Example of the importance of tightening bits well and up cut vs down cut

[elbarsal]

Relevant to various discussions of bits cutting deeper than expected, I was watching this amazing woodworker on YouTube accidentally ruin a very expensive project with his CNC machine (not a LongMill - but completely relevant): https://youtu.be/j34KtFaFyQs?si=Z4PrMqcM_3E6tENU&t=1840

The video is timestamped to the exact moment of his big “oops” - where he had an upcut bit pull itself too deep into his workpiece, ruining an expensive walnut slab, and thus his entire piece.

I have in the past theorized that upcut bits can pull themselves into the work (and I have confirmed it when I have had bits clearly pull themselves out of my collets). This video shows the consequences.

Short version - make sure your bits are always tight, and downcut (if it is suitable) won’t pull itself into your workpiece.

[Spamming_Eddie]

Jikes!

I use upcut a lot for roughing but am conservative on how deep the’ll cut. I have this happened once with a balnose that I believe is an upcut too. I just entered the house to idunno, ask something or whatever, glanced the security feed from the camera above my mill and saw something was off. Cut the power to the garage and found the bit hanging from the collet French kissing my wasteboard. Like, deep.

Luckaly It was not a 15K French kiss. I was happy to have that camera feed and finaly could show the misses why I went trough all the trouble installing it.

Some will say, you must stay at your machine at all time, but I know me and that won’t always happen. Long jobs are long jobs and I won’t pause them when going for a cupper.