aimed at me, no, I have not bothered with toolpaths yet since that is more a case of using a CADCAM package. I need to concentrate on finishing the h/w , without which the rest is a bit academic
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For OP, here is the new format guideblocks. This should be easy enough to make and is way more rigid than messing with bolts and pipes. I does require being able to tap an M10 thread in an ali block. The 45 deg face was cut with a hacksaw and a couple of hours of careful work with a file and an set square, once the holes were drilled and tapped. Conforming to OP's do it by hand objectives.
http://piments.com/cnc/new-guide-block-pair.jpeg
mounted on machine:
http://piments.com/cnc/guideblocks-detail.jpeg
Note scrapyard origin of the ali blocks. They were previously used by someone to mold lead fishing weights, explaining the odd cut-out on the inside faces ! LOL.
I originally started with 80mm I-beams but as the weight of the gantry and z-axis assy crept up to 50kg, I found they flexed too much ( a couple of thou ). Always worth digging out the formulae from somewhere like engineering toolbox before building a rig ( or at least putting a dial gauge on and leaning on it ).