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  1. #1
    Are there special drill bits needed for a cnc?

    I know my spindle has certain collet sizes so standard bits are unlikely to fit.

  2. #2
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 4 Hours Ago Has been a member for 5-6 years. Has a total post count of 1,186. Received thanks 85 times, giving thanks to others 54 times.
    Get good quality bits and get your speeds / feeds right.

    If you have the typical 24K RPM low torque spindle, its more difficult. Small holes are OK, large ones you will struggle.

  3. #3
    Quote Originally Posted by Chaz View Post
    Get good quality bits and get your speeds / feeds right.

    If you have the typical 24K RPM low torque spindle, its more difficult. Small holes are OK, large ones you will struggle.
    how about fitting them in the colet? Are you talking about bog standard drill bits or do they have special bits for cncs?

  4. #4
    Quote Originally Posted by dfox1787 View Post
    I know my spindle has certain collet sizes so standard bits are unlikely to fit.
    You could throw us a bone and tell us so we don't have to guess or assume?
    You think that's too expensive? You're not a Model Engineer are you? :D

  5. #5
    Quote Originally Posted by magicniner View Post
    You could throw us a bone and tell us so we don't have to guess or assume?
    lol ok max collet size 12mm. Im only asking if there a special drill bits for cnc
    Last edited by dfox1787; 22-05-2018 at 09:14 PM.

  6. #6
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 2 Hours Ago Has been a member for 9-10 years. Has a total post count of 2,100. Received thanks 232 times, giving thanks to others 5 times.
    Drill bits are not specific to CNC, however you do get lots of options which may suit a particular application far better.

    Have a browse of the Phantom Drills website, and try finding a copy of their catalogue if you want to see just how many options are available.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  7. #7
    Wal's Avatar
    Lives in Stockport, United Kingdom. Last Activity: 4 Days Ago Has been a member for 6-7 years. Has a total post count of 387. Received thanks 41 times, giving thanks to others 18 times.
    >I know my spindle has certain collet sizes so standard bits are unlikely to fit.

    Why not - you're using an ER system, aren't you?

    Anyway, as m_c said, there are plenty of options out there - a cursory search brought this up:

    https://www.cadem.com/single-post/cn...l-helix-angles

    Not a bad place to start. As per Chaz's advice - yep, it can be a bit hit and miss with the 2.2kw Chinese spindles - you don't want to go too fast and burn up the drill, but you really don't want to drop much lower than 9krpm as you risk stalling the spindle...

    One thing I would say: make sure you spot drill first..! If you're using standard drill lengths then you can expect a bit of a squeal on the first peck, but that should disappear once the drill gets a bit deeper... Here's a vid of my machine drilling out a section so that I wouldn't have to deep slot (fast forward to about a minute in). I'm sure I could've gone a bit quicker, but you know - when you find something that works you tend to keep it that way..!



    Good luck.

    Wal.
    Last edited by Wal; 24-05-2018 at 07:22 AM.

  8. #8
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 2 Hours Ago Has been a member for 9-10 years. Has a total post count of 2,100. Received thanks 232 times, giving thanks to others 5 times.
    For general purpose drilling, I'll normally get Cobalt drills. More durable than pure HSS, but typically slightly more brittle (not as brittle as pure carbide though!), and can handle higher speeds than pure HSS (but no where near as high as pure carbide).
    Polished ones for aluminium, and suitably coated ones for steel.

    Key thing is to ensure you are within the speeds/feeds specs for the drill, and as Chaz/Wal say, with Chinese spindles that can be a problem. You'll likely get better results on larger holes by either pre-drilling then milling to size, or just helix milling.

    Spot drilling depends on what you're doing. I generally only use stub drills with split point (or whatever the manufacturer wants to call their self-centring drills), which I'll never spot drill first. However anything I need to use any longer a drill on, I'll generally spot first.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  9. Hello,
    Drilling accurately placed holes is not easy. I strongly suggest screw length bits, the shorter the better, to eliminate deflection. I'm fairly new to cnc and posted a video of my experiences drilling holes here: https://www.youtube.com/playlist?lis...jVPFZmTCBEeF2y
    I should add that I bought an old 3/8" Jacobs chuck off of ebay and a straight 1/2" shaft for it. I chucked it up in a precision collet on the router and damn if it doesn't work perfectly. For drilling operation, no more changing collets or needing collets for every different size. I highly recommend it. I show it in the video I linked to above.
    Cheers, Tyler
    Last edited by wiremonkey; 23-05-2018 at 05:30 PM.

  10. #10
    I use a mix of 3mm HSS twist drill in a standard 3mm collet to pilot holes (no spot drill), and then finish on the drill press. Or interpolate holes using a 6mm end mill ideally with a spiral toolpath. Fusion is great for this.

    These end up being very accurate although for bolt clearance holes I often go for bolt nominal diameter plus 0.5 mm to give some allowance in assembly.

    See examples in my videos here:

    4:40 and 10:40
    https://www.youtube.com/watch?v=wqff3IZZWvw
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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