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  1. #1

    Join Date
    Apr 2020

    Breaking carbide tool

    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!

    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!!

  2. #2
    Join Date
    Jun 2013

    Re: Breaking carbide tool

    Max it looks like you hit something in the old bit of plywood. Your feeds and speeds are high, but I'm not going to comment on them further. If I cut timber I normally run around 1200mm min at 10 to 20k rpm. But timber is really forgiving. Carbide is brittle but hard. Is there a chance you dropped the end mill?

    Mate. If I bought a carbide end mill for $$ and ran it like you had. Had definitely not hit anything. I would be sending a pic to the supplier.

    Sent from my SM-N970F using Tapatalk

  3. #3
    Gold Member
    Join Date
    Apr 2004

    Re: Breaking carbide tool

    How were you holding the plywood down? An upcut tool with spiral flutes like that will tend to pull the plywood up from the bed a little, then the clamps pull it down again. This causes instability in the cut that can damage cutters, particularly if the whole setup isn't very rigid. Coupling that with the abrasive and uneven nature of plywood, the ambitious DOC and speeds, and the fragility of those little edges on your cutter, and it's not altogether surprising this happened, Maybe Kyocera would have some good advice for you if you contacted them.
    Andrew Werby

  4. #4
    Join Date
    Jun 2013

    Re: Breaking carbide tool

    Agree with Mr Awabe. Although I do have to point out we are talking Carbide here. And Ply can only be so hard even the epoxy or a tight knot. I've never ever ever chipped a Carbide tool on any timber based product. In 30 years.

    Yep. Contact the supplier.

    Sent from my SM-N970F using Tapatalk

  5. #5
    Join Date
    Nov 2013

    Re: Breaking carbide tool

    carbide is wonderfully hard but it can be overheated. I would not expect plywood to bother your tool....but it has.
    Have a close look, is there any discoloration that suggests heat?

    Breaking tools is a hazard....and you will break a lot before you are through. Most of my tools are very small, say 0.5mm two flute endmills,
    through to 1.5mm and 3.125mm four flute endmills and drills from 0.3mm to 3.125mm, mainly for PCB manufacture and small parts in
    plastics, brass and aluminum. I buy in lots of ten, and in cases where I use a lot, say 0.5mm endmills or engraving tools, by lots of 50.

    It seemed at the beginning that I could not get 1/4hr out of a 0.5mm endmill, now I get 8 hours plus before I discard them for being blunt,
    when I don't break them outright by doing something stupid.

    I'm cutting soft metals in the main....PCB is when all said and done thin copper (53um) plates glued to a fibreglass substrate. One thing you must absolutely
    avoid with any tool and any material, but especially soft and sticky metals like copper and aluminum is recutting chips. It causes Built-Up-Edge on the tool and breaks it
    toot-sweet. Use compressed air, vacuum, mist cooling, flood cooling or whatever to get the chips out of the cutzone, especially with metals, but ANY material.


  6. #6
    Join Date
    Jun 2013

    Re: Breaking carbide tool

    0.5mm endmill. Have you ever filmed that in action on macro macro? I wonder if it spits out a tiny little rooster tail of chips like my 14mm one does haha

    Sent from my SM-N970F using Tapatalk

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