Announcement

Collapse
No announcement yet.

cutting sharp knurls

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

  • cutting sharp knurls

    Many people report having "aha!" moments, where they receive enlightenment. I seem to have "duh!" moments, where I become aware of the blindingly obvious.

    For years I've been jealous the the guys who turn beautiful sharp diamond knurls on a lathe. I've schemed, and figured the pitch diameter of the knurl and turned the workpiece down to some multiple of it, and tried different knurlers, and all the usual tricks. Sometimes it works, sometimes I get dull or splintery knurls.

    I was just looking at a picture of a part made from a particularly hard to work alloy, with beautiful sharp knurling and thought, "you know, you could do that with a threading tool making right and left hand passes at a low thread pitch."

    Well, duh...

    So it only took me a few decades to discover a trick everyone else probably picked up fifteen minutes after they walked up to a lathe. I'm slow, but I get there eventually...

  • #2
    Welcome, I am a charter member of the "D'uh" group as well.

    My thinking is I will have to live a much longer life just to pick up some of the basic/most obvious stuff

    I have learned to create "threads" by leaving some headstock adjustments really loose so the spindle moves back and forth...it was my first clue to a better finish as well as a reminder about keeping attentive.

    Comment


    • #3
      You may be in for another "duh!" moment when you figure out how coarse the thread must be and the number of passes needed

      I had my own "duh!" moment when I managed to get a really well formed knurl and went to use it -- so painful to use that I eventually lightly filed it to remove the sharpness.

      John

      Comment


      • #4
        There are alternatives to knurls.
        If the part is a decent diameter then make oversize, drill a ring of holes and turn the ring off so only about 1/3 of the hole is left, deburr and you have a nice usable part that can easily be gripped.

        This screw,



        Not mine, I saved it a while ago but can't give credit as I never made a note, possibly Frank Ford ? looks like his work.

        Is generated by annular grooves on the lathe followed by horizontal grooves on a 4th axis but very precise.
        .

        Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



        Comment


        • #5
          If you like straight knurls you can get a very crisp look by cutting them with an ordinary end mill and a rotary table. The result looks like below.



          I posted this a few weeks ago so rather than repeating it here, see
          http://bbs.homeshopmachinist.net/sho...ghlight=rotary Post 35 for details.
          Bill

          Comment


          • #6
            Get an opposed wheel knurling tool. Perfect knurls 99.9% of the time with no calculations for blank size, etc.

            The opposed wheel types come as the common "scissor" type or the more rigid type used in screw machines.

            Fast feed onto the work and faster off. Ideally, no more than a couple revolutions of the work. You don't want to repeatedly run over the knurl area.

            Comment


            • #7
              I can highly recomend a cut knurling tool . close up is of the cap on the spout, about 1/2" dia brass



              .

              Comment


              • #8
                Originally posted by Mcgyver
                I can highly recomend a cut knurling tool . close up is of the cap on the spout, about 1/2" dia brass

                .................................................. .................................................. .

                Yes, some people have good luck with them. It's too slow for our production parts.

                The reason I wouldn't recommend one is the "mush" of metal chips they create which can be pushed back into the knurled area. This can be a real problem with aluminum when the parts are color anodized. The little flecks of material come off in the process leaving a spotty part.

                Any type of knurling in aluminum can be a problem though. Years ago I had a customer's aluminum part calling for a coarse diamond knurl, then black anodize. Almost impossible, unless the parts are thoroughly wire brushed prior to anodizing. I did a lot of research on the problem, wondering how high production parts are processed. Talking with anodizers and finding they were well aware of the aluminum problem. I was surprised to find very few commercial aluminum parts with a diamond knurl. Most that I found had straight knurls which appeared to have been extruded that way.

                Comment


                • #9
                  Originally posted by DR
                  Yes, some people have good luck with them. It's too slow for our production parts.
                  .

                  how so? what other knurling tool runs at full speed and cuts in a single pass?
                  .

                  Comment


                  • #10
                    I wondered about that comment.
                    I have one of the Quick knurling tools and the local Aerospace company often borrow it and they only run high grade production jobs.

                    Knowing their operator he'll run it at 2,500 revs which is as fast as his CNC lathes go because he runs everything at that speed, just alters feeds to suit.
                    .

                    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                    Comment


                    • #11
                      John - Thanks for the grand compliment - not mine, but I can dream. . .

                      Originally posted by John Stevenson


                      Not mine, I saved it a while ago but can't give credit as I never made a note, possibly Frank Ford ? looks like his work.

                      Is generated by annular grooves on the lathe followed by horizontal grooves on a 4th axis but very precise.
                      Cheers,

                      Frank Ford
                      HomeShopTech

                      Comment


                      • #12
                        OK Frank, can't think who else it could have been and I do like to give credit where it's due.

                        Sure you don't want to 'adopt' it ?

                        It does wind me up to see others work on web sites with no accreditation and thinly veiled text to make the reader think it's all the OP's work. There are certain whole web sites out there earning money based on others toils but give nothing back.
                        .

                        Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                        Comment


                        • #13
                          Originally posted by John Stevenson
                          OK Frank, can't think who else it could have been and I do like to give credit where it's due.

                          It could just tell Frank didn't have a finger in that ....but it looks good enough to be his work
                          .

                          Comment


                          • #14
                            Originally posted by Mcgyver
                            how so? what other knurling tool runs at full speed and cuts in a single pass?
                            My favorite and nost used knurl tool is a B&S scissor type with round shank mount, It runs at fast spindle speed in the CNC lathe, maybe 2,000 rpm. It comes in from the side at around .030" ipr to part center, no dwell, rapid off part. Fast setup like any scissor type.

                            I have a couple cut type knurlers. Haven't tried them inyears. I do recall setup taking a bit of time. Plus I believe they have to run with coolant. Most knurling is done dry, except we program a short burst of coolant aimed at the knurl wheels to lubricate the roller pins just prior to the knurling operation.

                            I see lots of interest on the forum in cut knutlers. All I can say is if they work for you, good. For me, I'll stick with the forming knurlers.

                            On edit: I forgot to mention high quality cut knurlers are quite expensive aren't they? IMHO, that's another reason to avoid them.
                            .
                            Last edited by DR; 05-07-2012, 12:51 AM.

                            Comment


                            • #15
                              Actualy McGyver wrote up an awesome design and build for a cut knurler a couple of years ago in the HSM magazine.

                              Pete

                              Comment

                              Working...
                              X