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  1. #1
    Join Date
    Aug 2007
    Posts
    105

    GB alignment key sheared off!

    Hi all, I have a citizen L20 that somehow the little key inside the Guide Bushing sleeve sheared off. Does anyone have an easy way to take the remainder of the key out so i can put a new one in?? Looking at the manual it looks as if I have to take the WHOLE (&#(!!# GB assembly completely apart to get at the pin, which seems totally ridiculous.

    just hoping someone else has an easier way!
    thanks!

  2. #2
    Join Date
    Jun 2010
    Posts
    46
    Yes you have to pull the whole assembly apart and knock the the pin out and replace with a new one but refer to parts manual for pin depth as this is important.
    Also note how the bearings are mounted in the guide bush assembly as they have to be put back the same place to help maintain balance and the thrust bearings in the correct direction.

  3. #3
    Join Date
    Feb 2008
    Posts
    267
    Quote Originally Posted by dookie2022 View Post
    Yes you have to pull the whole assembly apart and knock the the pin out and replace with a new one but refer to parts manual for pin depth as this is important.
    Also note how the bearings are mounted in the guide bush assembly as they have to be put back the same place to help maintain balance and the thrust bearings in the correct direction.
    I'll take that one step further.
    I would suggest that if you have the bearing out, to just replace them with new.
    It's going to take an hour to get everything apart and disassembled, you might as well spend the $220 buck and put new in.
    Not to mention that these rarely just "shear" off.
    It's usually the result of some type of catastrophe which most likely caused some bearing damage; even if the seem ok now.
    But that's just me.

    Good Luck.
    Control the process, not the product!
    Machining is more science than art, master the science and the artistry will be evident.

  4. #4
    Join Date
    Jun 2010
    Posts
    46
    Personally if the bearings do not need to be replace I would not.
    To get the same bearing life as a factory setup you have to grind spacers to the correct size to maintain the correct loading on the bearings as this is usually done by spindle repair personale who are familar with bearing loads and the amount of grease and type of grease to use.

    These load settings are secert to the machine tool manufacture.
    I have seen companies just change the bearings and they only last about one to two months before needing to be replaced again.
    I would think twice about bearing replacement.

  5. #5
    Join Date
    Feb 2008
    Posts
    267
    Quote Originally Posted by dookie2022 View Post
    Personally if the bearings do not need to be replace I would not.
    To get the same bearing life as a factory setup you have to grind spacers to the correct size to maintain the correct loading on the bearings as this is usually done by spindle repair personale who are familar with bearing loads and the amount of grease and type of grease to use.

    These load settings are secert to the machine tool manufacture.
    I have seen companies just change the bearings and they only last about one to two months before needing to be replaced again.
    I would think twice about bearing replacement.
    That's a good point about the pre load.
    One should certainly NOT replace bearings if they do not know what their doing.
    As far as the pre load dimension being a "secret", right around .001" is a good rule of thumb.
    Your best bet is to measure all the (old)bearings and spacers widths to get a "stack" dimension, then replicate that as closely as possible with the new.
    Control the process, not the product!
    Machining is more science than art, master the science and the artistry will be evident.

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