SO3: Milling wasteboard flat shows stair stepping

In order to make surface that is truly flat to my SO3, I created a rectangle in CarbideCreate with a 0.15" deep pocket fill using Carbide’s tool #201 (1/4" flat end mill) in hardwood and just used the default speeds. (The DW611’s lowest speed is much faster than the 9000 rpm Carbide Create suggests, so I just used the lowest speed on the router, which I think is 16,000 rpm). The resulting surface seems less flat that what I started with, with router indents at all the corners and in a few other places. Is this just because the Z-plate is not completely rigid or likely something else?

Thanks for any thoughts!

Please check out the squareness of your machine, esp. the spindle:

Also, some fine-tuning may be needed:

Thanks, Will. I watched the video and read the post about squaring the spindle, but I’m sadly not sure which action to take next. (I’m very new to CNC and machining. I don’t have a machinist square other than a Starrett 6" combo from woodworking, but am happy to order things.)

If I understand the links correctly, I first need to make sure the wasteboard is square to the Y-axis aluminum extrusions. If its not, are there screws that I can adjust to make it more so? Or would using the aluminum wasteboard solve that problem? As for squaring the spindle, I’m also not clear what adjustments can be made once I use one of those dials or calipers to see if it is sitting square. Sorry if I’m being slow, but when I square the guard fence on a belt sander, for example, there are two screws that I can loosen and then move the fence and then re-tighten in the square position. But to make the DW611 more square, am I loosening and tweaking the spindle mount? Won’t it just go back to the same position when I re-tighten it to the iron Z-plate? (Again, sorry if these are dumb questions.)

To make the DWP spindle mount square you should be able to loosen it, adjust it to vertical, then re-tighten, there ought to be some circular play.

To adjust along the other axis either shim the V-wheel connections w/ foil or loosen the screws on the X-axis extrusion, twist it to make things perpendicular then re-tighten

The square you have should be fine to start w/. Just be patient and check one part against another and continue adjusting until you’re satisfied. You may have to do things repetitively, chasing yourself into smaller adjustments.

Just be patient. Might need to drill out some holes though, see twforeman’s blog post.

Thanks, Will. I checked the spindle mount and it turned out to be perfectly square to the wasteboard, although I then installed the new Z-plate that Edward sent me and updated my version of Carbide Create and Carbide Motion. I did the same basic test using the other side of that piece of oak and the results are much smoother, even though the new cutting defaults are faster and deeper. As you can see, its still possible to see the lines where the 1/4" bit traced the pocket pattern, but the board feels pretty smooth to the touch.