Breaking carbide tool

[Maxomous]

Hi everyone,

I'm a bit new to the CNC routing world and am having issues with my cutter getting badly damaged.

I have built a 3 axis CNC router with a generic 24000RPM ebay Chinese spindle using GRBL as my controller.

Everything is running well now however I have just started trying to do some test pieces on some old plywood. I got myself a cutter from msc, an upcut Kyocera p/n 91113 - a 6mm, 2 flute, carbide cutter designed for wood and plastics. Here's the datasheet: (https://www.kyocera-sgstool.com/uplo...outers_PDF.pdf)

It suggest <=1*D doc @ 31805rpm & 4135mm/min

My spindle can only go at 24000rpm so I calculated that to be 3120mm/min, and I did a doc of 6mm

Thing is when I ran this today for about half an hour, although it seemed like it had cut everything well, I pulled out the cutter to find the tips had sheared off - see attached image... And no it's not a rad cutter!

image

So far my guess is either
- too high doc
- too low spindle speed (as Vc is 452 with my feed/speed whereas datasheet recommends 480-720)
- should stick with hss
- machine is f****ed / too much vibration or something

I would do more tests but don't want to keep breaking these cutters as they're not cheap!

Please help,
Thanks in advance!!
Max

[JAZZCNC]

It should cut like butter through plywood with those settings provided the machine is stiff enough and this is probably where your trouble lays.
Carbide likes to take nice big cuts and often isn't pushed hard enough but it's also brittle and doesn't like vibrations so really needs a good strong spindle and machine.

Also, I suggest you forget the recommended speeds n feeds if your machine is weak because they are based on industrial-strength machines with high HP spindles so you can't really use them anywhere near what they suggest.

I can not make any accurate suggestions regards speeds n feeds and neither can anyone else unless they know your machine. All I can say is that it's safer to start low and work up and listen to what the machine is telling you. Get to learn it's language and it will let you know when it's unhappy.

My main suggestion is to start with 50% tool diameter DOC as it's safer and see how it goes from there. Play with feeds n speeds until it's happy then look at increasing DOC and adjusting F&S accordingly.

[dazp1976]

I've not had much luck with carbide on a mill.
I can't get much doc and they don't like to be hogged.
I found that if I take a lower doc I can run faster without problem.
Ended up the time difference wasn't much.

I know I'm on about a mill but, f - s - doc - chipload - sfm, it's all the same.

[JAZZCNC]

I've not had much luck with carbide on a mill.
I can't get much doc and they don't like to be hogged.
I found that if I take a lower doc I can run faster without problem.
Ended up the time difference wasn't much.

I know I'm on about a mill but, f - s - doc - chipload - sfm, it's all the same.

Your probably not pushing it hard enough, carbide likes to be worked hard but it does require the spindles as enough HP.

[Maxomous]

Thanks for your responses, I will give the speeds/feeds a play with and see how I get on.

On inspection, I found a couple mm chunk of metal embedded inside the spoil board, I'm starting to think that could have been the problem but I'm not entirely sure...

Think I'm going to replace the board anyway to be safe.

I did question whether any of the old ply may have had a tiny nail or something...