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south bend 13" and reaming tapered holes

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  • south bend 13" and reaming tapered holes

    This is the motor drive unit assembly for my south bend 13". I'm finally getting a chance to get it up and running and complete. Today, I spent about 2 hours tearing it down and the rest of the day doing battle with this taper pin holding the pulley on.

    I admit, this tapered pin has got the best of me. Regardless of how much beating and heating and cussing at it, she's stuck. I had one aircraft length drill bit and it's only 3/16. Got it through drilled to that and my plan is to pick up a 5/16 drill tomorrow and hopefully finish it off.

    Having never reamed a tapered hole for a pin before, I am looking for old wisdom on drill size and taper for this repair. So the hole, according to plan D here, will be 5/16 in diameter and approximately 2" from end to end.

    Any rule of thumb or tricks/non-tricks (for franz) as to the taper and pin size I should seek for the greatest chance of success?

    ...or if anyone that has one of these laying around they'd like to get out of their way....part not available, of course.
    Attached Files

  • #2
    Hmmm. I have no idea but I would try cussing at it some more and see if that helps

    Miller Trailblazer 325 efi
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    • #3
      Brings some beers over, we'll gang up on it.


      • #4
        I know you said you heated it, beat it...cursed to no avail, but I'd take a small gas welding tip, heat it, the pin, red hot almost melting and let it cool. Then I'd weld a washer to the top with enough lip for leverage.Once cooled,wedge and tap into the underside with a cold chisel and hopefully it will pop out. Could it be the problem that the pin has been torque bent in the hole? Nudging the pully back a hair might be a solution? I'm sure however as a man of many talents you'll figure it out.


        • #5
          I got a feeling my last wife ran that machine and it suffered the same fate as the hubs on her Wheel horse.

          5 bucks says the machine was kicked from forward to reverse enough times to shift the pulley and put a step into the key.

          Since you got far enough down the road to begin drilling, 10 bucks says you don't strike oil, even in Texas. What you DON'T want to strike is shaft. If the pully has shifted sufficiently you can drill into ****** shaft, and that ain't good.
          Sure wish you would have brought it by sooner.

          Drill in like a dentist, bit diameter no larger than the diameter of the pin at intersection. Grind or chisel small diameter end of pin flush with the hub opposite and tap gently on that end with a small punch and hammer to look for motion inside the large end hole. If the pulley has shifted you won't see the big end of the pin moving. You get lucky you'll see the full diameter of the pin. You see shifted, or nothing, it becomes a different ball game.

          Worst case, use drills with flat faces to remove all the pin from the hub down to the level of the shaft. Then drill & tap the pulley face unless you can work a bearing puller type device behind the pulley for a safe pull that won't break the pulley. Install pulling device, 401 parker hammer into a pulling yolk would be my first choice. You can always hit it harder, but often don't need to.

          Pull the horn off a Co2 bottle so you can concentrate Co2 onto the shaft. Rig a deep collar onto the end of the shaft to retain Co2/Dry ice for the pull.
          Heat the hub to around 300° with the torch of your choice, and put the Co2 to the shaft to instachill shaft only. Apply pulling force, preferably air hammer derived.

          Have catching system in place before applying force.
          My personal preference is one of the cushions beer trucks drop barrels onto, but a old tire with plywood on top will work if the job is low budget.

          If that don't remove the pulley you got a slight problem. AttiTood can come down to help, but you could probably build a puller for less than Fastenall or Greyhoud wants for the ride.


          • #6
            From Tarry99....up under a different heading...

            Tapered Pin huh?.........seems like a strange place for a tapered pin.......normally see a key-way and set screws in that application. As others have said if you can weld a nut to it perhaps a slide hammer and some heat will make it move..........sometimes even heat and penetrating oil or even bees wax works to break it loose. Is the cavity or pin open to the opposite side?..........tapered pins were used in some old lathes as shear pins and sometimes made from aluminum to break........rather than find a replacement a std shear pin will do the job.......just ream the hole to the final go no-go dimension and send it home.


            • #7
              This task has been attempted on this part before, just not by me. One end of the pin was mushroomed slightly and the other had been ground down. The opposite end of the shaft, where the jam bits are supposed to be is also damaged by hammer blows, but I'll address that later. I had to polish the edge of the pulley and etch the metal to identify the pin completely. Then I went a heatin and beatin. I center punched it and even went after it with an air hammer. I think you guys might be right, she's got a little step in there. I'm glad you guys brought that up, I didn't consider that.

              Getting straight down to it is a problem. The edges of the wheel stick out some, so you can't really get straight on it, even with a long punch or a jobber length drill bit.

              I know for sure the bit I used has passed dead center through the pin. I started drilling on the small end side and passed it right through the center of the fat end. I left it overnight with soak of ballistol on the off change it'll give up.

              I don't really have a small brazing tip, but at this point, I won't mind putting a little extra heat to it anyway.


              • #8
                Tarry....this machine has been taper pin heaven. It would appear that in 1945, south bend favored the taper pin method of holding everything together. Every single taper pin, besides this one, came out with no problem.

                I'm not against modifying any part of this to make it chooch, but I'd prefer to return it it's original-ish assembly in the off chance that I ever get rid of it, there won't be any surprises for someone needing to preform a repair.

                Plus it's a good learn opportunity. I was inspecting some charts last night regarding taper pin sizes and holes and such. I'm still a little fuzzy on some of the details, but I believe a #5 taper pin will work. So for the sake of buying more stuff, I have it figured to get the aircraft length bits, tapered reamers and pins for a 5 and a 6 (in case I screw up) set up from McMaster-Carr for around $150 freedom bucks.

                But, that's plan Q, R or S...don't remember. I have a couple other things to try. Just don't know if I'll be able to get to them today. I just don't want to spend a week trying this and that when I could've spent the money and for it done in 20 minutes. You know what I mean though, preaching the choir on down time here.


                • #9
                  I would guess you must first identify the type of taper? Morse being the most common , but there are many more out there.........that pin could be made on the lathe.....and then heat treated.........have you reached out to the South Bend forum folks for assistance on removal and replacement parts?


                  • #10
                    I called south bend, now grizzly, and they pretty much suck. I haven't looked into another forum. Honestly, I don't want to get involved in another forum.

                    I don't think this needs a shear pin. This assembly hangs under the head stock and the weight of it with the motor is what puts tension on the drive pulley in the counter drive and head stock. Probably why it was a taper pin to begin with.

                    I can get any ole drive pulley with the same inside shank diameter and overall OD, but that'll end up being more work than repairing this one I think since there is no key way. I've seen where guys will drill between the pulley and shaft and make a key way. That'll be plan W.


                    • #11
                      Its like a #1 taper pin. I have a reamer. Check mc for sizes..Bob
                      Bob Wright


                      • #12
                        Looking at the charts, I had thought a #5 was good, but after looking at some bits out in the shop I think it's too big.

                        I don't know what is on the now, but it's about
                        .310 thou at the big end and .240 thou at the small end. It has a 3/16" hole going through it now, so about .180 thou.

                        The 5/16" hole I was going to drill through it will be too big I think.

                        I'm gonna end up with a piece of friggin rebar sticking through this thing.

                        I'll look into that #1 taper, Bob, thanks. Unfortunately mcmaster-Carr doesn't sell onesies and twosies of these pins. I have to buy a pack of 10, 25 or 50. But once I'm done, I'll have plenty to share with you fellers in need of such a creature.


                        • #13
                          Can't wait to get into the rest of this....
                          Attached Files


                          • #14
                            This guy reassembled an identical assembly. Mine has the original motor though. A frame 203, which I don't think you can get anymore.



                            • #15
                              1945 production date on the machine brings to mind that the machine may be in the collection of parts era. War production contracts were getting cancelled in 44, and the machine tool industry had inventories of parts for machines not yet assembled. A lot of those parts were built into 'we can make it work' machines sold to customers on waiting lists since 42.

                              I had the privilige of running a 1942 machine that spent 43,44, 45 & 46 dwelling in its crate inside a skid shed that the roof had to be removed for access to get the machines out. Many shops with War contracts took advantage of unknowing wartime clerks to obtain machines they could use as trade goods during the war. The world that machine was built in bore little resemblance to the one you know.

                              Your reference to the pin appearing peened as though somebody had tried to remove it before makes me wonder if the pin was in fact a taper pin when it left assembly. It might have been some pin that could be made to function with a little riveting technique employed.
                              I'd be tempted to open up the small end hole 1 drill size at a time down to the shaft followed by some gentle hammer work.