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  • Problem with ATPK inserts.

    I'd heard good things about ATPK inserts and thought to give them a try. I bought from Sharrs an APTK tool holder, clained to be a 90* holder for shoulders. Well, I tried cutting a shoulder and it wasn't 90* and the vertical edge seemed to curve. What happened? Bad inserts? Bad tool holder? Or just a bad idea? My 3 1/2" Chi-com holder with cheapo triangular inserts does nice 90* shoulders and a fine job of facing.

  • #2
    It will be the holder. I've never seen an insert with bad geometry, but .. I do buy name brand inserts. My APTK insert/facemill definitely cut a 90 shoulder.
    Last edited by lakeside53; 02-28-2010, 11:07 PM.

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    • #3
      Well, looks like I have a nice 1" indexable drill with ATPK inserts.

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      • #4
        Send it back. I am sure they will send another.

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        • #5
          Do not send it back. You will just get the same thing back.
          What is the radius on the inserts? 90 deg cutters aren't exactly 90 deg, they just cut an approximately square corner. This is due to some confluence of the the insert geometry and how the cutter tilts the inserts back to try to give a true helical cutting edge. What's the brand of the inserts? I don't trust Shars to know what they are doing anyway. Maybe a real company like Kennametal or Iscar or Seco who makes both inserts and cutters can get it right. At some point, remind me to side mill with my Iscar tool and Iscar inserts. Maybe there is some good Israeli synergy...

          edit:
          Now that I think about it, one insert can not get the helix right for all cutter diameters.
          Last edited by beanbag; 03-01-2010, 04:46 AM.

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          • #6
            Rakes progress

            Originally posted by JTToner
            I'd heard good things about ATPK inserts and thought to give them a try. I bought from Sharrs an APTK tool holder, clained to be a 90* holder for shoulders. Well, I tried cutting a shoulder and it wasn't 90* and the vertical edge seemed to curve. What happened? Bad inserts? Bad tool holder? Or just a bad idea? My 3 1/2" Chi-com holder with cheapo triangular inserts does nice 90* shoulders and a fine job of facing.
            Can you post a pic and a link please.

            For a straight edged cutter to cut a vertical face the cutter edge must be truly vertical - ie it must be accurately parallel the cutter holder axis - like this:
            https://www.machineryhouse.com.au/Pr...stockCode=M503

            https://www.machineryhouse.com.au/Pr...stockCode=M510

            https://www.machineryhouse.com.au/Pr...stockCode=M528

            These sort of cutters have both "vertical" (zero) "rake" as well as "tilted" (usually positive)rake.

            If the edge is "tilted" (and straight) the "vertical" cut surface will be "curved". To eliminate that problem the cutting edge needs to be in the form of a spiral as is the case with a standard HSS or TC spiral-toothed end milling cutter.

            For proof of this, put a straight edge (any - your call) against a cylinder such that it is parallel to the cylinder axis. The straight edge will show no gap between it and the cylinder.

            Now tilt the straight edge against the cylinder and only one part of the straight edge will contact the cylinder. As the straight edge gets further away from the cylinder the gap between the cylinder and the straight edge will widen.

            The straight edge represents the cutting edge on the insert/s.

            I suspect that the inserts and the cutter-holder are OK but that the rake is positive to reduce the cutting load.

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            • #7
              Jttoner,
              How deep of a cut did you take on your finish pass?
              Maybe some deflection?

              Mike

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              • #8
                Is the problem that the shoulder is not square, or that it's not cutting well, or both?
                There are many styles of APKT inserts. Some have a broad radii which leaves a really nice surface finish. Is this what you have?



                Is this the facemill you bought? It looks crudely machined, but it should still work OK, and that's the flat-wiper style APKT insert you want for a square shoulder:



                Interestingly, the 4" Shars APKT facemill looks nicely made -- this is clearly from a different supplier:

                http://www.shars.com/products/view/7...ll_APKT_Insert
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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                • #9
                  I think the OP is slightly confused

                  That endmill will cut *TO* a square shoulder and leave a square, assumeing you take multiple shallow passes endmilling adjusting the z a little deeper each time.

                  That endmill will not cut *A* square shoulder in a single deep pass side milling.

                  Indexable endmills really are not great for side milling, unless you get one of those 10+ insert looks like a corncob dealies, else you just end up with an interrupted cut from hell. (Without helix, side milling is basicly an interrupted cut where all the work is done in 1/20th the rotation)
                  Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                  • #10
                    Originally posted by Black_Moons

                    Indexable endmills really are not great for side milling, unless you get one of those 10+ insert looks like a corncob dealies, else you just end up with an interrupted cut from hell. (Without helix, side milling is basicly an interrupted cut where all the work is done in 1/20th the rotation)
                    As they say on the interweb:

                    x2

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                    • #11
                      Ok, that explains the problem, will only do 90* when incrementally adjusting the Z axis. Surprisingly, I've had excellent results with good (not Enco) triangular inserts when cutting 90* to a shoulder. I've had to do this with a variety of metals, eg., A2, 4140, 303, and even 6061. No problems side milling with them either, but a boatload of problems side milling with HSS, whether conventional or climb milling. As a rule, with the indexable face mill and triangular inserts (Either TT or TPx, I'd have to check which as I have both, but don't recall which are in the face mill), I run at 1450 rpm using a 3 1/2" dia. tool. I may be doing it all wrong, but it seems to work. Anyway, like I said before, I can use the 1" ATPK as an indexable drill. I didn't check to see if it will plunge, probably not, but if I begin with a 1/4" drill, that shouldn't be an issue. Obviously, I'm no machinist, but I do enjoy metal work.
                      Johnny

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                      • #12
                        Well, with carbide you can get away with insane speeds, but if you go to fast with HSS it will be instantly dulled behond use.

                        You can do light side milling with non helixed inserts, but it tends to produce a lot of hammering action if much deeper then 0.03" per pass in mild steel. At least on my machine. Maybe it can still do deeper, but I pucker when I hear RATATATATA and my whole 1000lb machine shakes back and forth half an inch.
                        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                        • #13
                          Originally posted by JTToner
                          Anyway, like I said before, I can use the 1" ATPK as an indexable drill. I didn't check to see if it will plunge, probably not, but if I begin with a 1/4" drill, that shouldn't be an issue. Obviously, I'm no machinist, but I do enjoy metal work.
                          Johnny
                          Don't do it. That's not what it's for

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                          • #14
                            Beanbag, you're correct, but the thing is utterly useless for anything else. BTW, the tool holder is Sharrs 404-1863 and the insert is of Austrian origin, no name or number available.

                            Johnny

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