New 1/8" cutting bit causing serious overheating problem

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.
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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.

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

Think maybe the rpm's for the tool has changed? Don't know how to check the speed with out using a tack or a special instrument for rpms. Looks like it cut ok at first but then loaded up or something. Keep us posted on what you find out. Thanks

That looks bad. Glad there was no major fire trouble.

Glad you are all right... scary indeed

Was there any damage to your machine?

Lawrence

No damage to my machine, but my dust pickup which is half wood was charred.

I just finished a rerun of the project with my old bit with no incident (top left). Still using Designer 2 software and firmware. Don't know about the RPMs. Comparing the two results, the new bit does seem to load up the cut more, but it's not a dramatic difference. It is clearly running hotter. I wonder if I could get temperature readings with my non-contact thermometer? Not anxious to use that new bit again though.

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I have to conclude it is the bit. I would like to know the reason for the bit change. I would also like to know how I can get replacements identical to my old one before it gets completely dulled or broken. As it stands, the new style are no good for this.

Any chance the bit and/or holder are not 100% straight?

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Originally Posted by brdad

Any chance the bit and/or holder are not 100% straight?

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Two different new bits, same results.

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Originally Posted by DickB

Two different new bits, same results.

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Do you think the bits are damaged/prematurely dulled now from excessive heat?

Lawrence

Don't know. They definitely got blackened, but feel sharp as I rub my thumb over them. I may get brave tomorrow and try to get temperature readings.

I would like to hear from the Carvewright staff to find out if they changed suppliers. Like most manufacturers, I would assume they are always on the lookout for suppliers who will provide them with parts and bits at a lower cost. They supply the specs and then the suppliers bid on the RFPs. Could be a new supplier. I am sure LHR will do their very best to get to the bottom of this for us. And they cant begin to check things out until they know there could be a problem. Hope this gets resolved for you very soon.