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  • newbie question about fly cutting

    I am a relatively inexperienced machinist and have a few questions about fly cutting.

    I am having to make some plates that I'm going to fixture off of and need them to be especially flat, and since I do not have a grinder I assume that fly cutting them is just as good for my purposes.

    The way that I'm thinking of making my base plates is first fly cutting the rough laser cut plates to thickness then once they're the right thickness and flat I will mill the edges to the correct profile then drill/ream/tap the appropriate holes.

    How do I go about fixturing the plates on the mill table? If I clamp them down I'm worried I will distort them and then once I remove the clamps I will still have "unflat" plates. My second question is do I use any coolant (mist) while I fly cut?

  • #2
    Dave Hyland has a clamping solution here:

    http://www.davehylands.com/Machinist...utting-Clamps/

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    • #3
      Whats the material ?
      can make a big difference in warpage.
      I assume it is mild steel since you had it laser cut.
      normally I like to fly cut a finished part to maintain the finish better.
      Can you flip the part during machining to equalise the stress ?
      To mount and support a plate that is warped, etc, , cover your mill table with
      Saran wrap, or Aluminum foil..make sure no holes.. then drop a gob of plaster of paris ( 10 minite set) on the cover, and set your part on it and allign it for clamping. Be sure it fills in all areas under the part and still allows the part to actually touch the table
      partially clamp to "hold" position only "and wait till the plaster is hard ( check the mixing pail ), then finish clamp. this will hold all deformities of the part during the milling operation. ( the plaster will rust your table if it gets to it )
      Rich
      Last edited by Rich Carlstedt; 04-13-2007, 01:34 AM.
      Green Bay, WI

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      • #4
        I'm not particularly fond of fly cutting for a precession plate unless it's a huge multi-bit tool. When someone speaks of fly cutting I think of those little one bit whirling tops. But if that's all ya got, that's all ya got.

        Yeah, material specs would help but light cuts and a coolant will reduce warpage. Side clamp a plate using "caming" hardware. Or a magnetic chuck.

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        • #5
          Originally posted by dp
          Dave Hyland has a clamping solution here:

          http://www.davehylands.com/Machinist...utting-Clamps/
          Just what I needed for my project. I'm making a set of these today

          thanks for the link

          pete

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          • #6
            Originally posted by slowtwitch
            Just what I needed for my project. I'm making a set of these today

            thanks for the link

            pete
            I second that. These clamps look very useful. As for material It is just hot rolled steel. Yes all I have is one of those 1 bit whirly things, but I figure that is better than a bunch of passes with a 3/4" end mill. As for the cutting depth how light is light?

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            • #7
              flycutting a large flat surface of bar stock is not as simple as you'd first think. you face two problems 1) that material could bend like a banana once you start cutting it. The is because the rolling creates stresses in the metal, concentrated in the outside sections, and when you cut off some on ones side you change the dynamic and new equilibrium is found. This is most prevalent in cold rolled, but is there is most material 2) when you clamp it, the clamping force distorts the relatively wide/long thin piece so after the clamping force is removed it springs back to its original shape.

              The best option is to use stock of the right thickness. if you can't, here are some options. Use hot rolled, it has less stresses. Get the piece normalized, this removes most of the stresses (and it will look like hot rolled). go back and forth, side to side removing material from each. This at first removes the more stressed outer portion and then corrects the resultant bending. you have to be careful that the clamping is not temporarily holding an otherwise warped piece flat. Rich gave a good suggestion on how to do this, I'd heard it using bondo. feeler gauge and shims would work as would a file/scraper and surface plate to make sure where the material is being clamped is flat.

              Of course, if it's just a gusset to be welded in a tractor bucket, have at it. but if you need to get this piece accurately dimensioned and flat, those ideas should help
              in Toronto Ontario - where are you?

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              • #8
                Those are intresting clamps. Has anyone made larger ones, ie. for a Bridgeport
                table ? The foundry kids at school use a Bp to remove the "runners" ( is that
                the term?) from their castings. They have a time trying to hold odd shapes in
                a mill vise. So I was thinking that those clamps might be the ticket to hold
                such on the table. Or any other ideas?
                ...lew...

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                • #9
                  I agree! I will be making a set of those clamps as well.
                  Their perfect for the small scale I work on. My fly cutter is home made as
                  well, from a print I found online.

                  A large end mill woundn't give me the finish I wanted, so I improvized.

                  Rick
                  Home Model Engine Machinist

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                  • #10
                    Originally posted by Lew Hartswick
                    Those are intresting clamps. Has anyone made larger ones, ie. for a Bridgeport table ?
                    It's basically a home-brew version of a toe clamp. I use these toe clamps from MiteeBite on my knee mill:


                    I also have these eccentric hex clamps from MiteeBite, which are great:


                    The toe clamps would be a good shop project.
                    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                    Comment


                    • #11
                      Originally posted by lazlo
                      It's basically a home-brew version of a toe clamp. I use these toe clamps from MiteeBite on my knee mill:


                      The toe clamps would be a good shop project.
                      Lazlo,

                      Tell me about the action of the toe clamps. Does that come from an eccentric or an angular pull-down? In the picture it looks like the piece that does the clamping is at a slight downward angle to the table, so a pull-down would be going the wrong direction unless the tapped hole is angled the other way.
                      .
                      "People will occasionally stumble over the truth, but most of the time they will pick themselves up and carry on" : Winston Churchill

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                      • #12
                        If the center screw is eccentric as it is on their standard myteebite clamps, then the eccentric rotation of the head would move that sliding top piece both in and down at the same time due to the angular surface it slides on. This is something that the others do not have and I would think would be a real advantage to that design.

                        Paul
                        Paul Carpenter
                        Mapleton, IL

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                        • #13
                          Originally posted by TGTool
                          Tell me about the action of the toe clamps. Does that come from an eccentric or an angular pull-down?
                          On the MiteeBites, the button-head cap screw is eccentric. So you snug up the t-slot nuts to the workpiece, and then tighten the cap screw, which pushes the toe down into the work. The toes are reversible -- one side is smooth, the other size is serrated.

                          The MiteeBite hex clamping nuts work the same way (eccentric screw).

                          On a classic tool and die toe clamp, there's a 45° dovetail, with a hex cap screw. As you tighten the screw, it pushes the toe down at a 45° into the work.

                          It may not look like it, but these clamps are rock solid.
                          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                          • #14
                            Deferr: I don't know what type of mill you have, but if it's a B-port/knee type be aware that having your head a bit out of tram affects fly cutting a couple of ways. Some guys, looking for finish appearance only will leave it a bit out sideways so only the leading edge cuts(no dragging on rear of F/C). This ,however, leaves a slight scallop or concave shape to the surface. It's obviously not flat. In that respect, a 3/4" endmill will leave more swirls, but the concavity will be less dimensionally (word?). If you have a mill drill tramming is possible, although not the same method as a conventional mill.
                            I'm not sure of you tolerances or equipment, but thought you'd like to know. Good Luck
                            I bury my work

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                            • #15
                              The mill is a retrofitted NC mill. Is using a 3/4" end mill a bettter way to go since any error in the angle in the head is not magnified by a large "reach"? I don't care about surface finish as much as I do the two sides being parallel and flat.

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