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Cutting

Discussion in 'CNC Mills/Routers' started by Steven Bloom, Dec 28, 2015.

  1. Steven Bloom

    Steven Bloom Veteran
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    Well the Sea-Ox is nearing completion and now I am at a point where I know almost nothing. So my first questions is the following. I am using a router that uses 1/4" inch bits by default. Should I get a adapter that fits around 1/8" bits or use an adapter that is more like a drill chuck and can be adjusted. 2nd question. What kind of bits do I need for certain types of materials. I plan to cut aluminum, carbon fiber and wood. What kind of bits do I use for each one.

    Thanks and sorry for the dumb questions.

    Steven
     
  2. Steve Fox

    Steve Fox Veteran
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    I use an adapter for 1/8" bits.
    Not really good having drill chucks moving that fast, in my opinion and can be hard to keep tight.
    Just adds to rotating mass, too. I bought my adapters for around $10 each.

    I never cut carbon fiber, but I use mostly milling machine bits for wood and aluminum.
    I also use circuit board drill bits. They come in multiple sizes with 1/8" shanks and work great for drilling as well as small cutting, as in text or small parts. I have them from .3mm to 2mm. I also have a bunch of 1/8" cutters.

    All are extremely inexpensive.
     
  3. Steven Bloom

    Steven Bloom Veteran
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    what kind of bits are you using for wood vs /circuit boards vs aluminum ???

    Thanks Steven
     
  4. Florian Bauereisen

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    HI,
    i would use a 1/8 bit adaptor simply for runout of most drill chucks...

    For carbon i use burred type of bits, high revs and very slow cutting speed as well as a very slow plunge.
    Aluminum is best cut with a single flute aluminum specific bit (has a polished channel and geometry)

    Wood usually is cut with 2flute bits.

    greets

    flo
     
    Steven Bloom likes this.
  5. Steve Fox

    Steve Fox Veteran
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    I cut wood with all of them.
    I mostly cut aluminum with milling machine bits (end mills), but have used carbide tipped router bits, too.
    For Baltic Birch plywood, I use those burr type 1/8" bits, but I have used end mills for that, too.
    They just don't last as long.
    The only thing I haven't done is cut aluminum with the burr type bits.

    It's been my experience that diameter matters more than type for general cutting.
    Once you get the Ox done, buy several of each type and start cutting.
    You'll figure it out. I've used every type I've bought.

    I haven't cut any circuit boards.
     
  6. gotswrv

    gotswrv Journeyman
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    You'll need to pay attention to loaded RPM and look up suggested speeds and feeds for your bit and material. All cutters and materials have a working range. Some materials, like aluminum and plastic are more forgiving than others like D2 or Inconel.
    Most general use endmills cutting aluminum in the 1/8" - 1/4" range fair well with .0015-.0025" per tooth, per revolution. So if your loaded RPM is 10,000 you'll want to be moving at 15-25 inch/minute PER tooth. So two flutes is double that speed, this numbers are on the slow side(push much harder on the real CNC's at the day job).
    Going too slow will overheat the material and it will melt to the cutter or in the case of the tougher alloys get really hard and break your cutter. Woods will burn, composites will wear the cutter down quickly. Going too fast will fill the cutter to a point that it packs with chips and breaks. Or in the case or deep cuts or harder materials, the end mill just breaks.
    With DIY/ hobby machines rigidity plays a much larger role in cut quality. In short harmonics will be a noticeable factor. You will have to experiment with cut depths an feed rates to the most out of your machine.
    Ohh, general rule of thumb is 1/2 cutter diameter for a depth of cut. Plastics generally afford you deeper cuts. Plunge feeds need to be 1/2 or less (pre-drilling is a good thing) or ramp into the material at a reduced rate is better. I would expect that dropping to 1/4 diameter depth of cut might help a lot of the machines in cutting metals.
    Burr bits are great for composites, can easily pack and or gauld with plastics and aluminums.

    Now, for the question asked.. Drill chucks are not intended or well suited to side load. They are also typically not very concentric. Use the collet when needing smaller than the 1/4"
    Second part of what matters, keep it as short as you can. The longer the distance the cutter is from the spindle, bearings, rollers, beam, etc... The worse the harmonics, and deflection. Short and stout is one of the most important things to remember when machining.

    If this makes zero sense I'd suggest finding a recommended feeds and speeds chart and a SFM IPT calculator app. (search "machinist" in your apop store)

    Hope that helps get you started
    Sam
     
  7. Jonny Norris

    Jonny Norris Veteran
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    You will likely find over the years the jobs you tackle and the tooling available will require you purchase a few more collets than just the two.
    Especially when it comes to drilling, you could spend a fair deal on 1/4" 1/8" shank drill bits over time. Depending on how much drilling you intend on doing it may be cheaper for you to try to get all the available collets so as to bring standard drills back into play.
     

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