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Round keyway question.

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    lazlo
    Senior Member

  • lazlo
    replied
    Originally posted by clutch
    Well I sure don't see anything wrong with Dutch pins.
    So is a Dutch pin (key) the same thing as a Scotch key?

    Leave a comment:

  • Swarf&Sparks
    Senior Member

  • Swarf&Sparks
    replied
    I recall from some part of my mis-spent youth, a heavy machinery coupling using 3 tapered pins.
    The setup was 3 tapered "keyways" with 3 tapered pins.
    Each pin had an adjusting screw to drive it tighter into the matching taper, removing any sign of lash. This was part of PM.

    Anyone encountered these couplers, or has my fading memory combined two different couplers?
    These were on some very high torque applications in heavy industry.

    Leave a comment:

  • Carld
    Senior Member

  • Carld
    replied
    Round keys are very strong. I built several barrel stave cutting machines and we used a cutter head with many staged insert cutters and it required two round .500" round keys at 180 deg from each other on the shaft. I had to cut the shaft with a round nose endmill and compute the depth of cut so there was no slop. I think I built 5 machines and it was alway tricky to get the shaft keyways just right with no slop. The cutter head was powered by a 10 hp motor if I remember correctly and swung from side to side as it cut the stave.

    A Dutch or Scotch pin is usually a tapered pin installed as shown in the opening thread photo. I always used a set screw in place of a pin and locked the set screw with locktite. I never had one fail or escape.

    Leave a comment:

  • oldtiffie
    Member

  • oldtiffie
    replied
    "Pinned"

    I am quite unbiased.

    I appreciate a good pair of pins no matter what the nationality.

    Leave a comment:

  • clutch
    Senior Member

  • clutch
    replied
    Well I sure don't see anything wrong with Dutch pins.

    1. Because I have Dutch heritage.
    2. Because I'm repairing a cracked varidrive sheave and used them.



    Clutch

    Leave a comment:

  • oldtiffie
    Member

  • oldtiffie
    replied
    "Touchy ain't they?

    Originally posted by Originally Posted by oldtiffie
    Yep. AKA "scotch key"
    Originally posted by lazlo
    What's the difference between a Scotch Key and a Dutch Key?

    By the way, there was a thread over at PM awhile ago, and a Scottish member was quite offended at the reason given by an Aussie for why they're called Scotch Keys
    This one?
    http://www.practicalmachinist.com/vb...3&postcount=29

    Leave a comment:

  • dp
    Senior Member

  • dp
    replied
    Originally posted by oldtiffie
    Hi Dennis.

    If a square key is "male" to both the "driver" and "driven" the square key can develop a "rocking" motion in its "slot/s" (keyways) if the shaft/coupling is oscillating.
    Quite so, Tiffie - on every large system I've worked with there's always been a set screw on the key to prevent that problem. Even so you can very often see the tell-tail line on an old key that indicates it's been moving around. The old shaper I'm restoring has an interesting combiination of woodruff and square keys. Mostly because of the conversion from belt drive to v-belt drive. The woodruff key is left floating in an adapter collar and the setscrew sets against the shaft. I think I'll rework that so it doesn't bugger up the shaft any more than it has. The babbit bearings will appreciate it when it comes time to yank out the bull gear.

    Leave a comment:

  • Guest
    Guest

  • dewat
    Guest replied
    Thanks for the info guys, I thought it would work but hadn't seen anything other than the one brief mention. I managed to get a dowel pin in it, its nice and tight just difficult to work with such a small pin.

    Oldtiffie "It beats the hell out of making internal and external key-ways!!!"

    LOL that exactly what I was trying to avoid, plus I have to make sure its indexed to the ratchet mechanism on the other end.

    Thanks, Jim

    Leave a comment:

  • lazlo
    Senior Member

  • lazlo
    replied
    Originally posted by oldtiffie
    Yep. AKA "scotch key"
    What's the difference between a Scotch Key and a Dutch Key?

    By the way, there was a thread over at PM awhile ago, and a Scottish member was quite offended at the reason given by an Aussie for why they're called Scotch Keys

    Leave a comment:

  • Guest
    Guest

  • juergenwt
    Guest replied
    Works very good. Use it (among other things) to repair a stripped threaded hole with a threaded plug of a larger size and a round key to hold the threaded plug in place.

    Leave a comment:

  • oldtiffie
    Member

  • oldtiffie
    replied
    The key to it all??

    Originally posted by dp
    A square key transmits energy tangentially to the next component. Round keys exert a force away from the center to the next component. It probably won't matter right away if the key is square or round. I do wonder what would happen with an oscillating shaft over time, though.
    Hi Dennis.

    If a square key is "male" to both the "driver" and "driven" the square key can develop a "rocking" motion in its "slot/s" (keyways) if the shaft/coupling is oscillating. A Woodruff key is often better because of its depth of embedment (usually) in the "shaft". Multiple keys are often better than one. The optimum perhaps is a spline with perhaps the "involute" spline/d shaft or its derivatives being best and its mating (usually) "broached" mating (female) coupling/gear etc.

    As said, a round key is surprisingly adequate. They are often designed/meant as a "weak link" (mechanical "fuse"?) to ensure shearing-off before the gear train or what ever is over-loaded.

    Leave a comment:

  • Paul Alciatore
    Senior Member

  • Paul Alciatore
    replied
    I could be wrong, but I believe I read that round keys are stronger because they avoid the stress risers that the square key slots create in both the shaft and the wheel/knob at the corners. As for the keys themselves, size for size, the shear strength should be close to the same.

    Leave a comment:

  • gmatov
    Senior Member

  • gmatov
    replied
    We used the same in the Westinghouse for some pretty damned big couplings.

    Inch and a half on the big end of tapered pins, holes cleanly reamed, and the pins soaked in liquid nitrogen, driven home, and allowed to warm up.

    Don't think there was a one that ever let go. 1,000 HP and up motors, to boot.

    Small couplings, it works just as well.

    The fact that we used round, tapered pins for larger HP motors/generators, and square keys for lower HP, makes me think that the round pins are better.

    Of course, million KW generators, did use square keys. They also speed up quite a bit slower than a 10,000 HP motor does. 0 to 3600 in a couple seconds, versus 10 minutes, mebbe, to get 200 tons of rotor turning in a generator.

    Cheers,

    George

    Leave a comment:

  • dp
    Senior Member

  • dp
    replied
    A square key transmits energy tangentially to the next component. Round keys exert a force away from the center to the next component. It probably won't matter right away if the key is square or round. I do wonder what would happen with an oscillating shaft over time, though.

    Leave a comment:

  • torker
    Senior Member

  • torker
    replied
    Tiffie.. I always wondered if there was a proper name for round keys.. thanks!
    Dewat... what the heck are those fancy lookin gizmos for?
    Russ

    Leave a comment:

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