Cat 40 compatibility with BT 40

[inertialabs]

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

[Geof]

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.

[One of Many]

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

[gridley51]

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.

[Geof]

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.

[One of Many]

I knew SOMETHING was different with the keys in one direction or the other.

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

DC

[inertialabs]

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

[gridley51]

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.

[Geof]

Originally Posted by gridley51 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.