Sunday, 8 December 2013
here we go a-trammelling
I've spent some time re-tramming my Taig 2019CR mill. So far it remains unconverted to CNC. Well, I never said my time management was anything to be proud of.
It is critically important to get the vertical column ways (Z-axis) dead square to the table surface (X-axis) and, at the same time, get the spindle centreline parallel to the Z-axis travel. All sorts of odd errors creep into one's workpieces if the latter is missed; the most prevalent being a dished surface when flycutting during an X-axis traverse.
Similarly, the Z-axis ways must be square to the table surface (Y-axis) otherwise more unwanted errors creep in. This goal is harder to achieve due to the the Taig's column-to-base design. Suffice to say some shimming can be necessary if adjustment is required. Make sure the mating faces of the column and base are scrupulously clean before assembly.
My column is tipped backwards at ~.001" in 3" slope. Due to workspace constraints, I cannot readily correct this fault. This will manifest itself as a small positional error when moving the spindle downwards over long distances. Since the Z-axis is limited to 6" of travel, this effect should not prove too great an inconvenience. However, it can also generate a ridge in the milled surface (along the X-axis) when surfacing with a large radius cutter. Since inserion of the shim to correct the front-to-back error would disturb the current side-to-side setting (error ~.00025" in 3") , I will forego the adjustment for a short time.
I have read online forums that suggest shimming under the spindle mount dovetail to correct the error. This will address the "ridging" problem, but not the positional error created by Z-axis downfeed.