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Educate me on knurling, please

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  • Educate me on knurling, please

    I want to knurl something on my Craftex lathe. I have been doing a little research, and it seems that the best type of knurling tool is a "pinch" type knurler. The power feed screw on my lathe doesn't work. (Thats a whole other story). Do knurlers self feed or do they require a power feed screw? Any help would be appreciated. I don't want to build a knurling tool, I just want to know enough about them to buy the right thing.---Brian
    Brian Rupnow

  • #2
    Scissors or pinch type knurlers usually have rollers above and below the work. When they are positioned properly on the centerline of the lathe, they should be neutral as far as X-Y forces on them but this is an unstable position. In actual practice, some force is needed to keep them in position. The cheaper import tools also have some play in them and this allows odd forces to come into play. Tighten all adjustments as much as possible. Also, if the knurl you are making is longer than the rollers are wide, the tool will need to be moved across the work and this takes force. These forces must be controlled by mounting the tool in a tool post and using the X-Y feeds.

    When you say your power feed screw does not work, I assume you mean just that, and the manual feeds do work. If they didn’t, the lathe would be useless until they are repaired. Knurling is done with manual feeds, I do it all the time. I’m not even sure if I would want to use power feed. I open my scissors type tool wider than the work and position it as close to the center line as possible. I also position it at one end of the knurl I want to produce. Add lots of cutting fluid and then start to tighten the scissors. If the knurl is longer, I use the carriage handwheel to move it back and forth across the knurled area, adding more cutting fluid as needed. The scissors is tightened a bit after each pass over the length of the knurl until the full depth is reached. Then you can remove the tool by any of several ways; loosening the scissors nut, backing off on the cross feed, or running it off the right end if that is possible.

    Get one, chuck up a bit of scrap, and try it. You’ll like it.
    Paul A.
    SE Texas

    Make it fit.
    You can't win and there is a penalty for trying!

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    • #3
      Thanks Paul---where do I find such a wondrous device, and approx how much do they cost.---Brian
      Brian Rupnow

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      • #4
        Here are a couple....

        http://www.victornet.com/cgi-bin/vic...86%2C313%2C317

        roughly $40->$50 for import...

        - Bart
        Bart Smaalders
        http://smaalders.net/barts

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        • #5
          I use power feeds for knurling all the time, but as mentioned, I'm sure manual works.

          But don't use cutting fluid. Knurling displaces metal and needs lubricant, not cutting fluid.

          And, in my experience, you want to plunge quickly to target depth, don't try to sneak up on it. Easing in is asking for a double track. Might want to practice on a scrap piece of like diameter, or better yet, on an area you are going to turn off after knurling. Find out what depth yields a nice knurl, notice where the hand wheel handle is at that depth (so you don't have to look at the dials), and when ready, just crank directly to that position/depth.

          But, "how" to knurl seems a bit of a personal thing, and the specifics of how to feed it in varies quite a lot by person, often accompanied with an almost religious fervor regarding the correctness of that particular method. Lots has been written here on the matter, so a search can yield lots of extra info...
          Last edited by BadDog; 04-26-2009, 03:43 PM.
          Russ
          Master Floor Sweeper

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          • #6
            I use the pinch knurling tool, but I found a way that works better for me than running it on center.

            I move the tool over center and tighten the grip until the knurls just touch the work. Then I back away, and tighten the tool down just a little farther than the depth of the knurls - I just guess at the depth.

            Then, I run the tool into the work, again until the knurls just touch. Here I'm checking to make sure each roll touches at the same time so they will cut evenly. If needed, I loosen the toolpost and let the rolls find center or raise and lower the tool manually, then tighten up, and recheck.

            Now, I'm set to go. I turn on the lathe and run the tool into the work. Since the rolls are very close to pinching the work, there's very little force needed as I press inward.

            For me, this system works much more easily than leaning on the knurling tool knob with a cheater bar to get enough pressure quickly. I can get to full depth quickly and have a spare hand to pour the cutting fluid.
            Cheers,

            Frank Ford
            HomeShopTech

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            • #7
              uh oh a knurling thread

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              • #8
                Originally posted by Paul Alciatore
                The cheaper import tools also have some play in them and this allows odd forces to come into play. Tighten all adjustments as much as possible.
                You guys have got me thinking - I need to fix up my import scissors knurler. I think many of these import things have to be thought of as assembled parts kit rather than something that'll do a nice job right out of the box.

                When I use this knurler as it currently is, I do notice some off axis slop, particularly when I apply infeed pressure (could be sloppy lathe,) and also when starting to feed.

                I just took my knurler apart, and the main scissor surfaces where the two halves rotate on each other has a very rough finish. I think I'm going to try mounting it in the 4 jaw and face the surfaces so they have more surface contact (which will also help align the left/right of the top/bottom knurls.)

                The bolt shaft/pin that these rotate on proves a super sloppy fit, and it's only 1/2" diameter. While I've got it in the 4 jaw, I just might bore out the pivot hole to 3/4" or 1" diameter, and get a tight fit on a new shaft/bolt (with extra large head) to increase off axis stability. That should help keep them straighter when there is left/right force on them, without locking it down so tight that it can't pivot to find the center.

                One thing that always drives me nuts is that the only way that the knurler's square shank will fit in the toolholder is if the knurls are way far away from the toolblock - 3.75". In other words, the pivot bolt for the scissors is about where the normal tool bit edge would be, so I have to move the cross slide waaay back, and sometimes adjust the compound so it can get far away enough from the part.

                I'm thinking I might make a custom QCTP tool holder for the knurler. Basically a solid block with a tapped hole that the scissors bolt/pivot shaft will screw into. The hole would be located towards the back (operator side) of the toolholder, so I could switch holders from turning to knurling without having to move the cross slide a mile.

                -Matt

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                • #9
                  Originally posted by mochinist
                  uh oh a knurling thread
                  I gather that for some reason this is an unpopular subject. I posted a knurling question last week, and despite something like 100 views didn't get one response.

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                  • #10
                    Originally posted by x39
                    I gather that for some reason this is an unpopular subject. I posted a knurling question last week, and despite something like 100 views didn't get one response.
                    It kinda like the bearing threads, you have a whole board full of self proclaimed experts and each has a way it must be done. They're usually entertaining


                    what was your question?

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                    • #11
                      What if the diameter of the knurler isn't a divisor of the diameter of the work piece? Does this not make a mess?

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                      • #12
                        file two teeth off..........

                        .
                        .

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



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                        • #13
                          Originally posted by x39
                          I gather that for some reason this is an unpopular subject. I posted a knurling question last week, and despite something like 100 views didn't get one response.
                          No I'd say it's a very popular subject. I guess about one every week.
                          :-)
                          ...lew...

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                          • #14
                            (oooooops)

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                            • #15
                              Originally posted by mochinist
                              It kinda like the bearing threads, you have a whole board full of self proclaimed experts and each has a way it must be done. They're usually entertaining


                              what was your question?
                              Well, in a nutshell I have a quantity (80 pcs.) of 5/8" dia. tp304 ss rods that need knurling over a length of 18". I was asking whether anyone had experience with the Dorian straddle type knurling tools. I ultimately wound up purchasing a Stafford Special Tools unit from MSC, primarily due to the fact that 21 tpi knurling wheels were available in cobalt with a convex form, which I couldn't find for the Dorian tool. I just got the tool on Friday night and haven't had the opportunity to use it yet.

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