Bit breaking in the collet - Cause?

Hey guys, so I’ve been using my X-Carve daily since I got it about a month ago and it’s been going very smoothly after overcoming a few challenges early on.

Today, I’ve run into an issue that I can’t seem to get an understanding of, and hoping others with more experience can provide some pointers.

I’m carving a sign, using a 1/8 straight bit on 3/4" Birch, carving at 120 in/min. I’ve carved this same exact sign several times already and have had no issue, with the same settings. About 25% into the rough pass I noticed that my bit broke inside the collet I removed it and inspected the collet and it seemed fine. I assumed it was a fluke of some sort and I replaced it with another, a brand new bit. A little bit into the carve, the same thing happened.

Both bits shattered inside the collet at the exact same location.

I put in the 3rd bit, and what I notice is that in certain areas, it gets bumpy. I’ve turned the feed rate down to a very low rate of 20 in/minute and so far it hasn’t broken, but it also doesn’t look right. When it’s carving the wood in certain areas it looks bumpy, while in other areas it looks smooth. I’ll attach a picture of the carve below, showing what I’m talking about.

Could it be just stubborn wood?

If the bit is breaking inside the collett its not secured/tightened enough or incorrectly.
Can you show us a picture of the broken bit, collett/nut and how the 3rd bit is inserted?

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I’d say slow your feed down. 120 IPM is pretty fast in a dense wood. This said" irregular grain may be difficult to machine and may be prone to tear out" I’m not sure whether that qualifies as irregular or not but…

Which collet adapter are you using.

One thing to check. Remove the collet and nut. Examine the threaded section of the spindle, on the router. I had the problem, that this actually cracked. Some speculation, was that the 1/8” adapter, for the stock collet, may have caused it to crack.

I have a similar issue, DeWalt with precision collet and 1/8inch straight flute bit. When I use the “black” 1/8 inch straight cut bit in the precision collet they started breaking. Only those bits, always at the same distance. I changed the collets already, did not help. Inside the collets appear a little “rough” about the height where the bits broke. Filing the inside “clear” with round file did not help. I think the lenghts of the bits they can be stuck into the collet is rather short, due to the black collar. I decided to buy same kind of bits, w/o collar, longer shaft lengths, and ordered new collets.

I think the length of the bit that can be used to fix it in the collet is of importance. Will see. If I am wrong I report back. I recommend inventables to re-design their 1/8 inch straight bits, otherwise they are excellent (different collet).