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facing on lathe versus mill?

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  • facing on lathe versus mill?

    In the description of how Sir John built his QCTP he says to mount the Tool block in the four jaw chuck and face all the sides. What is the advantage to do it on the lathe vs. mill. I would think it would be faster and easier to do it on a mill. Or what am I missing? Sir John are you awake yet?
    How to become a millionaire: Start out with 10 million and take up machining as a hobby!

  • #2
    It was probably just convenient to do that way. I don't know of any advantage, assuming that you have both a lathe and a mill, and that the mill is not otherwise occupied.

    Dan
    At the end of the project, there is a profound difference between spare parts and extra parts.

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    • #3
      Probably quicker and easier as on the mill there will be no top clamping to hold it against the bed whilst on the lathe the tool will push towards the chuck.
      My 2p
      Peter
      I have tools I don't know how to use!!

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      • #4
        That does not make sense to me. The work would be in a vise and the face mill pushing it to the bottom of the vise. The only difference I see is the work is turning on a lathe. On a mill the tool is turning.
        How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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        • #5
          According to his reply of 9/12/2010 in this thread:

          http://www.model-engineer.co.uk/foru...s.asp?th=46016

          — John states — "The design was probably done around 1980 and I think it was published in ME in about '85 or '87".

          At that time a high proportion of UK model engineers still didn't have standalone milling machines. So, he described a construction technique that was accessible to all readers with a lathe rather than just those with a milling machine.

          Joe

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          • #6
            Unless you have a large face mill of fly cut it in one go on the mill, the surface finish will look better faced in the lathe.

            Dave

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            • #7
              DavidJ wins the prize!

              Now that David makes sense to me! I am making a 100mm square tool block and I have a 160mm face mill with ten inserts. I can face it in one pass. Ok just wanted to know.
              How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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              • #8
                the advange on the mill would be if your fly cutter on your mill is to small and you want a flawless pass and all at once then the lathe would be the advantage so it could be done, the disadvantage is if your cut is not percisly the same debth you will not have a perfect square so you need to pay closer attention when squaring up all the sides on the lathe, but that s just my 2 cents...

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                • #9
                  The lathe should face the whole thing in one cut, AND should face it flat or slightly concave.....

                  With the mill, you have to be certain the mill is "trammed" correctly, and that multiple cuts will meet exactly.... if you can't do it in one go. otherwise there may be flatness and convexity issues

                  Bottom line is that the lathe can do the job quickly and in a known good manner, if in reasonable condition. (not that the mill can't.... but there are more "if"s )
                  1601

                  Keep eye on ball.
                  Hashim Khan

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                  • #10
                    Lathe HSS or inserts are generally cheaper and/or can be resharpen in a home shop, endmills not so much. It's cheaper.
                    The shortest distance between two points is a circle of infinite diameter.

                    Bluewater Model Engineering Society at https://sites.google.com/site/bluewatermes/

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                    • #11
                      The one time I tried to face off on a lathe, the thing pounded so much that I quit and used the mill.

                      Perhaps the piece was too long.

                      To overcome the cost of end mills vs HSS I made this unit which I already posted once on this board.

                      Vitَria, Brazil

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                      • #12
                        With the lathe, won't the surface quality get progressively worse as the cutter approaches the chuck center axis? When facing large disks, I had a hard time getting a good finish this way. What I eventually did is doubling the speed of the lathe on the fly half way... But still, there was a little stub left at the very center and I needed to file it off

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                        • #13
                          If your tool is sharp and you're are right on center, there will not be a nub. And you are right; you have to take into account feed rates with large stock.
                          Tom - Spotsylvania, VA

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                          • #14
                            of you look in the "Book of all Books" you will see in that in theory turning can produce a much better finish in the microfarreds(sp?) scale i think a mill says 63 and a lathe can go right down to even 16 i think.I could be wrong on the exact figures but i know according to the book a lathe is capable of a better finish.

                            I idealy the setup on a mill is easier but it takes a great skill to properly grind a bit for a single point cutter and far too little people have that skill (not saying john cant) to get a really nice finish and i mean far better than any endmill or carbide tipped cutter can produce.

                            my guess was because it was fun to set up and do on the lathe, and it theoretically should look better.

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