NOT big or deep wood Martin....and not really cost effective for most....but thought I'd mention.
When first doing round buttons(.2-.22" thick on 4 species)...we were after production times and just prototyping and only looking at machine times.
On 2015 before we swapped to HDO and a 2 tape method....the protos made sense even with "Bad" spots at 45 degrees to the grain on the cutout.
There really weren't THAT many protos to sand, and slight differences in diameter didn't seem a big deal.
THEN we started selling and I trained up my Dad's old secretary(who had to quit office work because of a stroke) to finish buttons,and found the Bad spots on 2 species took 5 times the amount to sand, AND weren't always uniformly round!
Had a 20% reject rate, as Dad would not sell "Seconds".
I WAS cutting in 4 passes with a final pass of .01"
Played for a few days 3months after first pic, and found 9! spiral passes, with a final pass of .001" had NO bad spots 99%+ of the time.
We went from 2-5 minutes sanding on the Foredom with a detuned flap wheel......to an average of 30 seconds per button
NOT practical for most to do a "Finish" pass depth on thick stock, but when I'm doing One-ofs...I always pick a sharp bit and remember that.
NOT sure it would have made any difference on that piece....but if an extra 4-8 minutes on the machine would have saved that sanding?
I looked for better close up pics, but couldn't find any:( Zoom pic and you should be able to see the difference