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Punch and flare tool...but smaller?

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  • Punch and flare tool...but smaller?

    I've recently used a screw-driven hole punch and seen that some exist that also flare the hole or just flare an existing hole.

    In thin sheet metal like computer cases the holes are presumably punched on large hydraulic presses. The holes these make are flared out at the back and when tapped you get more threads than the thickness of the metal would otherwise allow for. I'd like to be able to replicate that if possible. I'm thinking about M3 or 6-32 size - nothing I'm hoping would need the hydraulic press I've not got room for!

    Does a smaller maybe hand-powered device exist? Ive looked but maybe I don't know the magic terms to search for.

  • #2
    For that sort of size a screw driven hand tool should be fine. You would not be moving a lot of metal or swaging it so much that the force needed could not be had from a screw driven hand tool.

    When you say "flaring tool" I'm guessing that you mean a tool that forms a conical countersink in the sheet metal? That one would be easy. The other would be harder since I suspect it wants some swaging down then pushing back to shrink the upset portion to a thicker wall. At least that's what it feels and sort of looks like in a computer case I've got here.

    The smaller metric stuff would lend itself to this far better than the relatively coarse 6-32 size. 6-32 being the "coarse" size in a Special screw size. So it would be hard to get more than a 20 to maybe 30% thread in the sheet metal. Easier to find the computer friendly metric sizes in 2.5 and 3mm and go with those.
    Chilliwack BC, Canada


    • #3
      This is not exactly what you were asking for, but take a look.
      Nutserts were designed to work on sheet metal and this set includes M3 and 6-32 sizes.


      • #4
        Aircraft sheet metal countersink punch dies and dimpling tools. They come in many forms, some use a hand held pop rivet tool, some a dedicated tool, as I said many forms. All will be on this site or from Aircraft Spruce.

        Hand Riveting & Dimpling Tool Our hand rivet & dimpling tool is used for hand dimpling of skins and small parts and for hand riveting of parts, assemblies, and spars. This tool maintains alignment of the dies to each other, and insu


        • #5
          You may be over thinking this situation. To extrude the metal out the back side to increase the length of thread engagement we make the tap drill hole way undersize and use a thread forming tap. The form tap extrudes the material. A cutting tap doesn't work as well since it may just cut the excess material away without appreciable extrusion. It may take a few tests to determine the best hole size.


          • #6
            Cheers guys.
            BCRider The harder of those options is basically what I'm trying to be able to do. 6-32 UNC is one of the common PC screw sizes - the other being M3 because obviously, there's nothing like sticking to one common standard!

            This is the kind of result I'm after....although this is a much more refined version and definitely not the process for me!

            Also looks like it can be done with flow drilling and then tapping...but again I think that's perhaps above and beyond what I had in mind and may be necessary for a tiny hole. I think that cases tend to be in something like 0.7mm sheet steel and the back of the holes look ragged like the hole has been punched through, not with a sharp tool that cuts the circle but fairly blunt that punctures it after having deformed it out the back.

            mikey553 I'm not sure what I've really got against nutserts, rivnuts and thread inserts to be honest...but definitely something. Maybe I feel it's cheating. That $40 tool is also a hundred bucks over here - there are, of course, the usual import offerings for closer to $40.

            vectorwarbirds I'll have a good peruse of what they do for future reference but I think those dimple dies are more for creating a countersink to make the head of a screw/rivet flush with a panel rather than to deform it backwards to get more effective thickness of material to hold threads.

            @DR That's interesting. Definitely up for testing that. I've got a form tap in M3 because I'd already found that it gave a more reliable thread in thinner materials like this. How much undersize are we talking? About the normal cut tap drill size (2.5mm) rather than the larger form tapping drill size (3.2mm)? Does it need something backing the hole to avoid deforming the rest of the panel....or am I over-thinking it yet again?


            • #7
              Regular punch, oversizef die doesn't work? Makes a dimpled hole for me every time.


              • #8
                metalmagpie Another interesting idea. I've not tried it because I haven't got the tooling. It seems that such things are available in any system you long as it's imperial. Converting the smallest 3/32 and 1/8" to metric gives 2.38mm and 3.17mm which isn't far off the cut-tap and form-tap drill size respectively. I don't suppose you've tried it with an M3 by any chance?
                Options seem to be a 2nd hand Roper Whitney Jr No5 or a new Kennedy clone of it for half the money that might be worth a punt.


                • #9
                  Spot weld a piece of steel onto the PC case or enclosure. Would it require more power than a batery tab welder? Build a spot welder from a MOT.


                  • #10
                    You are talking about an extruded thread feature in sheet metal.

                    You need high force to get the material to plastically flow like that. I don't think that you could do it in a No5 hand press, and if you did you'd probably get the punch stuck in the material and grenade the tool on the retract stroke.

                    There are "flow drills" which can heat and smush metal out into a boss, but they require quite a bit of spindle hp and rigidity to work.


                    • #11
                      Originally posted by reggie_obe View Post
                      Spot weld a piece of steel onto the PC case or enclosure. Would it require more power than a batery tab welder? Build a spot welder from a MOT.
                      Yes it would require orders of magnitude more energy tham a battery tab welder can supply. Nickel foil is often somewhere between .005-.020 thickness. If you wanted to get threads in that didn't torque out if the mating screw galled or stuck at all, you'd need something more like a large 240V 20A powered spot welder. Might as well arc weld the part on.


                      • #12
                        Extruded Holes: If you've ever taken apart pretty much anything modern with screws in it you will find you get dozens of screws and no nuts. There are two types of screw used in this situation (well, rather more than that, but this is a very general point). Self ta…


                        • #13
                          Something like this?
                          Formdrill: Thermal drilling experts. Friction is used to produce a bushing that can be tapped afterwards. Also know as Flow drill process, Frictiondrill process.
                          Helder Ferreira
                          Setubal, Portugal


                          • #14
                            Epoxy a nut or tapped piece of steel to the skin of the case. Done!


                            • #15
                              Everything depends on the thickness of the metal sheet used, if there is room, then rivnuts would be an easy option.