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  • small hemispherical cutter

    I'd like to find/make a small cutter that will put a roughly hemispherical head on a Olympic rivet; the commercial tool is $200 which is a little steep. What I need is essentially the reverse of a 7/16" ball end mill. Only a portion of the sphere is needed, as the rivet head is only 5/16" in diameter.

    Is such a thing made? I can see my way clear to making the blank for the cutter w/ my homemade up & over radius gadget, but I'm not sure how to get the teeth on there.... and just the bit for the commercial tool is $150 or so...

    In case anyone is curious, we're working on a 1971 Airstream - lot of small
    projects, and these rivets install like pop rivets but look like the original buck style - handy for repairs w/o removing all the interior skins.

    Ideas appreciated - thanks!

    - Bart
    Bart Smaalders
    http://smaalders.net/barts

  • #2
    Iv seen radius cutters
    Even got a set of cheapos for like $100 (like a 10 peice set)

    You could use one of those while turning the rivet in your vice on a rotary table...

    Iv seen concave cup 'grinding' stones, I believe are for gringing the ends of rods and pipes (deburing them anyway), and I know you can dress a concave into normal stones too.. but you probley want to cut not grind.
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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    • #3
      Rivet in lathe chuck and HSS tool freehand ground to shape?

      Or if I'm missing something about how to apply said cutter then get a ball nose cutter of the right diameter, feed it into the end of a piece of drill rod / silver steel to form the shape you want.
      Then mill a flat on it so 1/2 the shape from the side is removed and you have a 'D' bit.
      Heat to cherry red and quench, don't bother tempering for alloy it will hold up better.
      Light grind on the flat face of the D and fit to whatever is going to spin it.

      WD40 or kerosene as lubricant.

      .
      .

      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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      • #4
        Once upon a time when I wanted a hole with a spherical bottom to it I got a drill bit (6mm) and ground that. It worked. If you are wanting the opposite can you find a grinding tip of the right size and use that to grind a cavity into the end of a drill bit the right size? You would then have to fiddle a bit with a die grinder/ dremel to provide some relief to the cutting edge bit if you are only shaping Al, you might not have to worry too much. The only issue may be that as you would not have a chisel point in the middle, the depth of cut is limited to the cavity radius - would that be a problem?

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        • #5
          Same as Sir John but I'd remove two opposite quadrants so it's similar to a wood "plug" cutter.

          Regards Ian.
          You might not like what I say,but that doesn't mean I'm wrong.

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          • #6
            I agree with Sir John, form tool in the lathe.
            Paul A.
            SE Texas

            Make it fit.
            You can't win and there IS a penalty for trying!

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            • #7
              The lathe would be a great approach, but these blind rivets need to be installed before the rivet shaving operation forms the profile head.

              I'll try making a cutter from drill rod. I'm a little dubious about how to get the center to trim the mandrel correctly.

              Here's a youtube video of installation and shaving....

              http://www.youtube.com/watch?v=g7EUXOA9d78

              Thanks for all the ideas...

              - Bart
              Bart Smaalders
              http://smaalders.net/barts

              Comment


              • #8
                How many rivets do you intend to need? I'd buy the tool if thousands are needed. What material are the rivets made of?

                Back in the day, I made nice round-headed rivets from steel rod using an air tool with a 'bit' that was little more than a hunk of steel with a semi-circle milled into it.

                Comment


                • #9
                  Hi,
                  Had a look for the rivets and found this utube shows the tools in action, seems simple enough
                  http://www.youtube.com/watch?v=g7EUXOA9d78
                  although I think you will need more than the cutter, you will also need to limit the depth of cut.

                  Peter
                  I have tools I don't know how to use!!

                  Comment


                  • #10
                    Brings back memories...

                    I did my apprenticeship in the early 1980's and we used an air driven rivet mill to finish countersunk rivets in the aviation business. That was much simpler though as it was a flat cutter. I have never seen these rivets before, but they look a neat solution. I can't offer any advice on making the cutter though.

                    Stuart

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                    • #11
                      Originally posted by Tony Ennis
                      How many rivets do you intend to need? I'd buy the tool if thousands are needed. What material are the rivets made of?
                      These rivets are used for repair jobs; the first job will require shaving of perhaps 25 aluminum rivets. Over time, as I fix other issues I'll be doing more. Buying the tool makes perfect sense for a commercial shop; that's not me.

                      Thanks -

                      - Bart
                      Bart Smaalders
                      http://smaalders.net/barts

                      Comment


                      • #12
                        Bart,

                        This is the tool that you're trying to copy I guess:

                        http://www.vintagetrailersupply.com/...ctCode=VTS-177

                        (kind of them to show an exploded drawing)

                        The tool reminds me of an aircraft countersink tool with built-in depth stop - this kind of thing:

                        http://www.aircraftspruce.com/catalo...ountersink.php

                        Costs about $38, maybe available on ebay used. They take replaceable countersink cutters - make your own custom cutter out of drill rod, harden it and you're done. Depth settable to 0.001", better than the original!

                        Ian
                        All of the gear, no idea...

                        Comment


                        • #13
                          Try these
                          http://cgi.ebay.co.uk/2-Countersink-...item5885bf838e
                          Nearer you than me!

                          Peter
                          I have tools I don't know how to use!!

                          Comment


                          • #14
                            Originally posted by barts
                            The lathe would be a great approach, but these blind rivets need to be installed before the rivet shaving operation forms the profile head.

                            I'll try making a cutter from drill rod. I'm a little dubious about how to get the center to trim the mandrel correctly.

                            Here's a youtube video of installation and shaving....

                            http://www.youtube.com/watch?v=g7EUXOA9d78

                            Thanks for all the ideas...

                            - Bart
                            Well, with a big four jaw and a really big lathe, just mount the whole job and center on the installed rivets, one by one.

                            Seriously, you didn't say after installation. That does make a wee bit of difference. If you are trying to imitate the first tool Ian showed, it looks to me like the outer bushing forms a guide for the inner cutter. It appears to fit on the outer edge of the rivet head to effect the centering. The inner cutter will have little centering action by itself. The whole thing has bearings and a spring to provide pressure on the cutter. Looks like a nice weekend project.

                            As for the inner cutter, I would look into getting a replacement cutter from the guys who make the tool. This is not a simple drill shaped tool. Study the geometry of an end cutting end mill. To grind one you would probably need a T&C grinder and even then, the concave cutter would be an unusual shape that would be challenging. They are probably made with a special CNC grinder. Since it probably has a special shank for mouting, I would get the cutter itself first and then make the tool around it.

                            An E-Bay search sounds like a really good idea if you have the time to wait until one turns up.
                            Paul A.
                            SE Texas

                            Make it fit.
                            You can't win and there IS a penalty for trying!

                            Comment


                            • #15
                              Hi, I saw a diamond sharpening bit with a hemishperical bottom yesterday, used for sharpening button bits on rock drills. like this:
                              http://www.pora-agentti.fi/images/teroituskupit.jpg
                              It might give you some ideas.

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