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  • A neat machining trick

    When I designed the hexagon shaped manifolds for my twin steam engine, I wanted them to have "domed" ends, so I designed them that way. Now it's true,--You can do some things on the computer that are almost impossible to do in "real life". The hex rods were drilled out full length to 1/4" inside diameter, then a brass plug silver soldered into each end. I have tried shaping a dome on the end of stock with a file, but was never terribly successful. Then I remembered the 1/2" hand held belt sander that I seldom use. It removes a lot of stock very quickly. I ran the lathe at about 200 rpm and with the running belt sander in hand I shaped the dome "freehand". It went very quickly, and gave excellent results. It worked so well that I considered it worth posting about.---Brian

    Brian Rupnow
    Design engineer
    Barrie, Ontario, Canada

  • #2
    Originally posted by brian Rupnow View Post
    When I designed the hexagon shaped manifolds for my twin steam engine, I wanted them to have "domed" ends, so I designed them that way. Now it's true,--You can do some things on the computer that are almost impossible to do in "real life".
    A lathe form tool (one with a radius in this case) does it easily.
    Mike
    WI/IL border, USA

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    • #3
      MichaelP--I'm sure you are right. If I had a hundred of them to make, I would do exactly what you suggest. For two, this worked quite well.
      Brian Rupnow
      Design engineer
      Barrie, Ontario, Canada

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      • #4
        A round over (corner rounding) mill works as a form tool. I use one with a 1/8" radius all the time to put a rounded end on .250 alignment pins.

        A ball turner would have also worked, and probably have given one of the best results.

        Obviously the finger sander and the lathe also worked.

        The right tool for the job is the one you have access to AND that produces an acceptable result.
        *** I always wanted a welding stinger that looked like the north end of a south bound chicken. Often my welds look like somebody pointed the wrong end of a chicken at the joint and squeezed until something came out. Might as well look the part.

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        • #5
          I usually pick one of my hand ground form tools I made.
          I detest grinding or sanding on my good lathe..
          Quicker to make a form tool from 1/4 inch square HSS for that job... than cleaning up the lathe after a sanding operation..almost.
          Every form radius tool I made has been used for many applications.

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          • #6
            Originally posted by brian Rupnow View Post
            I ran the lathe at about 200 rpm and with the running belt sander in hand I shaped the dome "freehand".
            Brian - if you have a belt grinder, a similar method with small parts is to chuck them in a cordless drill and spin them against the belt grinder. Essentially the same as what you did, other than moving the "lathe" (drill) instead of the grinder. I've been using that method for years before I had a lathe; it works great and is very quick.

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            • #7
              I have given up totally on cordless drills, because when the batteries die, they are just too expensive to replace. All of my drills now have a cord and plug in, which is perfectly okay by me. I do have a monster stationary belt sander, and your method would have worked fine, but since I was working on the lathe at the time and had the handheld belt sander nearby, that is what I used.
              Brian Rupnow
              Design engineer
              Barrie, Ontario, Canada

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              • #8
                Many ways of skinning the cat. Thanks for showing yours.

                How do you like that little belt sander? I've had one on my amazon wishlist for a while now, but havn't pulled the trigger on it. I have an air belt sander like that, but hate running the compressor all the time. I'm concerned that might be a little light duty compared to what I'm used to, but how did it make out on the brass?

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                • #9
                  Originally posted by 754 View Post
                  I usually pick one of my hand ground form tools I made.
                  I detest grinding or sanding on my good lathe..
                  Quicker to make a form tool from 1/4 inch square HSS for that job... than cleaning up the lathe after a sanding operation..almost.
                  Every form radius tool I made has been used for many applications.
                  Ugh---what he said, so succinctly.
                  sarge41

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                  • #10
                    I would have chucked that hex up in my 3-jaw and whipped out the ball turner. Set the radius to the high point and done in five minutes.

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                    • #11
                      Originally posted by CCWKen View Post
                      I would have chucked that hex up in my 3-jaw and whipped out the ball turner. Set the radius to the high point and done in five minutes.
                      If I had more than one to do I'd have done the same. :-)
                      ...lew...

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                      • #12
                        There's one on each end. That makes two.

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                        • #13
                          I like that little electric belt sander a lot. I too thought of buying a pneumatic one, but firing up the compressor and unrolling hose all over the place is just a pain in the arse. I'm not sure if they still make these, but I certainly like it. I had a Steve Bedair ball turner but never used it so I gave it away. As far as sanding on my lathe goes--I sand on it, I machine cast iron on it, I use a toolpost grinder on it.--If it dies, I'll buy another one.
                          Brian Rupnow
                          Design engineer
                          Barrie, Ontario, Canada

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                          • #14
                            I don't mind sanding or grinding in the lathe but I do take precautions. I've got a small towel with one side marked "UP" that I use for keeping grinding dust off the ways and make sure I don't flip the towel to the dirty side down by accident. With that I don't mind doing some abrasive work.

                            Brian, I think it's a case of we CAN do it with a file. But we tend to get lazy and stop before our vision is fully realized. And our spherical end isn't so spherical. Using the power belt just allows us to achieve what our mind sees far more easily and makes touching things up effortless so we do them.

                            Just a couple of days ago I did a classic shaped teardrop handle for a crank for my shaper. I roughed it out with a cutter then attacked it with a bastard file. I could see that this was going to take nearly forever. So I stopped to mask off the bed with the towel and get out the battery angle grinder with the flap disc. It made the job so much easier to reach what my mind's eye saw. I seriously think I would have stopped early if I had stuck to files.

                            HERE'S TO POWER TOOLS ! ! ! !
                            Chilliwack BC, Canada

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                            • #15
                              Originally posted by BCRider View Post
                              I don't mind sanding or grinding in the lathe but I do take precautions. D
                              sanding is about 1000x worse than grind imo. Grind only puts out a meaningful quantity of grit when dressing whereas sanding just sheds abrasive material. When using emery, pot magnets and paper towels are how I protect the lathe. imo rags/towels are more dangerous, if a thread gets caught it'll pull you in.

                              A partially domed end is such a nice way to finish ends, I keep form tool in a QCTP holder.
                              in Toronto Ontario - where are you?

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