I am building a 4x8 CNC router. My gantry beam is a 65 inch length of 3x4x.125 steel tube. I am using the CNCrouterparts linear rail so I have bolted and epoxied a length of 4x.250 CRS plate to the 3 inch wide side which is the vertical axis. I am beginning to think that this tube, even with the .250 CRS plate glued to one side may not resist twisting as well as I had hoped.
I am hoping to put a 2.2kw spindle on it.
So I have two questions.
Is this beam strong enough?
If not, would welding a length of 2.5x2.5x.375 steel angle across the rear vertical surface fix the issue?
See attachment.
ThanksClick image for larger version.  Name: gantry.jpg  Views: 1  Size: 25.4 KB  ID: 407676