Wasteboard screw-up, sigh

After building my enclosure and table over the past 3 solid weekends (in the freezing cold) I finally got to wasteboard surfacing. In Easel, I simply created a 32.25" square workpiece with a square centered on top of that, set as a pocket cut. Super simple. Set the bit as a 1" bit, upped the feed rate from stock and set the depth of cut to .0625". Set a ramp-in too.

I zeroed the Z axis manually, just lowering the bit to when it touched the wasteboard surface just barely, then zeroing. XY were in the homing position anyway, zeroed.

The cut was deeper than 1/16" for sure, closer to 1/8th. Just eyeballing it as the cut began, I estimated my counter-sinks on the wasteboard screws would be deep enough. I was wrong. The surfacing bit skimmed every one of those screw heads which was enough to ruin the bit. The wasteboard gets progressively less even the further the bit got down the board. So totally not-surfaced wasteboard and totally ruined bit.

So literally the first thing I tried was a disaster. What did I do wrong with the Z depth?

Was the cut deeper than 1/16 at the point you did your Z zero? Or did it change as you went across the board?

That seems strange.

Maybe the bit slipped in the collet? Wouldn’t expect to see that right at the start though.

Maybe you did something wrong with the Z setting. Perhaps try some test boards and see if it repeats if you go through a fresh homing and zeroing.

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Good point- I didn’t think about that side of the board being at a different level which would make it deeper some places, and not others. Seems like it was consistently too deep. I’ll continue testing and see. In the meantime I’ve ordered a new surfacing bit! This one is smoked!

When I surfaced mine I forget exactly how deep I went, but pretty sure was much less than 1/16. Goal for me was to take off a TINY bit. On the first pass not every part of the spoil board got touched. So I ran it again until the entire board was touched. Then I trammed. Running a surfacing bit is tough on the trim router so small cuts are in order.

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Good to know @KenA . This next time I’m going to zero to the current height and then just do barely anything, maybe a couple thousandths.

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I’ve thought of something else. I’m going to do a spindle and had to learn a lot about EMI issues. I wonder if you might have a noise problem that caused the Z-slider to move too far that one time? Doing some more tests and seeing if the problem repeats consistently would help determine that.