What are the difference of the 3 types famous CNC tool holders?

cnc cutting tool holders

CNC machining centers typically use many different types of CNC tooling holders, three of the best-known on the market today are BT collet holders, CAT tool holders, and HSK collet chuck. So, what are the specific differences between them? Kindly find the comparison table and details below.

TypesStandardTaperAccuracyStiffnessClampingWorking status
BTJapen7:24Poor axial accuracyRelatively poor siffnessOutside with Pull studNot suitable for high speed

Large mass and large stoke

CATUS7:24Poor axial accuracyRelatively poor siffnessOutside with Pull studNot suitable for high speed

Large mass and large stoke

HSKGermay1:10Excellent axial and radial accuracyExcellent staic and dynamic stiffness and 5 times than BT &CATClamping inside and the clamping force is 2 times than BT &CATSuitable for high speed       Low mass and stoke


bottle grip taper tool holders

Standard: BT stands for “bottle grip taper” and is marked by a tapered shank. It was developed in Japan.  CAT is the U.S. national standard and was developed by Caterpillar to standardize machinery.  The acronym “HSK” is the German abbreviation for “hollow taper shank.”

cnc tool holders

Taper: An HSK tool holder has a ratio of 1:10, compared to CAT & BT tool shank that have ratios of 7:24.

Remark: Regarding BT & CAT, we also call “steep taper” and they are both adual flange taper, but BT tools are often referred to as BT flange, and CAT toolings are called V-flange. The variations in flange configuration mean that CAT and BT tools are not interchangeable. If you are interested, kindly find the detailed comparison of BT40 VS CAT40.

steep taper tool holder

Clamping force and radial stiffness: Unlike conventional shanks (BT & CAT) with clamping outside with retention knobs (pull studs), an HSK toolholder is hollow and the clamping mechanism operates from the inside. Assuming that equivalent force is applied to the drawbar, twice as much clamping force is exerted on the flange of an HSK shank compared to a steep-taper shank. This extra clamping force makes the radial stiffness of HSK toolholders up to five times greater than the value for CAT and BT.

HSK tool holders

Dual Contact: CAT & BT CNC tools holder only have taper contact with the spindle while HSK is designed for both Taper and Flange contact the spindle. When we use CAT and BT toolling holder systems, since both engage the CNC machine with a single contact surface, there is a small gap between the tools holder and the spindle face. As machining spindle speeds have increased, centrifugal force pulls the tool shank toward the spindle, resulting in inaccuracies and tendency to lose accuracy. But the HSK toolholder contacts the spindle taper and flange on the spindle face to make a solid union in both the axial and radial planes.

cnc spindle tool holder

In operation, HSK tool holders are resistant to axial movement because the face contact prevents the toolholders from being pulled up into the spindle at high speed. So the HSK tool shank systems are becoming increasingly popular for their stability and balance in high-speed machining operations, which is now used and implemented with various types of HSM machines.

CAT tool holders

HSK tool shank designated as A through F and a total of 35 sizes. HSK tooling holder address three different application categories. Types E and F are designed for low torque and very high spindle speeds on machines that incorporate ATCs. Types A and C serve applications requiring moderate torque and moderate-to-high spindle speeds. (Type A is for automatic tool changing, and Type C is for manual changing.) Types B and D are designed for high torque applications with moderate-to-high spindle speeds. (Type B is for automatic changing and Type D is for manual changing.)

In addition, the CNC tool holder can be divided into collet shank, hydraulic tool holders and shrink chuck according to the different clamping methods and principles.

iso tool holders

At RicoCNC, there are several common styles & sizes of tool holders that we have below:

  • BT30 tool holder
  • BT40 tool holder
  • CAT40 tool holder
  • CAT50 tool holder
  • HSK63 tool holder

We also offer a large range of high quality and value priced CNC toolholder & pull studs & collets (ER & OZ & SK) & collect nuts & toolholder forks for the world marketplace, all parts are top quality, if any needs, welcome to contact us.

    Leave a Reply

    Your email address will not be published. Required fields are marked *