[reedmiles]

I have only used r-8 and ntb-30 tool holders I was wondering what the difference between bt and ct holders is

[Caprirs]

The taper is identical. BT and Cat V will physically fit in the same spindle. However, BT uses a metric threaded retention knob and Cat V uses an inch thread. Also, the flange parts of the toolholders are slightly different so they typically are not interchangeable in the tool carousel/magazine.

So on a machine equipped for BT40, I could manually load a Cat V 40 toolholder into the spindle, but I could not run the automatic tool change.

[reedmiles]

thank you for the information

[laka]

As far as I know, BT spindles have two drive keys and CV spindles have only one key. And a CV tool probably wouldn't fit in a BT spindle since it doesn't have clearance for two drive keys.

[fpworks]

As far as I know, BT spindles have two drive keys and CV spindles have only one key. And a CV tool probably wouldn't fit in a BT spindle since it doesn't have clearance for two drive keys.

Actually, they both have two drive keys. The BT holder has symmetrical drive slots and the CAT specification has one deep and one shallow drive slot. On most newer machines, the spindle drive keys will accomodate either BT or CAT toolholders. (and CAT toolholders can be oriented at 0 or 180 degrees in the spindle)

In addition to what has already been mentioned, there is another difference that affects larger tools. After the flange (away from the spindle), the BT specification is "open" in regards to holder diameter. However, the CAT specification requires that the toolholder neck down immediately after the flange, for a specific distance. (This was part of the original CAT spec to accomodate very early tool changers. Not required for any modern tool changers, but this part of the standard remains.)