So I'm doing a conversion of my First brand BP clone. I'm going to use 1" ballscrews and my own mounts to get it CNC. Basically I'll take off the bearing brackets on the X and Y and use 1 1/2" thick aluminum to make bearing blocks and brackets to hold the steppers. They will have the same holes and bolt directly the the table and cross slide all the original brackets, bearings and dials will not be used. It will have 20mm angular bearings on both sides of each bracket, so 6 in all for x and y. Here is a link to the bearing curteousy of HimyKabibble, http://www.vxb.com/page/bearings/PROD/Kit6933 . For the yoke or bones, the part that holds the nuts, will be custom made by me as I just think it will be easier. I'll make it with 1/2" steel plate and I'll use 2 ball nuts per axis for antibacklash with adjustments. The ballscrews will only be machined 5" on each end, except only one end on the Y, machined down to fit a 20mm bearing and then 1" of that 5" would be threaded for 20mm nut to tighten the bearings (shims if needed) and pulley. Seems like a pretty simple design that should work. I've built cnc machines from scratch before so a retrofit shouldnt' be too complicated. The only reason I mention this is to make sure I'm not missing something.
So the most important question I have is how to I get exact dimentions for the bolt hole pattern on the bearing brackets with relation to the center of the hole for the original screw. I'll be machining the new brackets on a CNC so I need accuracy. Also since this is a clone how would I measure the existing one and get accurate results? I'm pretty good at figuring things out but can't think of a way to chart exactly where the holes lie.
Next question would 1 1/2" thick x 5" high x 15" long aluminum be good enough for a cnc conversion or will there be flex, should I use 1" or 1 1/2" steel? I need it thick enough to make pockets on both sides of the metal for the bearings. Or is there an easier way to mount the bearings I'm missing?
The yoke (bones) will be 1/2" plate and I'll probably make it a little adjustable to make sure I get everything in line properly unless I can figure out a way to make a bracket with the same centers as the original, and again can't figure out how to measure the exisiting hole in relation to their mounting holes.
That's it for now, thanks in advance for the help. I'm really looking forward to have this converted. I'll be posting pics of the progress as I proceed.
I use a CNC Mill like a CMM, indicate one hole, zero the incramental coordinates, indicate the other holes writing down the X,Y coordinates from the first hole and just draw that in CAD and go from there.