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Make a circle out of 2" plate on a CNC?

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  • Make a circle out of 2" plate on a CNC?

    Hey guys, I cut circles on my CNC all the time but now I've got a question. I need to make a D1-8 adapter for a 6" 4-jaw flat back chuck I bought for my big lathe so I figured I'm cut the holes for the pins and set screws as well as rough the ID and OD on my CNC. For thge center hole I figure I'd drill a big hole on the manual mill and then just loop a circular pocket cycle til I cut through the bottom of the plate. For the OD I figured I'd cut a circle say 0.060-0.100 deep and loop it but I'm afraid of breaking the endmill what if I modifiy the circle loop to cut say 0.250 over size then to size before looping down to the next depth? I plan on using a 0.500" carbide long flute endmill, do you think I'll be able to clear the chips enough to keep from breaking the endmill in such a deep slot? Should I run a bolt circle drill cycle a little bigger than the OD first or will the interupted cuts give me trouble? What if the bolt circle was oversize enough that the endmill is always cutting something and just use the holes to clear the chips? I figure I could drill holes and leave only about 1/8" web to support the disk will I do the ID. I have to do two bolt circles anyway for the pins and set screws.

    Anyone have a better idea? What would you do?

    All of the finish work will be done with the adapter attached to the lathe spindle, well except for facing the back of course for than I'll just chuck it in the big 3 jaw. BTW the adapter will be about 9" OD with an ID the size of the chuck.

    ------------------
    -Christian D. Sokolowski

  • #2
    You don't say how thick the plate is, do you?

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    • #3
      ON Adrians site, there is a easy way to cut circles with a torch, then spin it on your lathe to make it perfect.

      I used a torch adapter on my cnc, a long bar to hold the torch over a barrel, you cranked the bed upa nd down to get the height right.

      I almost burned the shop down. I'd suggest something different
      Excuse me, I farted.

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      • #4
        Oops, yep thickness that's the problem, it's 2" plate! Anything less that 1/2-3/4 and I wouldn't worry about it but at 2" thick I'm concerned about chip removal. I'm running two nozzle flood coolant BTW.

        ------------------
        -Christian D. Sokolowski

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        • #5
          "Anyone have a better idea? What would you do?"

          I'd buy some round stock in the correct size.

          Best,

          BW
          ---------------------------------------------------

          http://www.cnccookbook.com/index.htm
          Try G-Wizard Machinist's Calculator for free:
          http://www.cnccookbook.com/CCGWizard.html

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          • #6
            You could nibble away at the top until you are 1" deep and then flip the part over and repeat the process.

            At least your maximum depth will be about 1", which is closer to your 3/4" don't worry zone.

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            • #7
              Other easy fix? buy a backing plate of the correct type. Save the 2" thick for a bender. or??
              Excuse me, I farted.

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              • #8
                Well you could find some one with a water jet cutter and have them rough the OD and ID with a +1/8" - 3/16" tolerance and then finish in on the mill. A simple two circle cutting op would cost about the same as the busted .5 cutter with you supplying the plate.
                Wow... where did the time go. I could of swore I was only out there for an hour.

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                • #9
                  Since it's chip removal you're worried about, couldn't you just hold the shop vacuum near it and have it suck the chips out while it's running?

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                  • #10
                    The guys at the local job shop cut circles like that all the time with their CNC torch rig. Probably about a 20 minute job for them and clean as heck. Just a skim cut to dress it up afterward. You might look for someone to do that for you.
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      Predrill a hole that will be close to the outer edge of your hole that you will be cutting, make it atleast as big as your endmill, this will be your plunge point and pause point. When you program it, write in a M00 right before it goes to plunge to the next Z depth cut, the M00 will pause the machine till you hit cycle start again and allow you too vacuum or blow out the chips with some compressed air. I also like to bolt down the center cut material that you are removing, itkeeps the piece from jumping around when it breaks loose, and prevents you from losing an expensive cutter.


                      Edit: also I wouldnt take more than a .250 per pass on the depth, with a .500 endmill, I might even take less than that.

                      [This message has been edited by mochinist (edited 12-16-2005).]

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                      • #12
                        <font face="Verdana, Arial" size="2">Originally posted by DR:
                        You don't say how thick the plate is, do you?</font>
                        DR...yup,,,he did...the title says 2" plate.
                        Christian...we flame cut these sizes all the time.
                        I just made a set of hubs for an air boat drive. All out of 1 1/2" thick plate.
                        These where flame cut to within (roughly) 1/16" then machined on the lathe.
                        Sounds far simpler than what you are trying to do.
                        Mind you...this is dinasour tech that I speak!
                        Russ

                        I have tools I don't even know I own...

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                        • #13
                          If I was you, I would lay out the I.D. and O.D. on the plate with chalk and rough out each with a hand torch. I would not worry about accuracy because you are merely removing excess material. Get as close as you dare and remember that the cut will probably be tapered one way or the other. Leave yourself enough material to account for this. I would suggest starting the cut with a 1/4" drilled hole to avoid the molten metal spray when you initially pierce. Then use lathe or mill to do the final cuts. If you can, grind the cuts to remove the hardened layer that results from the cutting. An endmill will cut through this layer, but grinding wheels are cheaper. When I cut thick plate with a hand torch, I like to wiggle the torch side-to-side to create a wide kerf so I can see what is going on. Take your time and use a face shield. A tinted face shield (#3) works well for seeing the cut, but sunglasses (like the safety glasses type) will work just as well. Take your time. After the metal changes state to a liquid, give it the cutting oxygen and pretend you are using water from a hose to wash the metal away. Good luck.

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                          • #14
                            I always use a circle cutting jig. You can get very nice circles with these. I've had great results with up to 3" thick plate(Using an LA torch with a #6 tip...8 to 10 acet/50 O2).
                            As was suggested...leave some to cleanup with a grinder of your choice. Once you grind through the scale it will cut easy with end mills etc.
                            I have tools I don't even know I own...

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                            • #15
                              Sorry, no torches involved on this project, too hard on Carbide endmills. I could easily chuck this piece in my 4-jaw and cut it as well but that's not the point. For a D1-8 backing I need 6 1" holes with a setscrew hole right next to them. I want to drill those holes as well as cut the center hole and outside on the same setup on the CNC so when I mount the backing plate to the lathe I won't have much work to do to finish it up. I like mochinist's idea best for this. And M00 stop is easy and can be incorporated into a loop with ease. Heck I'm gonna have three tool stops in there anyway to spot drill and drill the different hole sizes and then to an endmill for the ID and OD. Also if this works well I'm going to want to make two more backing plates and a face plate. It's like when I made sets of soft jaws for the 3-jaw as well as the CNC's twin vises, if I need more I just load stock and walk away or do other things. Soft jaws for the vises are cut entirely in one pass and then after installation I have a program to step the tops inline with the X-axis.

                              I suppose I should have specified I only want to do it on the CNC and I'm looking more for ideas for the best way to accomplish that. The M00 will work nicely and with enough coolant a lot of the chips will flow out of the stop hole anyway.

                              ------------------
                              -Christian D. Sokolowski

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