I currently have a converted BF20 CNC mill, and I have been toying with the idea of building a CNC machine using linear rails rather than ways for all 3 axis, and using the BF20 head, or at least the spindle.

I started out by using the base, saddle and column from the BF20, modeling everything out, removing way material to place the linear rails. I have seen some similar threads in the past. But than I started thinking, if I am going to build this thing, I probably want it to be bigger and beefier than the BF20, and would rather kind of custom build the whole thing.

My question is, could I build a new base, saddle, and column out of aluminum, or would it have to be made from cast iron or some type of steel? My thought was to use very big, beefy solid blocks of alu for everything, and just remove what is needed. I even thought about making a larger head out of alu as well, boring out the hole for the spindle.

I would still use the BF20 table, as I have no desire to rebuild one of those.

Ultimately, the main use would be for cutting aluminum, and occasionally cutting steel or cast iron. I really want speed, and I feel the ways are just such a maintenance PITA.

I suspect the biggest issues would be rigidity, as well as a lack of scraped surfaces, but the mating surfaces on the BF20 sucked anyway, and needed a lot of shimming to tram the mill in. I also know alu is lighter than iron, but the BF20 has tons of gaps in the cast iron and space, where the alu would be all solid.

Would this work? I can't imagine a whole lot of deflection. Would love to hear any thoughts on this.