Replies

1. 
   chiwoodworker | May 23, 2025 07:40pm | #1

   He doesn't explain much. But, trust me bro.

   In all fairness too many holes in the same vicinity too close together drilled at a rate that is too fast one could start a fire.

   However this feel like clickbait. It almost feels like they could have experimented to achive this on purpose. More! Deeper cut, slower feed rate, closer together! If the bit never raises high enough to eject chips it's rubbing wood against wood. Like the guy on Insta that purposly injured himself to convince his wife he needed a sawstop.

   Yeah, lighter passes, proper feed rate. Let the chips eject. I've "smoked" bits without a cnc by being too agressive.

2. 
   jharveyb | May 24, 2025 09:59am | #2

   The key here is the down shear bit aspect. You are shoving the chips down into the hole and compressing them, with them getting hotter and hotter as the bit spins against them. Feed rate wouldn't change that. Slower router rpms would slow the process, but not prevent it. Down shear bits should only be used where there is some place for the chips to exit.

1. 
   theboom | May 24, 2025 10:10am | #3

   I think your answer is spot on.

   So, it has nothing to do with bit diameter mentioned in the quote?

3. 
   jharveyb | May 24, 2025 03:34pm | #4

   Actually, it might. If you have a large bit diameter, the flutes are larger, and it is more possible for chips to go upward against the downward thrust of the router cutting edge. With 1/8" bit, there is almost no room for chips to go upward. I still don't think downward shear bits in closed situations are a good idea, but they are less bad in larger diameters.

4. 
   Deleted | May 24, 2025 07:20pm | #5

   “[Deleted]”

5. 
   geedubbee | May 24, 2025 11:26pm | #6

   Right. CNC is not plug-and-play like they make it out to be when trying to get you to buy. Bit geometry, feed rate, spoil volume removal. dust collection. blah, blah, blah. Just as with the use of any tool, proper technique yields good results.