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  • nurling

    Can any-one tell me the set up specs, procedure and so-on for nurling on a late.

    thanks Ron

    ------------------

  • #2
    Yes, I usually do my “nurlingâ€‌ pretty late. It gets cut off if I do it early.

    Seriously, there are two general types of knurling tools. The straight tool which usually has two side-by-side (top/bottom) rollers and the scissors style which has two rollers on opposing arms that are tightened together.

    With the straight style tool,
    1. Mount the tool in the tool post, facing the work.
    2. Apply a generous amount of cutting fluid.
    3. Feed in hard enough to produce the desired knurl.
    4. You can move the carriage left/right to produce a wider knurl.
    5. Apply additional cutting fluid as needed.

    With the scissors style tool,
    1. Mount the tool in the tool post, with one arm/roller on each side of the work.
    2. Apply a generous amount of cutting fluid.
    3. Tighten the arms to produce the desired knurl.
    4. You can move the carriage left/right to produce a wider knurl.
    5. Apply additional cutting fluid as needed.

    With either style of tool, there is debate as to the need for calculating the OD of the work based on the pitch of the knurl. Many will insist that this is absolutely necessary, reasoning that the pattern produced by the knurling tool is very much like the teeth on a gear. That they are a precise size and must be precisely spaced for proper effect. Others say that this is not really necessary, just use enough pressure and a fast in-feed to produce a proper knurl.

    You should plunge the tool in to near full depth as fast as possible. Or with the scissors style tool, tighten them together fairly quickly. This helps to prevent a double pattern.

    I have observed that one of two things can happen when knurling. You either get teeth of the desired size or you get exactly half sized teeth. This proves to me that they are not precisely sized by the tool and there is a self-adjusting action in the process. It is probably good to be close to the proper size, based on the pitch of the roller, but not absolutely necessary. What I would avoid is being too close to the half tooth size. Thus, if your knurl has 15 teeth per inch, avoid a size that would work out to 29 or 31 teeth per inch.

    The knurling tool works by displacing metal. So your OD before knurling should be about half way between the peaks and valleys of the desired knurl. This is approximate because metal can also flow sideways in the process. Also, it is good for a straight knurl but a diamond knurl will need a slightly smaller starting OD because more metal will be displaced from the valleys. This is only important if you need to have good control of the OD after knurling. Most parts don’t so the exact OD can be ignored.

    Last thing. Keep the rollers clean of chips. Yes, chips will form in the process. They flake off some alloys. I use a brass wire brush to clean the rollers while knurling. Any chips on the rollers will make impressions in the pattern, causing it to look rough.

    Picture of me knurling: cutting oil in one hand, brush in the second, third hand is tightening the knurling tool and the fourth is traversing the carriage back and forth the width of the knurl. I definitely have to put the coffee cup down for this one. Fun.

    Paul A.
    Paul A.
    SE Texas

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

    Comment


    • #3
      One caution to go along with Paul's second hand wielding the chip-cleaning brush: Be careful not to let the brush (or anything else) get caught up in the knurls. They won't let go, and will happily walk through anything...or break, or stall.
      ----------
      Try to make a living, not a killing. -- Utah Phillips
      Don't believe everything you know. -- Bumper sticker
      Everybody is ignorant, only on different subjects. -- Will Rogers
      There are lots of people who mistake their imagination for their memory. - Josh Billings
      Law of Logical Argument - Anything is possible if you don't know what you are talking about.
      Don't own anything you have to feed or paint. - Hood River Blackie

      Comment


      • #4
        Thanks Paul, I just completed building me a sissors style knurling tool and was wondering the exact use of it. Now I know!
        Thanks Mel
        _____________________________________________

        I would rather have tools that I never use, than not have a tool I need.
        Oregon Coast

        Comment


        • #5
          In addition to the other posts:

          Set the knurls square to, and reasonably close to the centerline of the work. Use a low RPM and an aggressive feed rate.

          Here are some "not to do's" when knurling:

          1. DO NOT disengage the automatic feed while knurling until the knurl is COMPLETE. Disengaging the feed will produce a damaged area in the knurl pattern. Leave the feed engaged until desireable results are obtained. You may need to run the knurl through several cycles to get the results you desire. This is done by stopping the lathe, changing the direction of the rotation of the leadscrew and re-starting the lathe. You may have to run the knurl through several cycles to get the results you desire. At each cycle, add more in-feed or clamping pressure. When the knurl is complete, stop the lathe and back off the in-feed or clamping pressure. Then you can disengage the power feed.

          2. Do not back off on the in-feed or clamping pressure. Doing so will also produce a damaged area in the knurl pattern.

          3. Do not run off the end of the part, as the knurl will not pick up the "track" from the previous pass.

          The "straight" or self centering knurling tool does put quite a strain on the cross feed screw. Whereas the scissors type put no strain on the crossfeed screw.



          [This message has been edited by ERBenoit (edited 11-29-2005).]
          Paying Attention Is Not That Expensive.

          Comment


          • #6
            Make the knueled diameter an even "pitch" diameter of the knurl. Mike the knurl and count the teeth. Divide the knurl diameter by the number of teeth and machine the work so its an even multiple of this number.

            If you don't you'll get multiple knurls and other problems.

            That aggressive first stab of the knurling tool is good advice. Metals have limited ductility. If you try to make it deform and flow too many times it will fatigue. Go for full depth at a single pass if you can.

            Comment


            • #7
              Paul: Thanks for all the help. I guess you noticed I can't spell. Whats funny is my wife was a teacher and she told me the wrong spelling for knurling. Go figure. Kindest regards Ron

              <font face="Verdana, Arial" size="2">Originally posted by SGW:
              One caution to go along with Paul's second hand wielding the chip-cleaning brush: Be careful not to let the brush (or anything else) get caught up in the knurls. They won't let go, and will happily walk through anything...or break, or stall.</font>

              Comment


              • #8
                <font face="Verdana, Arial" size="2">Originally posted by Forrest Addy:
                Make the knueled diameter an even "pitch" diameter of the knurl. Mike the knurl and count the teeth. Divide the knurl diameter by the number of teeth and machine the work so its an even multiple of this number.

                If you don't you'll get multiple knurls and other problems.

                </font>
                Here we go again,
                What diameter the OD, the root diameter or the theoretical pitch diameter.
                They are all different and on a fine to medium knurl will encompass 2,3 or even 4 teeth.

                If you don't believe me read this thread

                http://bbs.homeshopmachinist.net//Fo...ML/009237.html

                Sir John.
                So what is right ?

                .

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



                Comment


                • #9
                  Sir John, You are,as usual.

                  ------------------
                  The tame Wolf !

                  Comment


                  • #10
                    Hmmmm....

                    I do knurling on a number of 200-500 part repeat runs. A couple are aluminum, which is undoubtedly one of the most difficult materials I know of to knurl.

                    We pay no atention to the diameters, knurl pitches, etc. Also, other than a small squirt of coolant to lube the knurl axles it's done dry.

                    After intital trial runs to get the setup right, 99+% of the parts are perfect.

                    All the production knurling we do is in the CNC's with opposed wheel knurling tools. Rpm a bit less than cutting speed, single pass, very high traverse rate, and get the tool off the part, never allow it to dwell on the part.

                    One job the knurled diameter has to be held to close tolerance (don't ask). Cut the beginning diameter to size. A few trial runs while adjusting knurling tool, then a final light skim cut over the knurled area to bring it to size within .001"+/-.

                    Comment


                    • #11
                      here we go again, exactly what I thought when I saw this thread. Ron, there are a lot of skilled people here who's work and opinions I value, yet they seem to be split down the middle on how to knurl. what finally pushed over the fence to the JS 'have it it' school was his point that unlike a cut gear, the pitch dia circle changes as the knurl progresses...this agrees with my experience.

                      Forrest I’m trying to imagine forming a knurl in one pass – must be a very fine knurl in soft material in a big lathe? I’ve a 13x36 and always found knurling over many passes pretty demanding – I would not want to put much more force on the crossfeed screw. Are you using a scissor type knurl to accomplish this, or can you give some more insight?



                      [This message has been edited by Mcgyver (edited 11-29-2005).]
                      .

                      Comment


                      • #12
                        Thanks for your reply. I am using a 2 cutter straight tool on a 16x36 engine lath.
                        <font face="Verdana, Arial" size="2">Originally posted by Mcgyver:
                        here we go again, exactly what I thought when I saw this thread. Ron, there are a lot of skilled people here who's work and opinions I value, yet they seem to be split down the middle on how to knurl. what finally pushed over the fence to the JS 'have it it' school was his point that unlike a cut gear, the pitch dia circle changes as the knurl progresses...this agrees with my experience.

                        Forrest I’m trying to imagine forming a knurl in one pass – must be a very fine knurl in soft material in a big lathe? I’ve a 13x36 and always found knurling over many passes pretty demanding – I would not want to put much more force on the crossfeed screw. Are you using a scissor type knurl to accomplish this, or can you give some more insight?

                        [This message has been edited by Mcgyver (edited 11-29-2005).]
                        </font>

                        Comment


                        • #13
                          I thought sure and Sir J would mention his "cut knurler" with a pic of the deep knurl on what looks like a piece of Morris exhaust pipe....

                          That sure looks like a good idea to me..... I hate forcing in the knurl, and I tend to do straight knurls, so scissors setups are no help.

                          With straight knurls, it DOES seem to make a difference if the diameter is right...... I have been unable to get it to work without splitting the points, and then turned down a bit and it went on like butter.

                          However, with a fine knurl, there is a "right" diameter every few thou, so I can see it being relatively non-critical.... It just hasn't been for me. Not my thing....

                          But then I am not running some 5 ton Springfield behemoth, and I can't just ram the knurl in to depth instantly.
                          1601

                          Keep eye on ball.
                          Hashim Khan

                          Comment


                          • #14
                            Usually i feed her a big bottle of cheap wine before any serious nurling activities.

                            Comment


                            • #15
                              As I said, there IS debate. I am sure the size of your lathe is a factor in determining the best technique. As is the alloy you are knurling. Do some practice pieces first and see how things work for you.

                              As for knurling dry, try it if you like, but I found that cutting fluid helps a lot in the appearance of the knurl. I use Tap-Magic and Tap-Magic for Aluminum. All the usual disclaimers. I am sure others will work as well or perhaps even better.

                              Paul A.
                              Paul A.
                              SE Texas

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

                              Comment

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