Welcome to Our Community

Some features disabled for guests. Register Today.

Choosing End Mills

Discussion in 'General Talk' started by kbcustoms, Jul 4, 2017.

  1. kbcustoms

    kbcustoms New
    Builder

    Joined:
    Jun 23, 2017
    Messages:
    6
    Likes Received:
    0
    Hi all,

    Im very new to the Openbuilds arena and have just ordered my first CNC machine via Ooznest.

    I will mainly be cutting MDF, potentially up to 18mm and acrylic to 5mm. Now the kit I purchased included the Dewalt 26200 and I have been looking for good end mill sources in the UK if possible. I understand that with the router being 1/4 collet that 6mm mills wont fit, I need 6.35. I have also ordered the 1/8 collet but again due to using imperial measurements 3mm mills wont fit, 3.175 is what I need.

    So if anyone would be good enough to point me in the right direction, I would like to make some quite detailed profile toolpaths where I would need down to 2mm cutting end. I have looked on Amazon, Ebay etc but if you know of anywhere that would be better please let me know.

    My main requirements are 2mm, 3mm and v carve 60 degree

    So far I found these:

    Konmison 10pcs Router Bit 3.175x17mm 2 Flutes Spiral Bit Milling Tools Carbide End Mill for CNC Router Engraving Machine: Amazon.co.uk: DIY & Tools

    Thanks in advance, look forward to hearing from you all.

    Kris
     
  2. Rob Taylor

    Rob Taylor Veteran
    Builder

    Joined:
    Dec 15, 2013
    Messages:
    165
    Likes Received:
    40
    Collets shrink as you tighten them, that's what they're for. I'd try the 6mm in the 6.35 and the 3mm in the 3.2, just in case. If the relief slots in the collet bind up before it puts pressure on the tool shank, then yeah, it's too big. "Real" collets (ER32, 5C, R8, etc) have ~1mm or so of actual capacity for using undersize or out-of-system sizes. Obviously the smaller the collet the less room it has to shrink, but you might get lucky.

    As for sources, I no longer live there, so I can't help you with that one. Axminster was usually a good bet for quality (at a price) but Amazon/eBay will probably be fine for getting started in soft materials.

    MDF can use regular 2-flute mills with aggressive cuts. Acrylic, especially extruded rather than cell-cast, is more finicky. I'd probably try and find a 4 or 5 flute mill, run at high speed, moderate feed, and keep some kind of coolant handy that won't craze or frost the plastic. It likes to get melty and/or crack. Best thing for acrylic is actually CO2 laser light. Someone here who CNC cuts acrylic plates might be more use on that though, my experience is more traditional machining.
     
    crispin likes this.
  3. kbcustoms

    kbcustoms New
    Builder

    Joined:
    Jun 23, 2017
    Messages:
    6
    Likes Received:
    0
    Thanks for your reply Rob.

    From what Ryan Lock said over at Ooznest, its not looking good to take the slightly smaller bits in the Dewalt :( Il certainly give it a go just in case though!

    Il order a pack of the Konmisson, at £1 each its certainly worth a go.

    If anyone else want to put forward suggestions I would be more than happy to hear from you.
     
  4. Kevon Ritter

    Kevon Ritter Veteran
    Builder

    Joined:
    Apr 30, 2015
    Messages:
    114
    Likes Received:
    35
    1/4" and 6mm may look close enough, but I wouldn't dare putting a 6mm shaft into a 1/4" collet. You may be able to get away with it for 1/8" and 3mm.

    You will always be able to find an endmill for your collet in whatever type.

    I would do the exact opposite of what was suggested for acrylic. Infact, what was suggested would cause serious harm (from my experience) Acrylic cuts easy when you can remove material, which decreases heat. More flutes does not help remove material. With acrylic, I use a 3mm o-flute at about 20k rpm. 1000mm/min feed works perfectly fine for me. For a finer finish, You can turn your feed down to about 75-80%, but keep an eye on it. I can easily cut at 2mm depths, but much more and holding the material becomes the challenge.

    He's using a router, not a low rpm spindle. My intention was not to be disrespectful.
     
  5. Rob Taylor

    Rob Taylor Veteran
    Builder

    Joined:
    Dec 15, 2013
    Messages:
    165
    Likes Received:
    40
    Specifically a rotary tool/router collet, sure. They don't have much range of motion. Real 1/4" collets will happily take 6mm tools, I do it frequently. Even an ER-25 should, though I'm not sure about ER-20 and down. Might be a little tighter at that size.

    No worries, that's specifically why I mentioned that my experience was in traditional machining- ie. 2000rpm and below. For that, to reduce the chipload per tooth (and reduce shock load on a brittle material on each tooth pass) the flutes get bumped since the RPM can't be. The higher flute count isn't to remove more material specifically (though it would technically allow you to increase your feed rate for HSM), but to allow you to take the same material in smaller bites. For HSM, I'd imagine the opposite is true. You're taking very small bites almost to the point of merely rubbing, so whacking the feed up to get the chips flying is critical.

    That said, removing heat with material always applies to everything, if only for dimensional stability. I'm not sure what you mean by 0-flute, since that would just be a round shaft, but at 20k revs, I'd imagine even a 2 flute could be quite sufficient depending on feed rate, though low tooth counts on a low-precision spindle combined with a brittle material would make me nervous. As always, the triangle of flute count, speed and feed should be calculated out for what you're trying to achieve. I imagine there's also a difference in the machining data for extruded vs cast acrylic, but I'd also guess it would vary depending on flute pitch, flood/mist/thru-coolant, material thickness and workholding, etc etc. Plastics are tricky, I'm happier doing metals! :p

    Often the best option as used on CNC centers in industry is the old "tighten till you hear the crack, then back a quarter turn"- ie. trial and error during the part setup phase, just keep turning everything up until something breaks, then drop it back down again to where it was good, and then you know you're near the limit of the setup and getting maximum capacity from the tool, rather than babying it and losing out on potential cycle time gains. Different machines may prefer feed over speed, or vice versa, depending on the components used, so playing around a bit is usually a good idea anyway, even when you've calculated the theory.
     
  6. Kevon Ritter

    Kevon Ritter Veteran
    Builder

    Joined:
    Apr 30, 2015
    Messages:
    114
    Likes Received:
    35
    "oh"-flute, not quite zero-flute :D
    Much different profile made to literally scoop material. They work great on higher rpm or heat sensitive materials.

    As for the collet, you can, but do you really need to? You can always find your mill in whatever shank diameter.
     
    Rob Taylor likes this.
  7. Rob Taylor

    Rob Taylor Veteran
    Builder

    Joined:
    Dec 15, 2013
    Messages:
    165
    Likes Received:
    40
    Just looked them up. Very handy! Gotta keep those in mind for the next CNC build after the one I'm about to start.

    Right now I only have a short set of imperial R8 collets and a random mix of ER32 collets, so it's generally the case that I have to just find the closest workable option. A complete range of R8 and ER32 (plus other, future spindle tapers) collets is a small fortune!
     

Share This Page

  • About Us

    The OpenBuilds Team is dedicated helping you to Dream it - Build it - Share it! Collaborate on our forums and be sure to visit the Part Store for all your Building needs!
  • Like us on Facebook

  • Support Open Source FairShare Program!

    OpenBuilds FairShare Give Back Program provides resources to Open Source projects, developers and schools around the world. Invest in your future by helping others develop theirs!

    Donate to FairShare!