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  1. #1
    Join Date
    Jan 2007
    Posts
    114

    Cat 40 compatibility with BT 40

    I have a Bridgeport VMC 760 and it has ca CAT 40 Spindle, I have a line on some BT 40 toolholders, but I am not sure if they will fit. Any advice would be welcome.

    Thanks
    Endmill

  2. #2
    Join Date
    Jul 2005
    Posts
    12177
    If you have a toolchanger no, the flanges are different. As far as I know the taper is the same and the pull studs are the same; I bought a machine which was configured for BT40 and the only thing that needed changing to convert it to CT40 was the toolchanger arm that gripped them on the flange.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  3. #3
    Join Date
    Aug 2005
    Posts
    1622
    Something with the orientation keys are also different. The CAT40 has both keys the same size. The BT, one key is larger or offset. So, in effect, you can get away with a CAT40 in a BT, but not a BT in a cat spindle without mod's either to the holder or the orientation keys. Beware of only one key driving, could induce odd wear in the taper long term. Getting them to fit the spindle won't be much of a gain if the tool changer is incompatible.

    DC

  4. #4
    Join Date
    Nov 2006
    Posts
    925
    DC,you have it the wrong way round.The CAT40 has one keyway shallower than the other which means it won`t fit in a BT spindle with both drive dogs fitted.As for driving on one key,I have a Rambaudi turret mill (twice the weight of a Bridgeport) which has worked with one key for years with no ill effects.This allows me with a selection of drawbars to use 40INT,BT40 and CAT40 holders in the machine.

  5. #5
    Join Date
    Jul 2005
    Posts
    12177
    Like I said the only thing that was changed to go from BT to CT was the toolchanger arm; the keys on the spindle are the same for both types.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  6. #6
    Join Date
    Aug 2005
    Posts
    1622
    I knew SOMETHING was different with the keys in one direction or the other. (nuts)

    Thanks for clarifying the differences as a backup to unintentional mis-information!

    DC

  7. #7
    Join Date
    Jan 2007
    Posts
    114

    Thank you

    Thanks for the input that is exactly what I was hoping for, I will buy then and let you all know how it turns out.

    Endmill

  8. #8
    Join Date
    Nov 2006
    Posts
    925
    The keys on the spindle are not the same for both types,although they can be modified for both types.Next time you pick up a CAT holder look at the keyways from the small end of the taper and you will see the difference.

  9. #9
    Join Date
    Jul 2005
    Posts
    12177
    Quote Originally Posted by gridley51 View Post
    The keys on the spindle are not the same for both types,although they can be modified for both types.Next time you pick up a CAT holder look at the keyways from the small end of the taper and you will see the difference.
    This probably explains why my machine only needed the toolchanger arm switched. BT 40 will go into a Cat 40 spindle but CAT 40 will not go into BT 40 spindle.
    An open mind is a virtue...so long as all the common sense has not leaked out.

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