Timeless tale... cutting aluminum

Discussion in 'Sheet Metal' started by kudo, Jan 3, 2020.

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  1. Jan 5, 2020 #21

    Aerowerx

    Aerowerx

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    I don't think the abrasive paper would matter much. Using a cutter designed for wood on aluminum, and they wear down quickly anyway. Besides, they aren't that expensive. Just buy a bunch of spares. Compared to the cost of the entire project, it would be what? 0.05%?
     
  2. Jan 5, 2020 #22

    ScaleBirdsScott

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    If you're cutting aluminum at high RPM (as with a router) Definitely make sure to use carbide endmills and definitely they are not the cheapest. Figure about $20/ea.

    Not the end of the world. But I don't like burning them.
     
  3. Jan 5, 2020 #23

    Aerowerx

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    What I was describing would not be an end mill, but something that cuts on the side, like a laminate edge trimmer.
     
  4. Jan 5, 2020 #24

    ScaleBirdsScott

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    True true, that's what you need for the router+template method. Those are still not cheap, on the order of $15-30/ea for a quality one, depending on the specs. I'd still go with a carbide cutting edge on one of these, in which case it should last a while on Aluminum as long as one isn't going absolute beastmode on it. So to do just a set of wing ribs one bit should be plenty, and so I guess on the grand order of things $20 is not bad at all. And even if you need a spare, it'll come in handy eventually for sure. Get the cheap import cutters and, well, they'll chew up quick.

    And not that anyone is suggesting it, but for sure I've sworn off any supposed 'economy' in cheap endmills at least with dealing with a high-speed router for cutting aluminum. You burn through a pack of 6 to do a job 1 quality one would have done many times over. (It just means that when you do screw up and burn a good bit it hurts that much more)
     
  5. Jan 5, 2020 #25

    MadRocketScientist

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    A good carbide endmill works wonders, I could cut all of the sheet metal for my CriCri and then some with the same carbide cutter!
     
  6. Jan 10, 2020 #26

    pfarber

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    The good thing about side cutting with an end mill is that you can raise/lower the work and get a 'fresh' cutting surface. As long as your feed rate is sane, you won't be bending anything. Al likes a higher RPM.. not sure about 20,000 rpm router speeds, but def more than steel.

    In A&P school one project is to make some ribs with lightening holes. We had wooden forms and used C-clamps to cut/file to shape then bend the flange with a hammer/mallet, used crimping pliers to remove warping. Took maybe 30 min to do on rib. We used a metal worker to punch out the lightening holes, but you can easily drill those out in many ways.
     
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  7. Jan 11, 2020 at 1:59 AM #27

    MadRocketScientist

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    I run 24,000rpm when cutting aluminium on my CNC.
     
  8. Jan 11, 2020 at 8:51 PM #28

    pfarber

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    But the key question is WHY?

    If your $300 chinese wood 3d 'cnc' only has an on/off switch, that one possible answer.

    If you can explain your tool choice, SFPM, and material selection, that's another.
     
  9. Jan 11, 2020 at 10:51 PM #29

    MadRocketScientist

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    Aluminium likes a high surface speed, much higher than steel. With the smaller cutters (1/8") the higher rpm gives the best finish. Most hand routers don't spin this fast. I can give you the numbers I use but that isn't exactly applicable to cutting aluminium with a hand router. It is quite hard to maintain a constant feed rate by hand but the spindle speed still applies. If you were cutting with a 1/2" cutter then the best spindle speed might be slower due to the larger diameter.

    I do indeed have a Chinese router but you missed two zeros off the price :p:D:eek:

    Kerosene works really well as a cutting fluid on aluminium, I have also heard that ethanol also works, but I haven't tested it myself!
     
  10. Jan 12, 2020 at 12:49 AM #30

    PMD

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    One of my former workers (building aluminum boats) now has a business making toolboxes, headache racks, welding decks, etc., all aluminum. He has a very large CNC table, and runs 1/4" milling cutters (not sure of speed and feed, but FAST) cooled by emulsion type coolant in fine mist spray. IIRC, 1/4" material takes 2 or 3 passes - no full depth cuts. Works well enough that the table runs more than a dozen 8 hour shifts a week and is reliable enough to have no backup. Just FYI: clamping is done by using a vacuum behind MDF board, masking area outside of sheet with more Al material. Would not really want to do this by hand, but with good template, probably could be done well, but I strongly suspect still with 1/8 or less depth per cut.
     
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  11. Jan 12, 2020 at 9:17 AM #31

    ScaleBirdsScott

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    My CNC router isn't a professional unit, but a homebuilt CNC jobber, so the rigidity doesn't permit me to really push the feeds enough to use 24k rpm. I run about 13k @ 20-40ipm depending on situation with 1/8 single flute. No coolant, and using spray-mount and/or screws for workholding. It does the job, there's other methods, and I've played around with some, but ultimately I'd love a pro machine with a vac table but clearly that's beyond homebuilder scope. For a single airframe, and then some, a sub-$3000 CNC router table can make all of the parts just fine, albeit with some attention paid and patience applied.

    But if I could push 100+ipm or more with a good vac table you bet I'd be pushing that spindle to the limit.
     

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