X-Carve Breaking Bits


I am having some issues with my XCarve… Its been breaking my bits like crazy…
What could be the cause of it?
I broke the 1/32 inch bit in soft plywood, with a 0.5mm depth per pass and a feed speed of 500 mm.
I broke the 1/16 inch bit in cherry, with a 0.6mm depth per pass and a feed speed of 600 mm.

I am afraid to do any more carving before I can sort this out… I hope someone can shed some light on the matter.

Thank you.

I’m afraid the machine isn’t breaking them… You are. Slow down your speeds by about 100-150mm/min and do a .3mm depth per pass. You are asking the bit to do to much. There are feed and speed calculators if you look it up on Google.

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Ditto. If you do a search of this forum, you’ll see a lot of similar posts. The solution is slowing the feed rate. And, yes, I know this from personal experience, too!

0.3mm depth per pass is a bit slow, don’t you think? Thats twice as much time.
I knew I wasn’t purchasing an industrial cnc but 0.3mm seems slow for pretty much anything, or am I mistaken?

Try 350mm/min and stepover of 40% at 0.5mm and see what you get. Those bits are very fragile. If you used an 1/8" you can push it a bit.

Its not about what the machine is capable of, its about what the bit is capable of.

If you want faster, make sure your design allows for a larger bit. The x-carve can handle it no problem.

Would a better spindle fix the problem aswell? At the moment Im using the 24V DC 300W Spindle.
I don’t plan on ever doing metals, soft and hardwoods only.

Does anyone know of a blog or something where the xcarve doing wood is the main star?


This is purely a bit issue, the thinner the bit, the slower you have to go or you’ll put too much stress into the bit. When I did my CAM course in university the rule of thumb for depth of cut was 1/2 the bit diameter. So when you look at that for a 1/32" bit, a 0.4mm depth of cut is about where you need to be (if not shallower).

As for the speed I’m not really well versed in this topic but it’s pretty clear it’s too fast and putting alot of strain on your bits.

Small bits = loooooooong cut times

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A better spindle wouldn`t change a thing I believe.

As long as your spindle and machine are decently tuned it has power and rigidity enough to handle those small bits. It`s when you try to push the larger bits at faster speeds in harder materials that these things become a problem for the accuracy.

Breaking bits are in general a sign that you`re asking to much from the bit , not from the machine. (again, supposing your machine is tuned.)

Use a larger bit like 1/4" or 1/8" to do the rough cut, and then just use the 1/16 or 1/32 for detail. You also probably want to avoid cutting slots that narrow, as even if you have the feeds right, there is no room to clear the chips once you get to a certain depth.

For 1/16 and 1/31 bits a better spindle LIKELY would not change a thing. However, for 1/8 and 1/4" bits it makes a huge difference. The vibration, loss of torque and run out of that spindle will greatly increase the likelihood of breaking bits. A few things not mentioned above and just based on my amateurish experimentation over the last 10 years of homemade CNC machines:

  1. Bit length. The less bit sticking out of the collet the better - exponentially better! Try cutting your bits down to reduce stickout. (I almost never have a reason to use 1/16" bits - let alone 1/32 for anything other than fine surface detail - I wouldn’t consider profiling with them)

  2. Bit Mass - a 1/4" bit can easily cut 1/4" deep in woods. The same cannot be said for 1/16" bits unless only 1/16" to 1/18" of the bit is emerging from the collet - then it probably would not be a problem.

  3. Torque and Router Mass - Mass = stability. More torque means the bit is more likely to effect the wood, rather than the wood impacting the rotation of the bit. Each time I upgraded the spindle it handled faster and deeper cuts even with small bits.

You can’t go crazy with bits less than 1/8" - they just can’t handle the strain and many are WAY to long to be practical for anything but light scratches - especially in harder woods like cherry, oak, etc.

I had the same problem when I upgraded my Shapeoko2 to the X-Carve. Initially, my Shapeoko2 was upgraded with a dewalt dw660 but it was so noisy that I decided to install the 300W 24V spindle when I upgraded to the X-Carve. Big mistake, I couldn’t get half of the feed rates I had before and most of the time the bits would break. I re-installed my DW660 spindle and it solved the problem. Better feed rates and no more bit breakage.