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I'm confused (milling feed, speed, and DOC)

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  • I'm confused (milling feed, speed, and DOC)

    I've started an ambitious little project (for me).

    I'm trying to make an ASO (anvil shaped object) out of a new piece of CR 171 crane rail.
    I'm trying to deck the top off flat using a BP clone (3hp) with a 2.5", 4-insert face mill and uncoated Chinese carbide inserts. (It's what I have).

    Like an idiot, before I looked anything up, I was running 660 RPM and made some nice fireworks before I burned up the inserts.

    I've done some searching and found the steel to be an alloy with .65-.75 carbon (100 - 120 sfpm) and came up with 168 RPM.
    The choices on my mill are 135 or 210. I chose 135 because of the origin of my inserts.

    I'm running about 4 IPM but can't for the life of me figure out what my DOC should be.
    I ran a pass at 0.015" DOC and made some very nice golden to purple curls (and NO fireworks) and a decent finish.

    Any pointers would be appreciated. Am I on the right track here???

  • #2
    Originally posted by kyfho View Post
    I've started an ambitious little project (for me).

    I'm trying to make an ASO (anvil shaped object) out of a new piece of CR 171 crane rail.
    I'm trying to deck the top off flat using a BP clone (3hp) with a 2.5", 4-insert face mill and uncoated Chinese carbide inserts. (It's what I have).

    Like an idiot, before I looked anything up, I was running 660 RPM and made some nice fireworks before I burned up the inserts.

    I've done some searching and found the steel to be an alloy with .65-.75 carbon (100 - 120 sfpm) and came up with 168 RPM.
    The choices on my mill are 135 or 210. I chose 135 because of the origin of my inserts.

    I'm running about 4 IPM but can't for the life of me figure out what my DOC should be.
    I ran a pass at 0.015" DOC and made some very nice golden to purple curls (and NO fireworks) and a decent finish.

    Any pointers would be appreciated. Am I on the right track here???
    Golden to purple curls with carbide is fine. With HSS, you want the chips to be silver. Sounds good to me.

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    • #3
      When you have the speed and feed right the DOC will be limited by machine hp and rigidity. Too bad the mills don't have an ammeter so you could know how much of the hp you are actually using. If you stall the motor you can expect to replace all your inserts.

      Comment


      • #4
        If you need to remove a lot of material, I think you can safely double the rpm and DOC. See how it goes and adjust accordingly. Blue chips are OK with carbide inserts. Finishing path- decrease DOC to 0.005-.010".

        P.S. Used rails (esp. railway ones) are usually work hardened on the surface very noticeably, so experiment a bit.
        Last edited by MichaelP; 04-22-2019, 09:01 PM.

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        • #5
          Your question got me to searching the web for speed/feed recommendations for milling. After considerable searching this is the best reference I could find:
          https://www.hannibalcarbide.com/tech...eeds&Feeds.pdf

          Comment


          • #6
            The depth of cut depends on the profile of the insert as well as the HP and rigidity of the mill.

            Most inserts have data sheets available that specify the recommended min and max DOC. Unknown China inserts might not have them. You might benefit from looking at the documentation that comes with the face mill.

            At the very least you want to make sure that the retaining screw or clamp is not hitting the work.
            At the end of the project, there is a profound difference between spare parts and extra parts.

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            • #7
              Originally posted by MichaelP View Post
              P.S. Used rails (esp. railway ones) are usually work hardened on the surface very noticeably, so experiment a bit.
              Fortunately, I got a 6 foot cutoff from a new rail. Advantages of working for a steel mill. I'm using 18 inches for this project. Should have seen me cutting that off with a PortaBand (6" x 6", height and width.

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              • #8
                I can imagine this fun!

                Comment


                • #9
                  For the milling I'd say you're on the right track. You might be able to go faster but for home shop use gold to blue is great in my books.

                  On the "anvil shaped object" I'd suggest you look around more. Crane rail is rather I beam shaped with fairly wide upper and lower faces with a relatively narrow web. So strikes other than on the center are going to result in the flanges and web bending then springing back and you won't get the solid support you are after. By all accounts I've found on YT about "anvil shaped objects" it's more about big solid pieces like big solid rectangles and big solid 4 to 6 inch rounds about a foot or more long sat on end. Basically if it is a solid shape from striking surface to lower support and you can barely lift it or need help to lift it then it's a good option. And for learning apparently mild or lower tensile alloys are fine and actually result in less risk of missed or glancing hammer blows chipping edges out of the surface.

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                  • #10
                    Update: Several passes later, here is where I settled into.
                    210 RPM, 2 IPM feed (to improve finish), and 0.010" DOC.
                    Nice, blue 6&9 chips, and a beautiful, double-cut moiré pattern, mirror finish. (Sorry, no camera here)
                    I have the top at 4" x 18". I'm going to drop the front 6" down another 1/4" before I start forming the horn there.
                    Square up the sides, work on the end under cuts and the feet. Might even consider a hardy hole in the tail.
                    As to the web thickness and possible lack of rigidity, I did think about welding in some 3/4" or 1" plate to beef it up. May wait and see if it's necessary.

                    Anyway, it will be a damn sight better that my current hard, flat surface for that I use bashing things on.... My shop floor.

                    Thanks for all the input guys. If it turns out halfway decent, I'll have to dig up a camera to post some pics.

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