I started by buying a non-ferrous metal blade for my table saw / mitter saw, this blade is expensive but worth it
After making sure my saw was straight, I proceeded to cut both Y axis extrusions using a stopper on the saw to ensure both side will have the exact same length, I sprayed a bit of WD-40 for lubrication.
I then proceeded to tap the ends of the extrusions with 1/4-20 tap. My tap wasn’t long enough to tap all the way so I resorted to a 5/16 hole 1/4″ deep following with tapping. I used 3-in-1 oil for lubrication and cleaned up with compressed air.
I then cut the linear rail to 1425mm using a grinder (the rail is case-hardened and cannot be sawed).