Tramming

[BlueFin]

Ok, so I finally put an indicator in the spindle and my results are: From the center of the spindle to a radius distance of 4" out I get a difference of .003" in elevation from right to left along the X axis and a difference of .001" from front to back along the Y axis. My X axis is obvious, as looking at the machine the right side is .003" low and the left is at 0. My stand is on wheels and is also a bit more flimsy than I thought it would acutally be. So I threw a paper cloth on the floor that was folded in half and then rolled the right front wheel up on to it. This immediatly cut the difference of tram in half to .0015". And that would make sense. I am going to make screw down feet for all 4 corners so I can level the machine and get the X tram perfect.

But how can I adjust the Y tram without taking the machine apart? I guess I could live with .001" over 8" when using a 1/4" end mill, but you can really notice it when using a 2" 1/2" fly cutter.

[philbur]

0.001" per 8" is within spec. If you want to fiddle some more then you need to check if it's the column or the spindle, it's probably a bit of both. You can possibly adjust the spindle, if it's leaning forward (which is the most likely), by adjusting (tightening) the Z axis gib. A slight lean forward is possibly a good thing anyway as it will tend to be corrected when the machine is under load.

Just some thoughts and opinions.
Phil

But how can I adjust the Y tram without taking the machine apart? I guess I could live with .001" over 8" when using a 1/4" end mill, but you can really notice it when using a 2" 1/2" fly cutter.

[keen]

Hi - It surprises me how much the stand affects the machine accuracy. What it means is that if the base of the machine is twisted in at least some directions - (by being bolted on a stand that does not match the bottom surface of the machine base). Then the flex is transfered into the main machine castings and causes quite significant displacement.

I did not think it would flex that much - we live and learn. I have my machine on a welded steel frame that is quite solid. I thought I was being overly cautious when I fitted a heavy thick (3/4") ply 'insulater' between the stand and the base of the machine. I also only lightly nipped up the mounting bolts - my theory was that the ply would 'give' where needed - so any mismatch with the stand would not be transfered into the machine castings. This seems to work as the trammeling produced remarkably accurate results. I have never had a mill that is square and parallel to within one thou over 12 inches in all directions before. Now I wonder if that was a fluke - and if I wheeled my machine to a different position, if it would still be as good!