I've upgraded my Sainsmart 4030 to roughly a 4090 (400mm x by 900mm y working area). I'm trying to tram it. I've got a Dewalt 611 as the spindle and I'm using a SST (Stupid Simple Tools) mini-tramming tool. I've got it chucked into the 1/4" collet, and the indicators are set for the 4.5" diameter circle. I didn't have any real issue tramming the X-axis. However the Y-axis direction seems to be out about 0.050" from one side of the circle to the other. I've loosened all the bolts on the gantry c-beam and the base plates, but when I tighten it back down, it seems to be right back where it was. Since the angle it is off is where the top of the Z is closer to me, than the bottom, I suppose I could shim the bottom of the router mount until the angle is corrected. But I don't know if that would be the best way to proceed. I did run the indicator across the length of Y. From the front to the back over about 900mm, it drops about 0.010" by the middle of the bed, then goes up 0.020". That doesn't seem to be nearly enough warpage to account for 0.050" difference over 4 1/2 inches. Any suggestions on what I should do? I don't have a lot of tramming experience. Thanks!
Either shim the mount or try and rotate the entire gantry. Though then you get into "is my Z axis off or is my spindle off?" territory, because they're not the same thing. First tram your Z, then tram your spindle.
The bolt pattern for the gantry is off, and there isn't enough play in the holes to make anywhere near close enough of a change. I may eventually take them off and ream them slightly larger to let me adjust it, but not just yet. I put in 1mm shim spacer/washers on the bottom two bolt holes of the spindle mount and that got me to ±0.005". I'll skim the bed and then try tramming again. I've got some shim stock if I need to tweak the angle just a bit.
