What is CAT Taper (CAT / V-Flange Taper)?

CAT taper identifies a family of 7/24 steep-taper, V-flange toolholder interfaces used on many machining centers. CAT40 and CAT50 identify different nominal sizes, but complete compatibility also depends on the flange, retention knob, machine requirements and installed tool-change system.

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Definition

CAT Taper (CAT / V-Flange Taper)

What is a CAT taper?

CAT taper identifies a family of 7/24 steep-taper, V-flange toolholder interfaces used on many milling machines and machining centers. The spindle locates the holder on the taper, the flange supports automatic handling, and a retention knob or pull stud allows the drawbar to retain the holder.

CAT40 and CAT50 are different nominal sizes. CAT50 tooling generally supports larger, heavier-duty applications, but the machine's spindle, speed, torque, tool changer and process determine the practical fit. A taper-size label alone does not establish full compatibility.

What to verify before buying tooling or a machine

Interface details

Confirm the taper size, flange form, balance requirement, maximum tool limits and machine-builder specifications.

Retention system

Use the correct retention knob or pull stud for the spindle and holder. Similar-looking parts are not automatically interchangeable.

BT and CAT holders share a 7/24 steep-taper concept in corresponding sizes, but their flange geometry and retention arrangements differ. Verify the complete interface rather than relying on taper contact alone.

Sources and further reading

ASME — 7/24 taper tool-to-spindle connection reference provides standards context for automatic tool-change interfaces. Always follow the machine and toolholder manufacturers' current instructions. See the Machine Blue Book methodology.