CV, DV and BT tapers are all identical and known as 7/24 tapers. These tapers are commonly referred to as a “self-releasing” or “fast tapers.” The primary differences between the toolholders are the flange design and retention knob threads.

CV Toolholders
CV is often referred to as “CAT” or Caterpillar V-flange tooling as described under ANSI B5.50, and typically has inch threads for the retention knob. Some CV holders have a counter bore for a piloted retention knob. This is typically used in higher spindle speed applications.

(see attached PDF file for CV tool chart)

BT Toolholders
The BT taper is a JIS B6339 specification (Japan Industrial Standard). BT tooling carries a wider flange than a CV or DV tool and contains metric retention knob threads.

(see attached PDF file for BT tool chart)

DV Toolholders
The DV taper is specified under DIN69871 (Duetch Institute of Normalcy). The DV tool is very similar to a CV toolholder, but has a V-shaped orientation notch that is perpendicular to the groove that is machined in the diameter of the flange. DV toolholders also contain metric retention knob threads.

(see attached PDF file for DV tool chart)

CV tooling is the most utilized tooling in North America, but machine builders globally generally build their equipment based on the specification of the country of origin.

Although the tapers are identical between the CV, DV, and BT tooholders, they are not interchangeable with one another because of the variations in flange dimensioning. Because the tool changer arm uses the flange to grab onto to index the tool, therefore damage could occur if you tried to interchange the tools.

Technical Tip #128 - CV, BT & DV Toolholders

1. Remove all grease from the hydraulic chuck and cutting tools before using.
2. Insert the cutting tool into the clamping bore as far as the stop pin /stop screw will allow.
3. Adjust the cutting tool length with a hex wrench.
4. Always hand-tighten the clamping screw with a hex wrench as far as the stop limit. Never try to adjust the stop pin when the hydraulic chuck is in the clamping position.
5. For best accuracy, use a round shank (no flats) with h6 tolerance and no bushing.
6. Weldon shanks can be gripped without reducer collets, ¾” (20 mm) maximum diameter. However, the use of reducer collets for all flatted shanks is recommended. 

Technical Tips #129 - Using Hydraulic Chucks