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IndustryArena Forum > General Manufacturing Processes > Milling > Collet Not Locking to its Place
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  1. #1
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    Apr 2022
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    8

    Collet Not Locking to its Place

    Hello,

    I have a problem with an old Dynamyte EM-3116 mill. The collet is not locking properly to the quill when tightened with compressed air. The collet seems to lock at least almost properly when tightened at first. However, when the spindle is turned on, the collet drops down slightly for an unknown reason and the grip becomes loose. When the spindle is stopped the collet stays on the downward position and is not held tight.

    What could be the issue?

    Background: The collet holding screw was changed, although this is likely unrelated.

  2. #2
    Member
    Join Date
    Jan 2005
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    14720

    Re: Collet Not Locking to its Place

    Quote Originally Posted by CNCAndrew View Post
    Hello,

    I have a problem with an old Dynamyte EM-3116 mill. The collet is not locking properly to the quill when tightened with compressed air. The collet seems to lock at least almost properly when tightened at first. However, when the spindle is turned on, the collet drops down slightly for an unknown reason and the grip becomes loose. When the spindle is stopped the collet stays on the downward position and is not held tight.

    What could be the issue?

    Background: The collet holding screw was changed, although this is likely unrelated.
    Are you using the R8 collet system??

    The Draw Bar if changed would have to be the same length and have the correct Thread length, for the Collet to pull up tight in the spindle so this would be the first thing to look at as this is the part that pulls the collet into the spindle

    Remove the nut wrench on top, pull the Draw Bar out, and inspect to see if the threads are damaged, if you still have your old one compare the length

    The Threads on the Draw Bar need to be lubed with a moly grease
    Mactec54

  3. #3
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    Join Date
    Apr 2022
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    8

    Re: Collet Not Locking to its Place

    Quote Originally Posted by mactec54 View Post
    Are you using the R8 collet system??

    The Draw Bar if changed would have to be the same length and have the correct Thread length, for the Collet to pull up tight in the spindle so this would be the first thing to look at as this is the part that pulls the collet into the spindle

    Remove the nut wrench on top, pull the Draw Bar out, and inspect to see if the threads are damaged, if you still have your old one compare the length

    The Threads on the Draw Bar need to be lubed with a moly grease
    Thank you for the reply Mactech. It was only seen now (indeed the main page may not always contain the latest post).

    The collets look the same as in R8 standard (approximately 24mm in diameter and 18mm groove length), but the manual does not mention the standard. The drawbar has not ever been changed. Only the collet aligning screw at the bottom.

    I will try out the inspections you recommended.
    Last edited by CNCAndrew; 11-24-2022 at 01:40 PM.

  4. #4
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    Join Date
    Apr 2022
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    8

    Re: Collet Not Locking to its Place

    Issue was resolved!

    - Cleaned up and oiled the draw bar.
    - Changed the cables transmitting compressed air. On inspecting the drawbar, the observation was made they had become fragile like butter due to age etc.

    Thank you for help!

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