New 1/8" cutting bit causing serious overheating problem

[DickB]

I've cut dozens of these gears in the past, and never had a problem like this until today. The project board is 1/4" Baltic birch on a 1/2" sled. The cuts are made in one pass. I've run the same project with the same material and sled a dozen times. I did switch to Designer 2, and also used a brand-new bit that I just got from LHR. The new bit is seriously overheating to the point of starting a fire. I had smouldering sawdust in my dust collection system. Scary.


Since I changed both software (machine code) and bits, I compared predicted cut time for the project with both Designer 1 and Designer 2, and they were identical, so I don't think the feed rate has changed. However, comparing the new bit (right) to the old (left), the spiral flutes are tighter on the new bit. I believe sawdust is not being ejected from the cut as well with the new bit. This causes overheating to the point of heavy charring and near fire. This is not a fluke; it happened twice. Like I said, nothing like this has happened before, same project, same wood.



I am making another run with the old bit. Of course I will be keeping a close eye on this.