the SWARF is alive!

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  • darryl
    Senior Member
    • Jan 2003
    • 14419

    the SWARF is alive!

    Been machining some plastics lately, and the pile behind the lathe is growing, and growing, and growing-

    Anyway that's not exactly what I'm posting about. Yesterday I glued some pvc discs into some abs pipe sections. Today I needed to cut most of the pvc out, leaving basically just a ring behind. Because that would represent most of the material being wasted, and too much time to bore it all away, I decided to hole saw it. Mounted the hole saw in the tailstock and made a press-fit fixture to mount in the chuck to hold the pieces I'm working on.

    As I bring the hole saw into the workpiece the swarf fills the gullets in the teeth very quickly. This means I have to withdraw the hole saw, clean the swarf out of the teeth, and go again- and again, again, etc. Too time consuming. Then I went for a different hole saw, one that I had sharpened and deepened the gullets somewhat. That was faster and I got the job done- still needing 3 cycles of withdrawing the tool and cleaning the gullets out. All is well.

    As I'm working on this I'm reaffirming what I already know- swarf needs a place to escape to. Most of us here know this, but for the sake of the newbies I thought I'd bring it up. There are several reasons to pay attention to this. One is that the swarf can remain in the cut, filling the gap and preventing the cutting tool from continuing to take a proper cut. Another is that it can be dragged along the cut, possibly scratching up the nice finish. Another is that it can wedge between the tool and the cut, again scratching up the surfaces and possibly damaging the cutter, not to mention overheating things. And it can cause tool wander and unexpected over-cutting. If you don't already have a good strategy for dealing with swarf, it's definitely something to think about.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-
  • Doc Nickel
    Senior Member
    • Mar 2003
    • 5784

    #2
    Yep. Just recently I helped some guys put up a wooden shed. They made the wall panels then bolted the four together- somewhat modular, so it could be taken down and moved if need be.

    They'd set the walls together, then run the drill through for a bolt. And he'd run the drill straight. Pushing as hard as he could, and pushing hard until the drill broke through the other side. He'd then have to drag the still spinning drill out- if it stopped, it'd get stuck- after which it'd be smoking.

    I mentioned this to him and he literally looked me in the eye, and with a somewhat challenging tone, said "you got a better way to do it?"

    I introduced him to the concept of "pecking", and the idea that the chips had to actually exit the hole to make room for the drill bit itself. I'm pretty sure I actually saw a little lightbulb flicker on.

    Doc.
    Doc's Machine. (Probably not what you expect.)

    Comment

    • mattthemuppet
      Senior Member
      • Oct 2012
      • 5045

      #3
      how thick are the disks? A trepanning tool would be considerably better if the disks are 1/2in or thinner. If you still need to use a holesaw, drill a few holes on the inside of the holesaw diameter, so that they intersect with the saw kerf. That'll give somewhere for the chips to go so you don't need to keep clearing the teeth/ saw. I did this on a 1in thick steel plate and the holesaw went through in one go, although with lots of cutting oil.

      Comment

      • Mike Amick
        Senior Member
        • Jun 2012
        • 2160

        #4
        I think Doc is saying .. the guy was just using a reg (though, maybe long) drill bit. Just for a bolt.
        John Titor, when are you.

        Comment

        • J Tiers
          Senior Member
          • Jan 2004
          • 44354

          #5
          PVC is a pain. It is low melting material. If you do not pull out the drill fast, the remaining swarf might freeze it in position, welding it in place by fusing with the hole walls. I have had swarf build up faster than I thought, and weld into a solid piece of plastic in the drill flutes.
          CNC machines only go through the motions.

          Ideas expressed may be mine, or from anyone else in the universe.
          Not responsible for clerical errors. Or those made by lay people either.
          Number formats and units may be chosen at random depending on what day it is.
          I reserve the right to use a number system with any integer base without prior notice.
          Generalizations are understood to be "often" true, but not true in every case.

          Comment

          • darryl
            Senior Member
            • Jan 2003
            • 14419

            #6
            For my particular project I needed to minimize the time spent on each piece- there are 50 of these. I tried the trepanning tool first- usually it does a good job and is quick. In this case, because of the way I needed to hold the piece it would have taken longer than hole sawing in the lathe. A hole saw with six teeth would have been best here- three with an outside set and three with an inside set. Much of the problem was swarf removal and the other was holding the piece. As far as drilling clearance holes, that's a good 'trick'. It would have taken longer in this case to do that vs just clearing the tool three times per cut.

            These parts are two piece, one is pvc and the other is abs. In this case the abs is a short section of 2-1/2 inch tubing called cellcore. Interesting material- it has a solid outside and a solid but sort of soft and slick inside surface. Between is a foamed abs core. It's regular DWV pipe. I initially wanted to make my discs out of it as well, so I cut some pipe sections and heated it in the oven so I could make it flat. Then I tried to trepan some discs out of that. Did not go well at all. Then I did the same with pvc pipe and it was a dream to trepan by comparison, but holding in the mill was problematic. I ended up using the table saw to make the 60 odd discs that I needed. Much better result- very round discs and right on size, and much quicker to do besides. I did manage to get covered in pvc 'dust'- and you can't just brush that stuff off.

            Anyway, the final machining operation is facing, and the pvc is cutting like a dream- the abs is cutting but the foamed core is not solid enough to cut well.

            I make a lot of parts from pvc, but unless I have solid abs I won't be making parts from that material.
            Last edited by darryl; 07-11-2016, 07:09 PM.
            I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

            Comment

            • Arcane
              Senior Member
              • Oct 2002
              • 4027

              #7
              Plastic swarf! UGH! I just did a small job for a friend that involved cutting eighteen very short lengths (about 8" long, 6" wide) of composite deck boards down from about 1 1/8" to 5/8" thick. I could clamp three at a time to my mill and use a small face mill to reduce them (very nice finish btw), six passes .250 " deep on one side of the clamp then reclamp and do another six passes all at the top speed of my mill (2720 RPM) and at the maximum table speed travel my powered unit provides. The amount of swarf was terrible! I used a shop vac to suck up as much as possible as I was milling the boards and every 3 pieces filled the vac completely! Afterwards I managed to get another vac full from just what I missed while milling so seven times I filled that vac.
              Last edited by Arcane; 07-11-2016, 07:26 PM.
              Location: Saskatoon, Saskatchewan, Canada

              Comment

              • darryl
                Senior Member
                • Jan 2003
                • 14419

                #8
                As usual, I look at that pile and wonder 'what can I do with that'

                If I was smart I'd gather it all up along with all the other junk and take it to the dumpster-
                I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

                Comment

                • 1-800miner
                  Senior Member
                  • May 2010
                  • 1508

                  #9
                  Melt it down with some beeswax and make machinable wax.

                  Comment

                  • DATo
                    Senior Member
                    • May 2011
                    • 900

                    #10
                    1) Keep it damp

                    2) Use air to blow the chips out

                    Comment

                    • Ian B
                      Senior Member
                      • Dec 2002
                      • 2941

                      #11
                      Don't you just love it when the plastic swarf streaming off your razor-sharp tool does one quick wrap around the work, and then suddenly pulls the huge ball of swarf already in the swarf tray back up, wrapping it (along with the steel & brass swarf that was there already) around the workpiece, thereby causing the razor sharp tool to dig in on what was going to be the finishing cut?

                      Ian
                      All of the gear, no idea...

                      Comment

                      • Paul Alciatore
                        Senior Member
                        • May 2002
                        • 17538

                        #12
                        I think a long time ago another machinist looked at another pile of swarf and asked the same question. And Brillo was invented.



                        Originally posted by darryl View Post
                        As usual, I look at that pile and wonder 'what can I do with that'

                        If I was smart I'd gather it all up along with all the other junk and take it to the dumpster-
                        Paul A.
                        s
                        Golden Triangle, SE Texas

                        And if you look REAL close at an analog signal,
                        You will find that it has discrete steps.

                        Comment

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