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  • Corse spline cutting

    My buddy showed up at my shop today with a 60 year old transmission input shaft for an old Massey Harris tractor. I found this thread and decided to try to duplicate the idea in the second post: clicky

    Here is a quote from the thread, hopefully including the pictures I copied.

    Originally posted by Bguns
    I used a hand ground bit in a 1 in bar (kind of fly cutter style)held in collet in my Cincinnati 2MI horizontal mill ( would work just as well with a vertical). used dividing head with tailstock, ran fairly slow feed and speed to keep vibration down. Came out like a factory job, fit clutch splines exactly like original. Spend the time grinding the single point cutter to exactly match existing good part of spline, be sure to have tip relief and side relief and make chips. I made about 4 passes to full depth of spline and did not have to touch up bit once...

    Here are some pictures of the tool holder and bit that I made.





    My buddy ground the HSS lathe bit to match the existing splines. He put more relief on it that I would have thought was needed, but neither of us have ever ground our own cutter, so we were going off descriptions, and playing it by ear. I don't know if it makes any difference, but I was using this in my vertical mill, I don't own a horizontal mill.

    Anyhow, the problem was this, the cutter seemed to be knocking, no serious vibration, but it wasn't making chips. For whatever reason, it was just pounding the work until the tip of the cutter wore/broke off. We built the damaged section of the shaft up with weld and then turned it down on the lathe with carbide inserts. I don't know if the problem was due to the weld being too hard, or if it is cutter geometry. We are going to have another go at re-grinding the cutter tomorrow. Any advice?

    Thanks,
    Jason

  • #2
    I think you know the answer . My guess is the weld to hard. But befour you start again Rough out the slot with a small end mill the mount the fly cutter tool and rotate it by hand and check for clearance after regrinding your tool bit.you may slow the RPM down if the shaft is tough.I think you are on the right track just take it easy to start you can always speed up after you see what is happening.
    Every Mans Work Is A Portrait of Him Self
    http://sites.google.com/site/machinistsite/TWO-BUDDIES
    http://s178.photobucket.com/user/lan...?sort=3&page=1

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    • #3
      A single-point tool like that isn't going to be very smooth cutting. It is just like doing an interrupted cut on the lathe where the tool slams in, springs back when it cuts free and then repeats the process. You'll want to take light cuts.

      You may also want to try taking a file to the weld to see how hard it is. You may need to try a carbide tool (which will probably be more prone to chipping) or anneal the welded area to soften it. As lane says, anything you can do to remove excess metal with an EM (and you may want to use a carbide EM if the shaft is hard) first will be a big help.

      cheers,
      Michael

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      • #4
        It was welded with ER70-S6, which should not be much harder than mild steel, but who knows what the 60 year old base metal was and whether it would have effected the weld area hardness much or at all.

        I just had another thought though, is it possible that the point of the cutter is to far from the center of the holder, causing it to enter the work at to shallow of an angle? It seems that maybe closer to the axis of the holder may make it slap less. I have done interrupted cuts on the lathe before, this thing literally sounded like a wood pecker...

        My original plan was to make a holder that took an insert to do this, but I didn't have any inserts close enough to the right shape/angle and nothing to try to grind them with so I decided to try the HSS.

        Thanks for the advice so far.
        Jason

        Comment


        • #5
          Jason, the farther the tip is from the center the more flex you've got in the assembly. I think that making it all as short as you possibly can would be a good plan.

          Did you make sure that you didn't get the cutter tip positioned so that it is entering the cut too high or low (like having a lathe tool too far above or below center)?

          cheers,
          Michael

          Comment


          • #6
            Originally posted by jacampb2
            It was welded with ER70-S6, which should not be much harder than mild steel,
            Agreed on the filler: ER70S6 is just mild steel wire with extra silicon as flux for dirty steel -- it shouldn't be able to get very hard. Did you weld the entire spline in one shot, or did you do it in sections, and let it cool in between?

            I can't tell from your picture, but did you grind a top rake angle into the form-cutter, so the bit isn't hitting the work flat?
            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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            • #7
              I've never used that wire myself, but it's a high carbon (0.07) and manganese and silicon alloy. The carbon content alone suggests that it would harden if cooled quickly.

              Maybe John S. could suggest a wire that is easily machined, since he seems to often use MIG to build up damaged shafts?

              I've learned the "hard" way that welds almost always have to be annealed before machining, when using 7018 or even the humble 6011.

              Typical Wire Chemistry
              C 0.07
              Si 0.80
              Mn 1.45

              Typical Mechanical Properties (As Welded)
              Yield Strength, psi 73,000
              Tensile Strength, psi 90,000

              By comparison, mild steel is 36,000 - 40,000 psi.
              Last edited by MTNGUN; 11-12-2007, 10:09 PM.

              Comment


              • #8
                ER70 is .07% carbon -- that's considered mild steel (0.05–0.29% carbon content).

                Medium carbon is 0.30–0.59%, and high carbon is 0.6–0.99%.

                Originally posted by MNTN
                Yield Strength, psi 73,000
                That's the "70" in ER70, or 7018 stick electrodes: the yield strength of the weld. ER60, or 6061 stick electrodes, have 60 K Psi yield strength.
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

                Comment


                • #9
                  Originally posted by lazlo
                  Agreed on the filler: ER70S6 is just mild steel wire with extra silicon as flux for dirty steel -- it shouldn't be able to get very hard. Did you weld the entire spline in one shot, or did you do it in sections, and let it cool in between?

                  I can't tell from your picture, but did you grind a top rake angle into the form-cutter, so the bit isn't hitting the work flat?
                  My buddy did the welding while I was turning the fly/spline cutter, so I am not sure how much he welded at one time. There was top rake, however, one thing I did not account for was where the tool would be in relation to center. The hole for the bit is drilled on center radially through the holder. So, this does put the cutting edge ahead of the center line of the tool holder. There was still enough relief ground that there would be no rubbing of the heel, but perhaps we need to regrind with the cutting edge on the center line, or as close as possible. It did cut a very light cut for about an inch before it just started making noise. I suspect part of the problem is the massive amount of relief he put on the heel, it probably weakened the cutting edge a lot, but I really think that there is a geometry problem here as well. I just don't have the experience to know what it is. If anyone could give better ideas with more pictures/angles of the tool, I can shoot some more.

                  As for the welding filler, if I am not mistaken, the tensile strength of the filler or steel does not have a whole lot to do with it's hardness. It was not cooled quickly, I know that for sure, we didn't want to take a chance warping the shaft. It could need annealed, and if that is the case we will try it tomorrow.

                  Thanks again for all of the help so far.
                  Jason

                  Comment


                  • #10
                    Maybe I will try the cutter on a chunk of CRS just to give a test of if it will cut something that hasn't gotten hot... I will hit the shaft with a file next time I take the dog out and let you all know the outcome. I have filed my welds numerous times though, so I kind of think this is an unlikely culprit.

                    Comment


                    • #11
                      I've done some shaft repair in the past on projects like yours, I would be willing to bet that your shaft is made of something between 1045 and 1080. The rod mixed with the parent metal can be quite hard because the shaft acts like a heat sink and rapidly pulls the heat from the just welded area, just like a quench. Try a file and see how hard it is. If it is hard you will have to anneal it before machining. If it isn't hard then you will have to check the geometry of your cutter. Make sure that the top of your cutter is on the centerline of the fly cutter or just slightly below center. If it is to far above center then it takes a lot of clearance to make it cut thus making the edge weak, and then it won't cut well.

                      -brian
                      -brian

                      Hello, my name is brian and I'm a toolaholic.

                      Comment


                      • #12
                        Having done the original pictures, I will go a little further in

                        Use only enough back rake as needed, too much will really weaken the poor cutter, which is getting the $$$$ pounded out of it ...

                        My job was into the original non welded Model A Ford Input shaft ,which was pretty hard, I would say around 40 Rockwell C or higher.

                        You could make a larger diameter tool holder with hole offset and less tool stickout. Flex is your enemy.

                        Tighten unused table locks..

                        Try to start at about 1/4 of total depth, Some steels will work harden if not aggressive enough on feed (tough with single tooth cutter tho)

                        The file test listed above should be done (If you can't cut weld with a file, HSS won't either...

                        Annealing and a reheat treat may be required (or even that might not be possible, due to whatever happened during welding).

                        Another messy option, is to dress a thin grinding wheel to proper form and grind the bugger...

                        I also used a 5500 lb beast with 50 taper tooling still sounded like hell.. I was amazed edge held up for whole job...
                        Last edited by Bguns; 11-13-2007, 04:41 AM.

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                        • #13
                          Well, I worked on this again today, all I can say is I have got to be doing something seriously wrong with the fly cutter. I reground the cutter, moved it way in, put the cutting edge on center, and it cut better, but once I got fairly deep in the spline, it started to rub, and with the cutting edge ground so far down into the bit I didn't have a lot of room to grind more relief. If I ground more, then I snapped the tip off. I was also never able to take much of a pass with it, it is just plain ground wrong. I will educate myself further in my spare time though.

                          Here are pics of the cutter when I gave up on it:





                          I ended up making this out of a HSS end mill. This was my original idea, until I say Bguns post. I tapered the EM to fit the spline and then I cut tapered flats 180° opposite each other. Put a bit of radius on the tip and shallow relief in the center of the "spade" on either flat. I was kind of surprised that it cut at all, I am sure it is no where near correct geometry, but I was out of ideas. It actually cut quicker than the fly cutter. Made chips and a passable spline. I had to re-sharpen it several times, and was about out of EM by the time I got the 10th spline done, but it did a satisfactory job, and not a real terrible finish either.



                          Anyhow, here's the results. I have to clean up the OD of the splines a bit. I let my buddy try his hand at turning the weld down, and he got it a bit cocked up, all in all, I am anxious to see if the clutch disc fits after all of this work.



                          Later,
                          Jason

                          Comment


                          • #14
                            splines repair

                            I do the weld repair of shafts ALOT! 1 st rule is turn the shaft down before welding so you later machine JUST THE WELD! The weld bond to parent metal section is what gets VERY hard! Even in mild steel or scrap iron.

                            mark61

                            Comment


                            • #15
                              Thanks Mark -- that's a good tip. Sir John mentioned that he turns the shaft down by 1/16" before he MIG welds it, but I think that was to keep the weld from delaminating from the parent material (i.e., so you're not milling past the weld line).

                              By the way Jason, it's too late now, but it occurred to me that you might want to try the form cutter on a piece of mild steel to make sure it's cutting well before you go for broke with the weldement.

                              In any event, nice job on the repair!

                              Cheers,

                              Robert
                              "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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