Announcement

Collapse
No announcement yet.

When parting on the lathe, why?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • When parting on the lathe, why?

    Hi Group,

    When I'm parting something on the lathe I often get pieces like this with the darndest tab on the face of the part when there is a hole in the middle. What do I need to learn from you to remedy this, or is this something that I need to just deal with it !

    It's not all the way around like I haven't finished cutting. I have the tool on center and when it's a solid piece there is no tip left at all on either piece when done parting, so I think I have the height set correctly. The tool I'm using is on a AXA parting tool QCTP holder with a 1/8" HSS parting blade nice and sharp, in my opinion.

    Click image for larger version  Name:	IMG_20200217_133333277.jpg Views:	0 Size:	712.5 KB ID:	1858423

    Look forward to discussion on this topic.

    TX
    Mr fixit for the family
    Chris
    Last edited by Mr Fixit; 02-28-2020, 01:16 AM.

  • #2
    Easing up just before it breaks results in a thinner crust, that will come off easier. You can use the numbers on your cross slide to figure where that is.Or I use sidecutters as it usually gets chamfered anyway.

    Comment


    • #3
      I always chamfer that away as well.

      Comment


      • #4
        Even with a sharp edge and even with an angle on the end to try to cut off and leave the tag on the stock I often got those.

        A clue as to why it happens can be seen when we look into the ID and see the material swaging a ring of material inwards. I think the metal fatigues and breaks rather than cuts that last few thou. A roughly 20° angle on the end with the tip towards the work helps as does easing up on the last little bit while still keeping a chip rolling. But it still doesn't solve it all the time.
        Chilliwack BC, Canada

        Comment


        • #5
          Yes, slowing your feed rate as you break through will help.
          I just need one more tool,just one!

          Comment


          • #6
            Grind a slight skew on the end of the parting tool, so you break through on the 'part' side first, which should then come off clean. Feed in a bit more to remove the flash from the stock end.
            'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

            Comment


            • #7
              Originally posted by Richard P Wilson View Post
              Grind a slight skew on the end of the parting tool, so you break through on the 'part' side first, which should then come off clean. Feed in a bit more to remove the flash from the stock end.
              I use Seco insert tooling for all my parting operations. They make inserts which are straight on the face or angled slightly to
              left or right. Using a tool with the leading edge on the RH side will leave you with a clean cut on the finished part. Running
              faster also helps. I do most of my parting between 600 and 1100 RPM...
              Keith
              __________________________
              Just one project too many--that's what finally got him...

              Comment


              • #8
                My pieces are concave or convex because of the flex of the cut-off tool. Any suggestions for a good cut off tool?

                Comment


                • #9
                  make the cut in two steps.

                  Comment


                  • #10
                    the angle skew on the parting tool does help with the burr tab, but then it wants to run a bias (crooked cut) to the weak side.
                    try a thinner parting tool too, I have never run one as wide as your 1/8

                    Joe Pie has a good video on youtube about parting
                    ​​​​​​https://www.youtube.com/watch?v=5LtYzjR1JuM&t=945s

                    Comment


                    • #11
                      I have a 9"SB which is a bit 'flexible' as lathes go. I'm not using insert parting tools but blade type in the AXA holder.
                      I've found these tools cut steel like butter. They're not very spendy so give them a shot.
                      https://www.icscuttingtools.com/catalog/page_316.pdf

                      Comment


                      • #12
                        Originally posted by Richard P Wilson View Post
                        Grind a slight skew on the end of the parting tool, so you break through on the 'part' side first, which should then come off clean. Feed in a bit more to remove the flash from the stock end.
                        That works really well, but on deeper parts it does pull the tool a bit. While I'm a big believer is HSS having a major role in the home shop, for parting, I'm now exclusively inserts. Main reason is the geometry; they get such a nice side clearance molding in that eliminates binding and makes parting a breeze.

                        as for the big burr, I break the worst of it off with some fine side cutting pliers then hit it with a deburring tool or countersink in a drill chuck (hand held)
                        Last edited by Mcgyver; 02-28-2020, 08:20 AM.
                        .

                        Comment


                        • #13
                          Originally posted by I make chips View Post
                          I have a 9"SB which is a bit 'flexible' as lathes go. I'm not using insert parting tools but blade type in the AXA holder.
                          I've found these tools cut steel like butter. They're not very spendy so give them a shot.
                          https://www.icscuttingtools.com/catalog/page_316.pdf
                          you must have a lot of money.

                          Comment


                          • #14
                            Having tear out material like that is not uncommon. It's got to give out some where when it gets to the point where the thin wall of material can no longer support the part it lets go.
                            There is always going to be some sort of tab left. It varies with material being parted. You might play around with the speeds and feeds and get a bit more uniform on the tear out but I don't think you could ever part something with out having to do some clean up on either of the two separated surfaces.

                            JL...............

                            Comment


                            • #15
                              Parting inserts are available in left, neutral and right handed. The handed ones will leave a smaller burr on the side of your choice, but have the shortcomings of being unable to cut exactly straight, as the tip angle puts a sideways force into the equation. It is easy to grind an HSS blade also with a slight end angle of about 3 degrees to get a similar effect. I agree with the slowing of the feed rate just before cutting through to the hole, the burr will be thinner and easier to remove.

                              Comment

                              Working...
                              X