1/4 Galloway tapered keyway

Discussion in 'General Engine Discussion' started by blockmanjohn, Dec 16, 2017.

  1. Dec 16, 2017 #1

    blockmanjohn

    blockmanjohn

    blockmanjohn

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    Hi, I am about to machine the fly wheels for my 1/4 scale Galloway, and have a question about the keyway between them and the crankshaft. The plans call for a straight 1/8" keyway on the crankshaft and a tapered keyway on the flywheels held together with a tapered gib key. I have never broached a keyway before, but it doesn't seem too difficult. I have no idea how to broach a 1/8" per 12" tapered keyway on the flywheels except that you maybe do not press the last pass of the broach all the way through leaving a tapered keyway. Just guessing here. My other thought is to just cut them both straight and use a tapered key. If any one can help me with this I would greatly appreciate it. Thanks, John.
     
  2. Dec 16, 2017 #2

    rklopp

    rklopp

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    Make a special bushing with a slanted floor in the slot. Also ok to broach the flywheels straight and slant the shaft keyway, but that would not be prototype in my experience.
     
  3. Dec 17, 2017 #3

    Jasonb

    Jasonb

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    Thats the way I do it, turn up a bush pack up under one end of my vice by 1/16 over the 6" width of the mill table and mill the slot moving in Y direction.
     
  4. Dec 17, 2017 #4

    blockmanjohn

    blockmanjohn

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    Thanks for the help. I can do that. As for the key itself, does it have to be heat treated or can I just make it from mild steel and leave it? There can't be too much pressure on it. Thanks, John.
     
  5. Dec 17, 2017 #5

    rklopp

    rklopp

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    Heat treated is better, but soft will work. The problem with soft is that it will show every mark from banging it in or pulling it out, unless you are very careful to use a soft punch.
     
  6. Dec 17, 2017 #6

    bazmak

    bazmak

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    take the middle road and use key steel off the shelf
     
  7. Dec 18, 2017 #7

    BobsModels

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    John

    If you are going to be making more engines or anything with flywheels I suggest you take a day and make up a set of tapered sleeves for your broach set.

    Start by making a tapered master at the 1/8" per foot. I just used a piece of .312 x 2.3 x .5 scrap. Machined the angle. I then made up a set of bushing to match my set only I madethem longer about 1.6" under the head. When machining the slot just set your master under the bushing in the vice and you have the angle, just make sure it is tapering the correct direction.

    You now have a nice set. You can use the master angle when you need to make a key, again make sure you have it set the right direction. I make my keys with nub on the end so it can be pulled easily.

    Given everything is made from the same master it is irrelevant if the master is off slightly. Everything you make will be identical to that master and therefore will fit.

    Fixtures like these will just make everything go easy over the years.

    Good Luck

    Bob
     
  8. Dec 20, 2017 #8

    MachineTom

    MachineTom

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    I have broached keyways by making a Spud/bushing with a taper to match the flywheel taper. Cut a groove that fits the broach parallel to the tapered surface.

    Now place the Spud, with the groove side against the cutting table. Now after you cut it, the Spud will sit with the groove vertical, to allow a straight push of the broach.
    A bunch of work, but the Spud will hang around doing nothing until the next time it's needed.
     
  9. Dec 20, 2017 #9

    MachineTom

    MachineTom

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    I just reread the first post. Since the shaft and flywheel are straight bored. You need to machine the broach groove to the angle needed. The groove bring deeper at the end opposite the starting end.



     
  10. Dec 20, 2017 #10

    MachineTom

    MachineTom

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    I just reread the first post. Since the shaft and flywheel are straight bored. You need to machine the Spud broach groove to the angle needed. The groove bring deeper at the end opposite the starting end.



     
  11. Dec 20, 2017 #11

    MachineTom

    MachineTom

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    I just reread the first post. Since the shaft and flywheel are straight bored. You need to machine the Spud broach groove to the angle needed. The groove bring deeper at the end opposite the starting end.



     
  12. Dec 20, 2017 #12

    MachineTom

    MachineTom

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    I just reread the first post. Since the shaft and flywheel are straight bored. You need to machine the Spud broach groove to the angle needed. The groove bring deeper at the end opposite the starting end.

     

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