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New to metal lathe concepts....what or how were these made

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  • New to metal lathe concepts....what or how were these made

    Hello , I'm new to this metal world of machining ...I'm a average DIY'er , wood lathe's , saws , drill presses yada yada....I stumble on a piece I want to make and it made out of metal



    I watch some videos and look around at forums and I see cylinders being made routinely. But I haven't seen a jig or device that would make those half circles in metal... I'm assuming that was / can be done on a lathe...but looking at some of the amazing videos of the cnc setups I see out there I'm not sure...Has anyone seen what can make them ?

    thanks

  • #2
    A ball nose end mill is an easy way to make them, depending on the size you need and the material. You would then need to polish out the tooling marks.

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    • #3
      Excellent....I'll research them. Do these ball nose end mills go up to 3'' ?

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      • #4
        Welcome aboard! Those parts can indeed be made on a manual lathe. As mentioned, a ball nose end mill in the tailstock will work for smaller radii; larger concave radii can be done with certain types of radius attachments, aka ball turners. In the photo below, one side of the insert is for convex radii, the other for concave.

        -Brian

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        • #5
          Here is the kind of "device" used to do radii of various pieces on a lathe. For small radii "Internal" (like the pictures) I came up with a way to make a cutter do complete hemispheres.
          http://home.earthlink.net/~lhartswic...diusturner.jpg
          If you want additional info let me know, I've got lots of pictures of the kind of Balls I've made with the Holdridge shown above.
          ...lew...

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          • #6
            Awesome !! these exactly the answers I was looking for...it can be done...and there is something that I can get to do it...Even with that I know a learning curve will come with this process...Now its time to pick out my first metal lathe...

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            • #7
              Originally posted by innerg View Post
              Excellent....I'll research them. Do these ball nose end mills go up to 3'' ?
              possibly, but if you could afford it, you'd need one f''er of big tailstock chuck lol.

              if those are 3", dollars to donuts they were done with a radius attachment.....there are commercial ones but they frequently appear as diy projects.

              I believe you can also do so with a fly and rotary table held at an angle....but thats the mill not lathe

              What are they?
              .

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              • #8
                lol .. These things are what they are calling a bath bomb mold...They come in various shapes / sizes.. ( 2.25'' -2.50'' being the most popular sizes ) I've even seen them made from some plastic material...maybe pvc...

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                • #9
                  If it's just a bath bomb, the mould could be cast first then finished in the lathe, radius turner or form tools, if form tools probably a couple of tools to reduce the cutting face to a manageable length.
                  Mark

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                  • #10
                    A ball mill cutter restricts you to a given size.

                    But if you look up "ball turning tool" and look at images you'll see a lot of versions which can also turn concave recesses like this to any sort of radius. Here is only one of the various setups made by hobby machinists.

                    At the fourth and fifth pictures down on THIS PAGE you will see a ball turning attachment that uses an HSS cutter. The fifth picture shows it turning a portion of a concave cut. Used in this mode on the end of a piece of round stock it would cut the sort of spherical depression you are looking at for a radius up to the maximum it can reach and stay stable.
                    Chilliwack BC, Canada

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                    • #11
                      2 inch ball end mills go 300 on msc don't wanna know what a custom 3 inch one would cost . If you wanted to make one on a manual tho I would use a radius Turner but you probrarly could grind the radius on a hss tool bit as a form tool and do all the math to figure out how far in a how deep at each pass that would be the cheapest option

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                      • #12
                        Originally posted by Mcgyver View Post
                        I believe you can also do so with a fly and rotary table held at an angle
                        Tom Lipton's book covers this technique. He shows how to use it to cut internal and external spheres. Pages 174 to 179 in "Metalworking - Doing It Better". I believe his "Sink or Swim" book has mostly the same content, so it's probably in there too. He shows how to visualize the path of the cutting tool by putting an o-ring on the sphere. The o-ring remains in full contact with the surface.

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                        • #13
                          Originally posted by tbsrokks05 View Post
                          2 inch ball end mills go 300 on msc don't wanna know what a custom 3 inch one would cost . If you wanted to make one on a manual tho I would use a radius Turner but you probrarly could grind the radius on a hss tool bit as a form tool and do all the math to figure out how far in a how deep at each pass that would be the cheapest option
                          3" ball end mill is peanuts compared to the milling machine that is capable to take a cut with it!

                          ---
                          And if making on a lathe you need quite sturdy ball/concave turning attachment if you want to get it done in reasonable time. Better be plus 12" swing lathe also.

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                          • #14
                            Forget about doing large hemispheres like the OP shows with a ball end mill in a lathe tailstock. That would take an incredibly large, rigid machine to overcome the chatter.

                            Also, most ball turners won't do a complete female hemispheres.

                            The ones shown could have been done on a CNC lathe with a boring bar. Or, in the pre-CNC days with a tracer lathe.

                            They could also be done with a CNC vertical mill using a small diameter ball end mill to contour the interior profile. There were also some pre-CNC die making mills that could do them.

                            You could tediously do these in a homeshop manual lathe using a boring bar with multiple depth cuts calculated following the interior contour. Time consuming and need to carefully set a micrometer type depth stop for each cut.

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                            • #15
                              Originally posted by DR View Post
                              You could tediously do these in a homeshop manual lathe using a boring bar with multiple depth cuts calculated following the interior contour. Time consuming and need to carefully set a micrometer type depth stop for each cut.
                              thats a good point. and imo its really not that tedious. I've not done it for a concave curve, but its so easy and works so well for outside radius I've never bothered to make a radius cutter. You'd have to use smaller steps for this as you are not going to be able to round things off with a file....but its very doable with no special equipment
                              .

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