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Fly cut or drill first?

Discussion in 'A BEGINNER'S FORUM (Learn How To Machine Here!)' started by gradient, Jul 4, 2017.

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  1. gradient

    gradient United States Gradient Registered Member

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    Need to make a plate with several hundred holes from #4 to #10 sizes in aluminum 1/2" plate. I would also like to fly cut the surface so it is pretty flat. Is it better to drill all of the holes first or do the fly cut then drill. I'm guessing doing the fly cut last might cause smearing as the tool crosses the holes. Any comments?
     
  2. mikey

    mikey Active User H-M Supporter-Premium

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    Personally, I would fly cut first so I have a clean flat surface to work with. If you use a spotting drill first I suppose it doesn't really matter. I assume you plan to chamfer every hole so smearing isn't an issue if you decide to drill first.
     
    royesses likes this.
  3. RJSakowski

    RJSakowski H-M Supporter - Premium Content H-M Supporter-Premium

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    I have noticed that fly cutting across a hole will sometimes create some visual artifacts. If appearance were a concern, I would fly cut first and then drill and chamfer/deburr.
     
  4. joshua43214

    joshua43214 Active User H-M Supporter-Premium

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    fly cut first, so you can chamfer last
     
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  5. randyjaco

    randyjaco Reserved Active User H-M Supporter-Premium

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    +1 on fly cutting first

    Randy
     
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  6. westsailpat

    westsailpat United States H-M Supporter - Premium Content H-M Supporter-Premium

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    Fly cut first , spot drill a little OS then you don't have to go back and chamfer .
     
  7. Wreck™Wreck

    Wreck™Wreck United States Active User H-M Supporter-Premium

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    If strength is not a concern use a material intended for this purpose such as Alcoa MIC 6 jig plate, it has already been milled flat before you buy it. It will also stay that way after drilling hundreds of holes in it.

    A piece of easily available 6061 aluminum stock may behave in ways that you are not expecting after facing and drilling many holes in it.

    Had to straighten 4 parts made from 1 1/2" X 1/4" aluminum bar stock last week, they had 85 6-32 holes off center on a single 1/4" face, one part held in 3 Kurt vices in a Fadal 4020 VMC, they warped badly in 2 planes. Relieving the stress from one side is often bad news.

    https://www.onlinemetals.com/merchant.cfm?pid=7805&step=4&showunits=inches&id=309&top_cat=0
     
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  8. gradient

    gradient United States Gradient Registered Member

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    Thanks all. Looks like the consensus is fly cut first. Sounded right but I just needed some input from more experienced folks.
     

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