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Limits of keyways

  1. May 6, 2014 #1
    Hello guys, first post here so don't get mad if I have place it in the wrong area.
    Going through one of my lessons earlier I was learning about the limits and fits of holes and shafts, determining the tolerances of certain objects kind of stuff. It was also briefly mentioned that you could determine the limits of keyways by using a similar process, this was not gone into in great detail so I do not really understand it a whole lot. What is the process for determining limits of keyways if you just know the width of it?
    I am sorry if I have been a little vague, but I was not sure how else to explain it.
    Thanks, Thrag.
  2. jcsd
  3. May 6, 2014 #2


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    Welcome to PF.

    There are cases where the joint is tight and the key is only critical during assembly as an angular relationship must be maintained. The accuracy of key fit then decides accuracy of assembly. Often on machine timing shafts a semicircular woodruff key is used with a locking taper shaft coupling. http://en.wikipedia.org/wiki/Key_(engineering)#Woodruff_keys

    There are other cases where the key transfers mechanical energy, usually through a long rectangular parallel key. If parallel keys do not fit well in their ways then the movement will repeatedly hammer or slog out the key and/or it's way. This is a very common mode of failure in mechanical equipment. The quality of the machinined fit of shaft, key and pulley decide the lifetime of the equipment. http://en.wikipedia.org/wiki/Key_(engineering)#Parallel_keys

    Refine your question if you require a more refined answer.
  4. May 10, 2014 #3
    I would say could you explain a bit more on what you mean by the 'limits of keyways' ? Are you talking about its dimensions ? Generally keyways for a certain shaft size are found in standard charts employed by OEMs.
  5. May 10, 2014 #4
    I am sorry if it my question wasn't very specific, this is not a topic I know a huge amount on.
    Yes I am talking about dimensions, where would I be able to find out more about the standard charts employed by OEM's? I had a quick search but was unable to find anything that seemed related.
    Thank you for the links Baluncore, they have really clarified the topic for me!

  6. May 11, 2014 #5


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    Machinery's Handbook, 28th Edition, has a section on “Keys And Keyseats”. It includes tables with tolerances.
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