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  • This shape

    I have been thinking about how this shape might tackled with a lathe and milling machine? The flats are above the half way mark. My thoughts so far...

    1. Turn to size on lathe
    2. Mill the two flats
    3. End mill on the top, with the edge at the vertical center, then rotate the part one direction until the end mill edge meets the flat. Give it a quick back and forth.
    4. Repeat #3 mirrored to other side?

    That's the best I could come up with so far.


  • #2
    Let me be the first to say you could do it on a shaper.

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    • #3
      Super easy with a weldment.

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      • #4
        Originally posted by The Artful Bodger View Post
        Let me be the first to say you could do it on a shaper.
        I KNEW that was coming. I tried to head it off at the pass by specifying lathe and mill but alas... here we are.

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        • #5
          If an indexing head, H/V rotary table or spindex is available, it would be no problem to turn a flange on the workpiece and mill the radius detail. Otherwise, use the same procedure, holding the part in a V-block and manually move the part incrementally to machine the radius.

          If two part construction is permissable, silver soldering the shape to a piece of round stock would also work.
          Jim H.

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          • #6
            Look at a rifle bolt head on a typical bolt action rifle; that's the same shape you're trying to cut. I don't know how it's done, but that shape in rifle bolt design has been commonly used for well over a century. These are almost always one piece, BTW.

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            • #7
              You could hold it vertical on a rotary table (if it's not too long) in a V block or chuck. Mill sideways to do one flat, turn the rotary table for the radius and mill sideways for the other flat. By using a small diam. end mill you would have a small radius where the flat meets the curve. This could be filed or milled to get a square inside corner.

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              • #8
                Originally posted by The Artful Bodger View Post
                Let me be the first to say you could do it on a shaper.
                +1

                or use a horizontal mill with cutter like the one on the right



                Paul

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                • #9
                  Your initial idea sound good to me- the only 'extra' you would need is a rotary fixturing device of some kind. An ordinary end mill should do.
                  I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                  • #10
                    Originally posted by SirLesPatterson View Post
                    I KNEW that was coming. I tried to head it off at the pass by specifying lathe and mill but alas... here we are.
                    Well! If you MUST do it the hard way.

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                    • #11
                      Production parts like that might be broached. Fast operation.

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                      • #12
                        Because the tricky bit - the continuation of the axle along the 'head' - is less than half a circle in x-section, it cannot be required for rotatory motion. Hence it need not be an accurate continuation. Even if it slides in a circular channel, I can't see it taking any weight. So I challenge the real need for that shape in the first place. Sealing ? No, not that either.

                        Please provide more details on why that shape is necessary.
                        Richard

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                        • #13
                          OK, we can't deviate from lathe and milling machine. And it has to be one piece.

                          But what about the other specs? Just how round must the extension of the round shaft be between the flats? I mean can it be a two, three, four, etc. flat approximation of round? Somewhere, with enough facets you will get down to +/- 0.001" of a true round. Would that be OK? Would +/- 0.0005" be OK? If not, then what? And if this arc section can be less than round, what rules would apply for transitioning from the round shaft to it?

                          How about a radius between that round section and the flats? Must this corner be completely sharp? Or could there be a 1/16" radius there? Or more?

                          Could this corner be undercut? If so, by how much and on which surface(s), the round or the flats or both? And how big could this undercut be?

                          In my mind, it is all about specs. Just how much fiddle room do you have? And where?
                          Last edited by Paul Alciatore; 10-29-2014, 12:05 AM.
                          Paul A.

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

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                          • #14
                            Here's one way to machine the part.

                            Turn the large diameter in the lathe and mill the flats with a regular straight end mill. Then, use a corner rounding end mill (running along the length of the shaft) to finish cutting the round section of the shaft.

                            See http://kbctools.com/usa/Navigation/N...fm?PDFPage=206

                            Since the flats are not on the center line of the shaft, and the corner rounding end mill is designed to cut a full 90 degree radius, the end of the end mill will need to be ground down.

                            You could also grind a fly cutter to either the exact profile needed or a half profile to cut each side individually.

                            Is this steel or aluminum?

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                            • #15
                              Originally posted by Tom Curlee View Post
                              Turn the large diameter in the lathe and mill the flats with a regular straight end mill.
                              I think I would do this part as Tom says, then single point broach the shaft in the lathe. This is done with the power off, sliding the carriage along the ways by hand and rotating the chuck in small increments as needed. It's time consuming, but not difficult, and works fine for a one-off part. It can leave a pretty good finish with a sharp tool.

                              Here's an example, showing how I've used this method for interrupted threads.



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